Multi-Faceted Analysis of Airborne Noise Impact in the Port of Split (III)

Abstract

Marginal and neglected until recently, noise pollution is a significant topic of sustainable development today. Port noise has become an increasingly critical problem for the environment. The public and the scientific community have gradually become aware of the harmful impact of noise emissions on residents living near port facilities. It coincides with the increase in complaints from the population about excessive noise pollution in ports, especially in residential areas near the cargo terminals in Split. This paper seeks to empirically investigate overall port noise and assess the significance of the reported disturbances. The methodology includes the measurement of noise in zero state conditions, residual noise and noise during specific work processes, and consideration of conditions for possible adjustments of the selected work process during transport operations. The goal is to propose plans for noise reduction by evaluating the results of noise monitoring with the specified limit values, which determine the highest permissible noise levels for industrial and residential zones in the observed area. The values exceed the maximum permitted noise levels during the night. However, this problem can be reduced through operational and technical adjustments in cargo handling processes, acting as objective mitigation measures. The effectiveness of the defined procedure is demonstrated by its application in the Port of Split, contributing to the port’s sustainability located near the residential area.

1. Introduction

Seaports are essential nodes in the global supply chain, generating positive socioeconomic effects in the specific region; however, they may also generate potentially adverse environmental consequences [1]. Given the significant ecological pressures caused by ports in neighboring urban areas, the issue of port noise has become a major public concern, particularly where there are substantial marine operations and frequent handling of cargo [2]. Furthermore, considering that noise pollution is one of the top ten environmental priorities for European ports in defining key environmental areas to be addressed [3], it is anticipated that ports will enlarge their areas and related traffic. This could result in an increase in port noise, emphasizing the importance of considering noise effects in future infrastructure development plans. The scarcity of research on the social impacts of port operations can be attributed to the unclear boundaries and subjective interpretations of social indicators, which hinder the measurement of the effects of port social performance [4]. The confirmed negative effects of environmental noise on human health have been extensively documented in the literature, such as the hearing consequences of long-term exposure to noise levels above 85 dB(A) [5,6] and the non-auditory health effects of ongoing exposure to noise levels ranging from 45 to 65 dB(A) [7,8]. The most prevalent problems include annoyance, disturbed sleep, cognitive impairment, behavioral and emotional disorders among children and adolescents, depression and anxiety, heightened physiological stress responses, endocrine imbalances, and cardiovascular diseases accompanied by hypertension [9]. Furthermore, noise can have a considerable impact on diminishing the quality of life and, consequently, the value of real estate properties in residential areas [10]. Only recently has port noise gained more public and academic attention due to some international projects aiming to solve the rising number of citizens’ complaints about the effects of airborne port noise [11]. These complaints have been reported in different ports [12], such as Dublin [13], Athens [14], Barcelona [15,16], La Spezia and Nice [17], and Split [18]. Hence, there is a growing interest and concern among local communities that are directly exposed to noise pollution from ports [19].

Therefore, to empirically examine the overall port noise, this study was based on noise monitoring of cargo terminals during the transport-related operations in the Port of Split in order to determine the sound pressure levels for the day (L_day), evening (L_evening), and night (L_night) hours. The aim is to propose mitigation plans by comparing the obtained results with the specified threshold values, which define the maximum allowed noise levels for both industrial and residential zones in the surveyed area. As for the scarcity of results generated from similar case studies dealing with the increasing resident complaints about the harmful effects of port noise, which is currently limited to several ports, the intention is to make the outcomes of this research generally applicable. This primarily includes drawing empirically validated suggestions and recommendations, which could be suitable for the application of noise mitigation measures in the port areas dealing with similar challenges. The small sample of ports analyzed in the academic literature from a noise pollution standpoint and growing public pressure indicate the importance and relevance of this research as well as its practicality. The expected outcomes of this research could be used as a base for applying noise mitigation measures according to the specific aspects of port operations and port noise sources.

The current research follows the outcomes of the project NOIPOS [20], which deals with the measurement and validation of the environmental noise in the Port of Split (Croatia), divided into three project activities, and a regulative overview, forming a holistic model. The introductory activity of the project included the comprehensive analysis of the external airborne noise from shipping, including port noise, from the regulation’s standpoint. It has been confirmed that the efficient noise management and implementation of noise protection measures in maritime industry is lacking, displaying a deficiency when considering the legal basis, including the legal framework in Croatia [21]. The first project activity dealt with the identification and classification of the noise sources in the Port of Split. Additionally, the authors considered the overview of the noise strategic maps in the examined area, provision of simulations of noise propagation in the area from the ships berthed in port, and assessment of the total external costs raised from the port activities, calculated as averages based on the relevant literature. The primary intention of this project phase was to identify principal noise sources and the theoretical propagation of noise in open space from the perspective of a monetary evaluation, as well as the assessed intensity impacting the proximity of inhabited areas [22]. As for the increasing number of complaints about port noise, the second project activity included the assessment of resident’s perception of the sound-pressure levels generated from various port-related activities by conducting a survey in the area most affected by port noise. The residents dominantly perceived the adverse noise effects from port noise, indicating the harmful effects and highly rated noise intensity for the day–evening–night levels, especially emphasizing the noise disturbances during night. However, as for the restricted knowledge regarding port noise and subjective standpoints in the assessment of noise emission from the port, psycho-physical and emotional states should be included in the validation of the final results [18]. In order to validate the research findings generated from the previous project activities, the present work intends to finalize the concept of the project, aiming to determine the sound pressure levels in the two residential areas in the vicinity of the port during the day, evening, and night by noise measurement of the cargo terminals. The current study leans on the results of the previous project activities, comprising the results of simulations of noise propagation from ships at berth and the assessment of residents’ perceptions of the sound pressure levels generated from various port-related activities, comparing them with the results generated by noise measurement. These arguments were the fundamental motives for conducting the measurement campaign of noise emissions.

2. Literature Review

Noise from complex transport assets, such as in seaports, creates a challenging measurement environment [17]. This is due to the coexistence of various industrial, logistical, and traffic-related activities. The prevalence of numerous port noise sources and their interaction with related transport infrastructure [23] leads to significant complexity in determining the contribution of each individual source to the total residual noise. Consequently, identifying noise sources that exceed government-prescribed permissible noise levels is difficult. Technically, noise assessment encounters challenges with source identification and characterization [24]. However, these limitations are mainly a result of the marginalization of port noise at the regulatory level. Port noise is classified as industrial noise, which hinders the adoption of international noise management standards [21]. Furthermore, the provision of strategic noise maps, as outlined by the Environmental Noise Directive (END) [25], has omitted port noise, ignoring its harmful impact on the population residing near the port area [26]. Due to the significant residential exposure to low-frequency noise emitted by ships in port [14], some authors have suggested that the main noise challenges in ports arise from the direct and indirect noise emissions caused by ships [27]. In a similar vein, Schenone et al. [2] indicated the importance of adopting mitigation actions for traffic noise at Tripoli port, emphasizing the mandatory nature of the reduction in noise levels emitted from road vehicles and specific components of road surface. However, Dragan and Mulej [28] argued that multiple factors play a role in determining the level of noise produced by ports over an extended period in a given area. These elements comprise the topography, details of the port locality, port operations, and geographical placement. Furthermore, Biot et al. [29] have studied factors for the assessment of noise emitted by cruise ships in ports by application of an additional class notation issued by the Lloyd’s Register in 2019. The authors have concluded that the introduction of methods by ship classification societies to assess outdoor airborne ship noise is valuable; however, the application of these proposed evaluation techniques in the field raises many issues. During navigation and maneuvering procedures while approaching the port, noise from large ships can significantly affect the local population and the natural environment [30]. Ships are getting bigger, as are the number of sound sources, so Di Bella et al. [31] advocate the development of measurement techniques specific to a specific vessel or operational procedure. Coppola et al. [32] have studied airborne noise emissions originating from a ferry ship at the port of Naples, where they created a tool for the prediction of the acoustic impact generated by the ferry at the port. Vukić et al. [22] provided a comprehensive literature review of the most relevant studies considering the effects of noise in the maritime industry, showing the importance of noise mapping and the need to adopt a universal noise management protocol to standardize the measurement and validation of noise assessments. It should be noted that despite the effects of noise mapping as a mechanism for the periodic evaluation of citizens’ exposure to increasing noise effects of the main transportation infrastructures, the implementation of noise monitoring networks was found to be valid and suitable for fulfilling the increasing requirements for frequent evaluation of noise emissions from primary noise sources in port [33]. The most critical stage in assessing noise is identifying the dominant noise sources. Baclet et al. [34] have introduced “noise exposure sensitivity maps” for the road transport sector that enable the identification of various issues and opportunities for noise mitigation involving multiple stakeholders; these maps can serve as a qualitative tool to assess the most sensitive areas within a city, where mitigation measures could be particularly effective. However, operating in a complex port environment within the context of a crucial noise mitigation strategy can be challenging [35].

3. Materials and Methods

3.1. Research Settings

The Port of Split was selected as a case study for noise measurement due to the complex geographical location of its cargo terminals close to two residential areas. As citizens’ complaints increased, this work investigated whether they corresponded to an increase in noise pollution from various port, traffic, industrial, and logistical sources, as well as other sources. The setting of this research considered the occurrence of diverse noise sources in the examined areas generating specific sound pressure levels. Due to the inability to isolate individual noise sources from cumulative values, the authors assessed the total noise according to the research settings.

The concept of this study has been divided into four connected measurement segments:

• The A-weighted sound pressure level measurement (L_Aeq) of the initial state of port noise in the absence of cargo-handling operations (and other port-related sources);
• The A-weighted sound pressure level measurement (L_Aeq) of total residual noise, including the cargo-handling operations (and other port-related sources);
• The maximum sound level with A-frequency weighting and fast time weighting during the measurement period (L_AFmax), considering the noise emitted from diverse conditions of working processes realized in port (selected scenario) during night periods (L_night);
• The A-weighted sound pressure level measurement (L_Aeq) during night (L_night) of an open working process (selected scenario) considering two specific conditions:
• The setting of an acoustic cover or enclosure implementation to the existing cargo-handling equipment;
• Repositioning the conveyor system for handling bulk cargo inside the warehouse while conducting loading procedures.

3.2. Definition of the Noise Measurement Area

During July and September 2023, a noise measurement campaign at the receivers’ position was performed within the boundaries of the two inhabited areas surrounding the cargo port. The authors used a Class I sound level meter for the measurement process, which was compliant with IEC 661672-1 recommendations [36], combined with a weather station. This instrumentation was set at a specific location, with the microphone at 4 m height in the free field according to international standards [37,38]. Periods with rain events or with wind speeds higher than 5 m/s were removed. Measurement locations were determined as the areas primarily affected by the diverse activities in the port and other related traffic activities, which are realized in the vicinity of the cargo terminal in Split. The location of the first measurement was in the southern part of the cargo terminal (Brda district), near the border of the industrial and mixed, predominantly residential zone. It was necessary to examine the differentiation in equivalent continuous sound pressure levels with its A-weighted version (L_Aeq) between zones according to the threshold values prescribed by the Ordinance on maximum permitted noise levels, the type of noise source, time, and place of origin, individually for the day (L_day), evening (L_evening), night (L_night), and the day–evening–night levels (L_den) [39]

Table 1. Threshold values on maximum permitted noise levels according to the selected zones [39].

Zone	The Highest Permissible Rated Noise Levels LR,Aeq [dB (A)]
	Lday	Levening	Lnight	Lden
Zone of mixed, predominantly residential use	55	55	45	57
Industrial zone and zone of port areas	The noise level originating from noise sources within this zone and at the border with the nearest zone (e.g., residential or mixed zone), where the highest emission noise levels are expected; the noise must not exceed the permitted noise levels at the zone border.

shows the highest permissible rated noise levels for the two separated zones.

The radius of this study area falls in the range of 200–900 m from the farthest berth (Berth 1), while the terrain of the residential buildings rises progressively above the ground level of the port area. The traffic on the single carriageway, which separates the port area from the industrial and mixed zone, varies depending on the hours of the day. During peak hours, it could significantly contribute to the overall residual noise. The second location was northwestern to the cargo terminal, on the Vranjic peninsula. This location has an exclusively residential purpose, parallel to the port area, separated by the waterway, and exposed to direct noise emission from the industrial and traffic activities generated in the port and its surroundings. The distance between the inhabited zone and the most distant berth (Berth 5) ranges from 300 m (minimum) to 950 (maximum). The single carriageway within the district rarely influences the total noise of its local character. Figure 1 shows the situational features of the examined area, including the berth locations, residential and industrial zones (divided by a red dotted line), two southern districts (Brda), and the northwestern district (Vranjic) from the cargo terminals, position of the single carriageway, and measuring points.

The measurement equipment setting was performed according to determined measuring points (yellow points in Figure 1), which depend on the ship berthing spot and availability of access to certain positions because some optimal points, especially in the southern district, are privately owned. That occasionally interfered with the measurement process. The authors selected multiple measuring spots in both examined areas, as the geographical position of certain ones prevented the sight of the ships berthed at specific locations in port. That coincided with the radius change between the selected measuring point and dominant noise sources. Additional exogenous impacts considered while examining port noise levels included the meteorological conditions, especially temperature, wind speed, and direction, with continuously controlled air pressure and humidity. This enabled the integration of the external impact on the metrics of the noise measurement process.

3.3. Individual Features of the Working Process in the Port of Split

An examination of the sound pressure level was applied to the vessels calling the cargo terminals of the Port of Split in the determined time slots. The Port of Split has been designated as one of the most important passenger ports in the eastern Adriatic, while the cargo terminals have regional importance in providing services for local industry and regional logistics. The cargo facilities are located in the northern part of the city, close to the inhabited area comprising residential buildings and private houses. These specific locational factors and the configuration of the port basin contribute to the overall complexity of noise measurement and propagation in the open space. The main port basin has a semi-enclosed and narrow shape, where the cargo terminals are positioned on both sides, generating specific acoustic environment, especially toward the two inhabited areas located in the south (Brda district) and northwest (Vranjic district) of the cargo-handling operations. Figure 2, adapted from Vukić et al. [22], provides an overview of the cargo basin in the Port of Split, with a cross-section of the remaining cargo terminals. The highlighted section of the general port area represents the research sample of this paper.

As the working process in port is associated with transport-related activities, such as the cargo handled (number of cranes utilized) and ship type and size (duration of stay and berthing point), the authors examined these processes, which differed according to the specific cargo handled. The initial measurement and screening were conducted on a sample of eight ships carrying diverse freight. The conclusion was that the dominant sources obtained from measurements were those generally accepted, including the exhaust funnel of auxiliary engines and ventilation openings for the closed-working process and cargo-handling equipment (cranes) for the open-working process. These operations include the luffing and slewing processes, which determine the movement of a crane [1] and horizontal load movements, i.e., internal transports. These findings directed the flow of the empirical provision of this study. It meant that the working process of each cargo type handled was a reference point in selecting the research sample, regardless of the ship type and size. This argument was valid for the cargo manipulation process, opposite to the conditions of the berthed ship without the cargo handling operations in progress. Moreover, this condition was related solely to scenarios where the cargo loading and unloading process was carried out with the assistance of quay cranes while excluding the working process of the ship deck crane.

Table 2. Specific berthing spot characteristics in the Port of Split according to the set parameters.

Berth	Ship Type	Cargo Handled (Most Dominant)	Working Process
Berth 1	Oil/Chemical tanker	bitumen	closed *
Berth 2	Bulk carrier, General cargo vessel, MPV	scrap metal, yacht/catamaran	open **
Berth 3	Bulk carrier, General cargo vessel, MPV	petroleum coke, calcium, coal	open **
Berth 4	Bulk carrier	bulk slag, salt	open **
Berth 5	Bulk carrier, General cargo vessel, MPV	iron (wire, bars), copper concentrate	open **
Berth 6	General cargo vessel	grain, corn, other coarse grain	open **

* excluding the handling of port cranes (internal system). ** handling realized with the assistance of port cranes.

indicates the purpose of the individual berthing spots on the cargo terminal of the Port of Split, along with the most dominant cargo type handled and the nature of the working process.

According to the defined arguments and meeting the set conditions in this research, the authors carried out a set of noise measurements in a predefined selection of vessels entering the Port of Split.

Table 3. Specific vessel features based on selected criteria.

Ship Type	Cargo Type	Cargo Operation	Dwt * [t]	Loa * [m]	Beam [m]	Duration of Stay	Working Process
Oil/chemical tanker	Bitumen	Unloading	6180	110	18	5 days	Closed
Bulk carrier	Bulk slag	Unloading	55,446	188	32	6 days	Open
Bulk carrier	Calcium	Loading	39,090	180	30	3 days	Open
General cargo	Copper concentrate	Loading	27,263	180	27	2 days	Open
Bulk carrier	Bulk slag	Unloading	55,847	190	32	7 days	Open
General cargo/MPV	Yacht	Unloading	4432	112	17	1 day	Closed
Bulk carrier	Scrap metal	Loading	44,314	183	32	6 days	Open

* DWT—deadweight; LOA—length overall.

shows the specific vessel characteristics considered in this paper, along with the data on the type of cargo handled and operated, duration of the stay for completing cargo loading/unloading, and type of working process.

The measurements of A-weighted continuous sound pressure levels (L_Aeq) in [dB (A)] were provided individually for the day (L_day), evening (L_evening), and night (L_night), performing an hourly measurement sample for each determined period. As for the extended time of the day (12 h) and night periods (8 h) opposite to the evening period (4 h), which were previously defined in the Environmental Noise Directive [25], the authors repeated the measurement three times during the day, two times during evening period, and one time during the night to make final values more credible and precise. In the data-processing stage of research, the final results were determined as average values of individual parts of the day. The measurements of port noise interfered with the background noise of, primarily, road traffic and other industrial activities in the port, so the final values represent the residual noise.

3.4. Situational Analysis of Noise Measurement in the Examined Area

The specifics of individual measurements were presented by performing the situational analysis, thus providing all the characteristics of the measurement site and accompanying port operations. This enabled us to evaluate all the internal and external factors contributing to the final values and representing the port noise. The variable of the exact distance between the measuring spot and the noise source in the port primarily depended on the berthing location of the ship. The temperature, wind direction, and speed were measured with the accredited weather meter individually for day–evening–night levels, while the deviation between measurement locations were neglected. Furthermore, the differences between the meteorological conditions during the day, evening, and night times were negligible, especially when excluding the samples that exceeded the established limits. These values are indicated in

Table A1. Meteorological conditions registered during the measurement process.

Ship Type	Meteorological Conditions
	Temperature			Wind Direction	Wind Speed
	D	E	N		D	E	N
Scenario 1	32 °C	29 °C	25 °C	SW	6 km/h	4 km/h	4 km/h
Scenario 2	34 °C	30 °C	23 °C	SE	5 km/h	8 km/h	2 km/h
Scenario 3	33 °C	28 °C	26 °C	SW	8 km/h	5 km/h	5 km/h
Scenario 4	35 °C	32 °C	27 °C	NW	10 km/h	4 km/h	3 km/h
Scenario 5	33 °C	29 °C	23 °C	NW	5 km/h	5 km/h	5 km/h
Scenario 6	34 °C	30 °C	26 °C	SW	3 km/h	8 km/h	4 km/h
Scenario 7	32 °C	27 °C	24 °C	SE	7 km/h	10 km/h	8 km/h

(Appendix A). The terminal operator possesses two mobile quay cranes, which enable handling ships larger than 40,000 dwt, and a conveyor system for handling bulk cargo, primarily for loading purposes. This cargo-handling equipment is utilized individually or simultaneously, depending on the cargo type, based on the loading/unloading rate determined. During the closed working process of handling cargo, the other remaining equipment for loading/unloading purposes was used. The bitumen cargo unloading processes from the ship included a system of bitumen pumps and insulated pipelines, which were utilized for direct loading of the cargo to the bitumen truck tank. The ship deck cranes were used to unload the yachts and other smaller vessels from the ship deck to the terminal. These closed working processes generate lower sound-pressure levels but contribute to the overall port noise by generating noise emissions from the auxiliary engines (AE) and ventilation openings (VO). Additionally, during the measurement process, there were situations of several ships berthed in port, hence, several noise sources. However, as for the constrained port infrastructure and space, only one open working process (using mobile quay cranes) of larger ships (>20,000 dwt) is possible in port, and the closed working process mainly depends on the availability of the dedicated berth. Based on the above, the dominant noise sources during transport-related activities of cargo handling operations on berth are quay cranes, while the noise emissions of the ships’ AE (generators) and VO principally contribute to overall port noise. As for the specific character of scrap metal, during the handling process, the noise exponentially increased when lifting and dropping the cargo, especially during the first contact between the clamshell grab and the metal. The noise emissions from traffic and other noise sources generated in the port surroundings contributed to the increase in these value levels.

Working hours as a parameter are a significant feature because the perceptions of the population living near the cargo terminals in the Port of Split indicated the dominance of excessive noise emissions during night hours [18]. During the time slot dedicated to cargo-handling operations, the working process was not continuous, as there were numerous intervals utilized for repositioning the cranes (depending on the ship hold processed), trimming the cargo, delays caused by the unavailability of the truck or railcar for loading/unloading purposes or just for regular breaks. Finally, the other port-related noise sources, excluding the traffic on main roads surrounding the examined area, primarily included the circulation of trucks in the distribution of the unloaded cargo to the final destination (bitumen tank trucks), truck transportation of cargo to the background warehouses, and the background noise which consisted of industrial, logistical, and other activities in the port area. The noise emission from these background sources strongly influenced the total residual noise levels.

Table 4. Situational analysis categorized by the fundamental specifics of conducted measurements.

Scenario	Cargo Handled	Berth Number	Distance from the MICROPHONE (in m)		No. of Cranes in Operation	Dominant Noise Sources on Berth		Working Hours (Cargo-Handling Ops)	Other Port-Related Noise Sources
			S *	NW **		S *	NW **
Scenario 1	Bitumen	Berth 1	305	300	N/A	AE and VO	AE and VO	9:00–19:00	Bitumen tank trucks
Scenario 2	Bulk slag	Berth 3/4	340	560	Two cranes	Crane	Crane	00:00–24:00	HGV ***
Scenario 3	Calcium	Berth 4/5	360	740	One crane + conveyor	Crane	Crane	00:00–24:00	Background noise
Scenario 4	Copper concentrate	Berth 4/5	360	740	One crane	Crane	Crane	00:00–24:00	Background noise
Scenario 5	Bulk slag	Berth 3/4	300	560	Two cranes	Crane	Crane	00:00–24:00	HGV ***
Scenario 6	Yacht	Berth 2	360	400	N/A	AE and VO	AE and VO	9:00–19:00	HGV ***
Scenario 7	Scrap metal	Berth 2	360	400	One crane	Crane + cargo	Crane + cargo	7:00–23:00	Background noise

* S—southern residential area (Brda district). ** NW—northwestern residential area (Vranjic district). *** HGV—heavy goods vehicle.

shows the situational analysis of conducted measurements.

4. Research Results

4.1. Noise Measurement at the Receivers’ Position

Initially, the authors determined the baseline (zero state) conditions considering the level of noise emitted from basic port operations and other noise sources. In the absence of cargo-handling operations, there were high variations in the category of other noise sources’ emissions. The sound pressure levels of the zero-state residual noise from the inhabited areas included in this study, for day, evening, and night levels, are shown in

Table 5. A-weighted sound pressure level (L_Aeq) of total residual noise based on the zero-state conditions.

Day (Lday) [dB (A)]		Evening (Levening) [dB (A)]		Night (Lnight) [dB (A)]
S *	NW *	S *	NW *	S *	NW *
44.2	45.3	42.7	42.2	41.3	40.4

* S—southern residential area (Brda district); NW—northwestern residential area (Vranjic district).

. The final results represent the average values of three day samples, two evening samples, and one night sample with a measurement duration of one hour per sample.

Traffic density on the main roads surrounding the two examined residential areas while conducting the measurements according to the different parts of the day is shown in

Table 6. Traffic density on the main roads surrounding the two examined residential areas according to time and density criteria.

Cargo Handled	South from the Cargo Terminal (Brda District)			Northwest from the Cargo Terminal (Vranjic Peninsula)
	Day	Evening	Night	Day	Evening	Night
Bitumen	Heavy *	Medium *	Low *	Medium	Low	Low
Bulk slag	Medium	Heavy	Medium	Low	Medium	Medium
Calcium	Medium	Low	Low	Low	Medium	Low
Copper concentrate	Heavy	Medium	Medium	Heavy	Medium	Low
Bulk slag	Low	Low	Medium	Medium	Low	Low
Yacht	Medium	Medium	Low	Medium	Low	Low
Scrap metal	Heavy	Low	Low	Low	Low	Low

* applies to all of the above: heavy—high density, congested road (convoy driving); medium—medium density, average congestion (fluent traffic); low—low density, no congestion (occasional vehicle pass-by).

. During the measurement process, the authors monitored the road traffic activities, determining the share of passenger cars, motorcycles, and HGVs, as the main road vehicle types dominated the total traffic on the observed roads. The importance of these data is in the contribution of traffic activities in specific parts of the day to the overall residual noise. This contribution could not be shown in absolute values or shares since the inability to exclude or isolate the traffic component from the total port noise measured due to the continuity of this activity during the specific parts of the day. The same applies to port-related services and other actions performed in the examined area.

Following the setting and validation of the fundamental variables considered, primarily for their effect on the final results,

Table 7. Sound pressure level (L_Aeq) representing the total residual noise of the two examined areas according to the day, night, and evening levels.

Ship Type	Cargo Handled	Residual NoISE [dBA]
		Day (Lday)		Evening (Levening)		Night (Lnight)
		S *	NW *	S *	NW *	S *	NW *
Oil/chemical tanker	Bitumen	56.7	56.8	52.7	53.4	/	/
Bulk carrier	Bulk slag	53.5	51.3	50.1	48.7	49.1	48.0
Bulk carrier	Calcium	52.6	50.1	50.9	50.2	47.3	43.9
General cargo	Copper concentrate	50.8	52.1	49.6	47.5	46.6	44.5
Bulk carrier	Bulk slag	49.1	52.1	48.2	47.3	47.5	46.5
General cargo/MPV	Yacht	46.5	45.8	46.0	44.1	/	/
Bulk carrier	Scrap metal	54.1	54.7	50.7	49.3	/	/

* S—southern residential area (Brda district); NW—northwestern residential area (Vranjic district); in grey: values exceeded the threshold levels.

provides the output of the measurements conducted to determine the port noise levels. As indicated, these measurements were applied to two residential areas surrounding the cargo terminal in Split, showing the A-weighted continuous sound pressure levels (L_Aeq) and representing the total residual noise. The authors calculated the average values of residual noise based on the three day samples, two evening samples, and one night sample, with a duration of each measurement sample of one hour, individually for the day (L_day), evening (L_evening), and night (L_night) periods.

As a supplementary feature of the measurement aiming to determine the noise levels of working processes from ship and cargo operations in the port, the authors measured the sound pressure levels from dominant port noise sources. These were related to auxiliary engines, ventilation openings, and various operational statuses of cargo-handling equipment (quay cranes and conveyors). As for the impact of other traffic, industrial, and logistic activities in the port area, combined with the inability to determine the contribution of individual port noise sources to total residual noise, the authors examined the sound pressure level of this sample solely for night levels (L_night). This was performed for the lower intensity of the overall activities registered during the night period. The applied metrics enabled us to provide assumptions on the sound pressure level of the individual port noise sources related to the diverse status of working processes realized in the port. The values indicated in

Table 8. Maximum A-weighted noise level with fast time weighting during the measurement period (L_AFmax) of the diverse status of working processes realized in port during the night period (L_night).

Cargo Handled	Crane—Stand BY		Crane IN Operation—Slewing		Crane—Horizontal Load Movements		Operations—Two Cranes		Operations—Conveyors		AE and VO
	S *	NW *	S *	NW *	S *	NW *	S *	NW *	S *	NW *	S *	NW *
LAFmax [dBA]	47.4	45.8	49.5	47.2	52.5	49.4	53.5	50.4	48.3	47.6	53.6	54.5

* S—southern residential area (Brda district); NW—northwestern residential area (Vranjic district).

show the output of the selected period of cargo-handling equipment in operation, having a minor time sequence contribution compared to the total port and residual noise. In the context of sound level measurements, these noise levels can be characterized as the maximum level with A frequency weighting and fast time weighting during the measurement period (L_AFmax). Furthermore, the characteristics of the work processes were not continuous but impulsive, with repetitions during the cargo handling.

The final results represent the average values of three night samples of a ship positioned at the border of Berths 4 and 5 (Scenario 3). Table 8 provides the results of these measurements.

4.2. The Effects of Mitigation Actions on the Noise Levels in the Port

Based on the set objectives and considering the research findings generated from all the previous activities, which indicated the exceedance of the noise threshold values during night hours, the authors conducted the A-weighted sound pressure level measurement (L_Aeq) of an open working process in specific conditions during the night (L_night). This referred only to Scenario 3, considering the calcium cargo loading of a ship berthed at the border of Berths 4 and 5. This campaign included two separate measurement actions. The first involved the setting of an acoustic cover or enclosures on the existing cargo-handling equipment (mobile quay cranes). The second method considered the repositioning of the conveyor system for handling bulk cargo inside the warehouse during the loading procedures. The idea was to annulate the noise propagation from the port-related noise source in open space, while the extendable feature of a conveyor system having a telescopic slide ensured the direct loading of cargo to the ship holds, preventing the disruption of a determined loading rate. These adjustments were applied as an obligation to adopt the current regulations based on the noise limit levels while performing cargo-handling operations during night hours. The results generated from the previous research phases stimulated the modification of the operative and technical features of a working process from a terminal operator standpoint. Due to the previously emphasized situational features, it should be noted that the impact of exogenous effects was limited, primarily for the lower sound pressure level of other noise sources in the surrounding area. The results of the two separate measurement conditions are provided in

Table 9. The A-weighted sound pressure level measurement (L_Aeq) of an open working process in two specific conditions during night hours (L_night)—adjustment of technical and operational features.

Scenario 3	Mobile Quay Cranes–Enclosure Implementation		Conveyor Belt System–Respositioned in a Warehouse
	S *	NW *	S *	NW *
LAeq [dBA]	46.6	43.5	43.7	42.3

* S—southern residential area (Brda district); NW—northwestern residential area (Vranjic district).

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5. Discussion

This study represents the third and final part of a comprehensive study of noise measurement in the Split cargo port, so the authors will necessarily refer to the results of already published parts of the research. The goal was to assess the validity of citizens’ complaints about exceeding the intensity of noise from the cargo terminals, examine the noise sources and possibilities of noise reduction, and ultimately contribute to the sustainable development of the port near the residential area.

5.1. Interpretation of the Research Results

According to the set criteria, the results of the measurement campaign indicate complexity in determining the contribution of the noise emitted from the working processes in the port area to the total residual noise during loading and unloading operations and other related activities around the ships at berth. Primarily, these are the effects of different ports, traffic, industrial, and logistical sources, as well as other noise sources in the examined area, which vary due to the intensity of operations provided and the time of day realized. These specifics conditioned the modeling of the applied concept in this study, which included four connected measurement segments as previously elaborated. As the main objective of this study was to perform the measurements of sound pressure levels at the receivers’ position for the day (L_day), evening (L_evening), and night (L_night) levels of noise emitted from cargo terminals (cargo and other port-related operations), the research results pointed to the exceedance of the threshold values (Table 7) for the port noise mainly emitted during night (L_night) periods. This observation can be applied to both examined locations measured at the intersection of the industrial and residential zones. These results are in accordance with the residents’ perceptions of the portion of the excessive port noise in total residual noise emitted during night periods [18] that should be considered in applying efficient noise management strategies. Additionally, this statement can be highlighted as a crucial and most important research finding that emerged from the conducted measurement campaign. There are differences between noise characteristics and the sound-pressure levels of selected ships calling the port, revealing the continuous noise characteristics of a closed working process and impulsive noise characteristics of an open working process with high variations. The influence of individual working processes is strongly affected by the geographical settings of the measurements, traffic activities, operative protocols of the terminal operator, and various exogenous influences. These include the distance and height from the measuring location and assigned berthing spot of vessels calling the port, traffic density on the main roads surrounding the cargo terminal, working hours of cargo-handling activities, effects of the traffic-related noise sources in the port area (truck cargo transshipment) and background noise, meteorological and climate conditions, and various other impacts. Compared to the baseline conditions, the total residual noise of the examined scenarios shows significantly higher continuous sound pressure levels (L_Aeq) individually for all day–evening–night levels, but mainly within the values prescribed by the Ordinance. However, a residual sound-pressure level (L_Aeq) was found to exceed the threshold levels for night periods in all examined scenarios and for daily ones in Scenario 1. The port noise measurement in the case of berthed oil/chemical tankers carrying bitumen cargo (Scenario 1) was not performed at the border of the industrial and mixed, predominantly residential zone, which influenced the final results, increasing the calculated average sound pressure levels. The values of the noise pressure level at a close distance from the ship, as a primary source of noise emissions in port, have not been included in the final calculation. These data could be used when modeling and creating simulations of the noise propagation from the cargo terminal toward the inhabited area.

The authors intended to isolate the noise generated from the working processes in the port during cargo-handling operations. They found it applicable solely for night periods when the sound pressure level of other noise sources was significantly lower. These conditions enabled us to assess the noise emission contribution of the open and closed working processes as a part of the total residual noise. The noise emission of open working processes was found to be impulsive, which indicates that these values represent a sound-pressure level associated with handling the cargo (L_AFmax), opposite to the closed working process having a continuous noise characterization. Despite the small time frames of measured noise emissions in the working processes under different conditions (utilization of cranes, conveyors, or noise emissions from AE and VO), all these processes contributed, to some extent, to the exceedance of equivalent continuous sound levels measured during night periods. In addition, the noise emitted from auxiliary engines and ventilation openings of berthed ships during night periods was not considered in this part of the research, mainly because the closed working processes were not conducted at night. Finally, as for the requirement to fulfill the prescribed maximum permissible noise levels, which, according to the first research objective, was violated during night hours, the authors, in cooperation with terminal operators, measured the L_Aeq of an open working process during night hours (L_night) under two separate conditions. The first related to the setting of an acoustic cover on the mobile quay crane, and the second involved repositioning the conveyor system inside the warehouse while loading. The results of the noise emitted from the port in conditions of implemented acoustic covers on quay cranes indicated a decrease in L_Aeq for the two examined areas but without significant improvement. However, the change in the planning of cargo-handling operations, in which cargo was loaded via a conveyor system located inside the warehouse opposite the quay cranes, was very successful in terms of noise reduction strategies. These results, particularly the contributions to operational and technical modification of the cargo-handling process, could form the basis for adopting a general approach to reducing the impact of port noise based on the determined assumptions.

The wind certainly affects noise propagation, so the measuring instrument setup excludes the results at a wind speed greater than five m/s. It would be interesting to know how the wind speed of less than five m/s affected the results. In the noise measurement period, the wind directions were from the I, III, and IV quadrants. It is also usual in the summer months on the eastern Adriatic that the wind blows in the afternoon and evening from the sea and at night from the land. Depending on the exact measurement time, these variations were possible reasons for night noise exceedances in both residential zones located northwest and south of the port. This assumption needs further research.

5.2. Comparison of the Research Results with the Datasets Generated from the Previous Research

As this paper represents the final phase of the project NOIPOS [20], one of the objectives of this paper was to compare the research results generated in this work with datasets from previous activities. That primarily included the noise levels assessed by the local population living within the borders of the two districts in the vicinity of the port area [18] and the outcomes of simulations concerning the noise propagation of a ship at berth in predetermined conditions [22]. Additionally, this comparison includes the values of baseline conditions, thus total residual noise excluding the cargo-handling operations. For the purpose of this analysis, the noise levels of the two examined areas (districts included in the measurement process) and baseline conditions were consolidated and presented as averages to enable the comparison between datasets. The comparison of results generated by the provision of a measurement campaign and survey analyses of residents considering their perception of port noise emission values are indicated in

Table 10. Comparison of the three datasets considering the sound pressure levels of different actions.

Sound Pressure Level (LAeq) *	Day (Lday)	Evening (Levening)	Night (Lnight)
Baseline conditions–measurements	44.8 dB	42.5 dB	40.9 dB
Residual noise–measurements	51.9 dB	49.2 dB	46.7 dB
Residents’ perception–assessment	74 dB	62 dB	58 dB

* average values, applicable to both areas examined in this study.

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The validation of two databases indicates the strong influence of residents’ subjective perception on the noise emission originating from the area surrounding the residential zone concerning the residual noise-determined levels. The difference ratio for the day–evening–night values varies from 20% (L_evening and L_night) to 30% (L_day). The psychophysical and emotional perception, combined with the lack of formal knowledge of noise and acoustic fundamentals, certainly affected the assessment process, as indicated by Jelić Mrčelić et al. [18]. The contributions of these analytics should be used to initiate public events and external communications policies to increase the knowledge level on port noise. When comparing the sound pressure levels from the noise measurement with the results of conducted noise propagation simulations from a berthed ship in the Split Port, the results partially confirm the assumptions raised and indicated in simulations. That relates to both noise levels considered in simulations from a close distance and the results of noise propagation in cases when measured directly from the noise sources (ship funnel). As the simulations of noise propagation aimed to determine the affected area of noise emission from the predetermined sources, thus the maximum radius of propagation according to the set criterion level of 55 dB, the results of the measured residual noise partially confirm the simulation results of noise levels considered from the close distance (40 m). Only for this research segment in the paper did the authors measure the samples of a sound-pressure level at a close distance (40 m) from the primary source of noise (ship) emissions. These results were not considered from the primary research objective standpoint, as the values were not representative in the context of the fundamental research subject and determined objectives. That relates to the measurement process of port noise emissions and its implications for the local population affected by the annoyance and other health-related issues generated by port noise. These samples were collected from forward, aft, and midship. The A-weighted continuous sound pressure levels (L_Aeq) measured from all the ships carrying different cargo at the 40 m distance varied in the range of 65–75 dB when all samples from the database were aggregated (including the individual day–evening–night values). It confirms the assumption drawn in the first paper [22], where the input data of sound level measured from a distance of 40 m and implemented in the simulation metrics was set to 70 dB. However, the correlation between the simulation results of the determined area affected by the noise emitted directly from the ship source (ships’ funnel) and research findings in this study (residual noise) require further analysis to draw relevant arguments. As the authors in Vukić et al. [22] assumed ideal conditions and hypothetical propositions of the terrain for noise propagation in open space, the results should be accepted with limitations. The future work should eliminate the methodological constraints when conducting the simulations by integrating the inputs generated by real-time measurements and specifics of the examined area.

5.3. Recommendations for Improving Noise Management and Application of Noise Mitigation Measures in the Port Area

Two significant conclusions emerge from the results of this research. One concerns the verification of the exceedance of the thresholds for the maximum permissible noise levels during the night hours, and the other is the need to develop efficient port noise mitigation strategies in order to reduce the adverse effects of noise on the residents living in the areas surrounding the port. The calculated values of residual noise emitted during the night validate the perception of the local population on excessive noise emissions, confirming the potential harmful noise effects from port and traffic activities on their general health status and living standards. The objective of this paper was to calculate the total residual noise, primarily for the inability to isolate port noise from the other related sources, mainly the noise generated from transport activities. This limitation certainly prevented the determination of the objective port noise contribution to the citizen’s concerns. Despite this argument, the obligation and responsibility of terminal operators to adopt noise management strategies is undeniable concerning the social responsibility of maritime ports. It is also a competitive factor among ports intending to reach sustainability by adopting the green port strategic principles. However, the ports, as crucial nodes in global supply chains, should be granted the special purpose entities status with specific regulations applied on the determined noise levels, which enable the efficient provision of port operations despite the location of their setting and working hours. The adoption of the operative modification in the loading process by using the conveyor system positioned inside the warehouse while loading resulted in a significant decrease in the overall port noise. These adjustments should be incorporated into general noise mitigation procedures of port and terminal operators according to the specifics of the port area in certain conditions. Considering the specifics of the measurement process, it should be emphasized that cargo-related operations were not constant during the measurement process, which points to the discontinuous characteristics of the residual noise emitted. These conditions of silence, periods in which all the noise sources were halted or absent, can be associated with the questions raised by Goh et al. [40] as to how the public perceives the silence and whether the silence can be accepted positively or merely judged and inferred. In the mentioned research, the empirical verification has shown “hearing the silence” as a positive attribute. These findings can be applied to the research findings generated in this study when examining the resident perception of noise emitted from various port-related sources, especially the unawareness of the discontinuous characteristics of the working process or periods of silence. If we analyze the time fragments of residual noise while performing cargo-handling operations of open working processes, the sound emitted while repositioning the mobile quay crane between cargo holds could be one aspect that increases the level of annoyance, stress, sleep disorder, loss of concentration, etc., particularly at night. That primarily applies to the Brda district (south of the cargo terminal) and can be resolved by engaging a crew of signalmen who could replace the light and sound indications when performing these actions. As for the specific features of scrap metal cargo, which significantly raise the total residual noise, the tendency should be to reduce the handling and transshipment operations during night hours. Generally, port management should strive to invest in green technologies to prevent excessive noise emissions from cargo terminals. This relates to the acquisition of cargo-handling equipment with lower emissions of sound pressure levels. In addition, other relevant actions should be considered, such as the greening of the environment, installing noise barriers, and planting trees and shrubs as noise buffers to prevent the port noise propagation toward the residential areas, especially those located on the southern part of the terminal (Brda district). Noise due to maneuvering procedures from large ships during docking can partially explain the acoustic scenario with greater penetration into the territory at the mooring areas within the industrial area (Berths 3–6). The terminal operator should consider improving the operative plan for berthing, cargo handling, and cargo trans-shipment in order to lower the noise emissions, primarily toward the Vranjic peninsula. It includes the berthing operations of vessels exclusively in the bottom of the semi-enclosed basin, repositioning the mobile quay cranes, performing cargo handling at Berth 5, and performing cargo transshipment while preventing the use of trucks. Additional commercial challenges of management concern the use of a conveyor system for loading purposes when repositioned inside the warehouse, with the aim of eliminating noise propagation in the inhabited areas. This is related to the challenge of maintaining the port’s overall competitiveness in terms of a relatively higher loading rate compared to the other ports in the area while, at the same time, being obliged to comply with the established noise emission limits in certain zones, according to defined time levels. Since noise levels under the above conditions, based on the measurements made during this study, were well below the levels prescribed by the Ordinance for inhabited areas during the night hours (the limit is 45 dB), the only approach to maintaining the work process during the night is to apply the proposed operational measures. However, since the terminal operator uses the conveyor system for only one-third of the total cargo loading (during the night), these conditions could jeopardize the commercial position of the port in the overall market, so proper management of these processes is required. The noise generated from traffic-related sources represents an additional challenge not thoroughly discussed in this research. Empirical research on the contribution of traffic activities to residual noise by setting the traffic counters and providing in-depth measurements should be considered in the future. Finally, as for the port–city interface, current urban planning has enabled the development of the two mutually diverse zones (industrial and residential) at a close distance. The city administration should consider applying appropriate mechanisms to expand the port-related activities in the area that had initially been designated as an industrial zone. This would enhance the competitiveness of a cargo port defined as a strategic resource for the future development of the whole region.

Despite the intention to evaluate the research objectives set, this study has several limitations. First, it relates to a small sample of analyzed scenarios, which includes the measurement of sound pressure of several ships calling at the cargo terminals in the Port of Split at different times of the day, according to the described methodology. In addition, several assumptions were made regarding the noise measurement and process, including the sound pressure measurement of the indicated work processes, the conclusions from previous work referring to the results of the simulation of noise propagation, the generally accepted dominant sources in the port and the characterization of the work process. In order to better present the research results, some values have been presented as averages, including the comparison of the results with those from previous studies. Finally, some of the micro-local and exogenous peculiarities were neglected in the model, such as the setting of the measurement process, which referred to the exclusion of meteorological conditions that could violate the objectivity of the results (wind, rain) and neglecting the influence of noise generated by the adjacent road. These peculiarities certainly influenced the established conclusions, so the future continuation of the research topic should aim to eliminate these limitations. The recommendations for the continuation of this research include the establishment of fully integrated measurement units that include the implementation of a permanent noise measurement station in both populated areas in combination with video surveillance, a meteorological station, traffic counters on the main roads around the populated area and other related instruments (anemometer) that should expand the research sample. This would allow researchers to analyze the behavior of noise emitted from port and traffic sources under different conditions. The creation of a noise map showing the propagation of noise in the port area is also recommended but was not applied in this study due to the insufficient data and tools required to create the model, as well as the need to maintain the data in the long term. It would also increase the representativeness and objectivity of the research results and the arguments formulated. However, the measurement of the individual noise sources in the area under investigation should finally clarify the question of their contribution to the overall residual noise in the port.

6. Conclusions

Noise pollution has always been a part of the sustainability concept and has been treated marginally until recently. Today, it presents one of the leading topics of sustainable development. Regulation is still deficient, especially in the maritime sector. Increasingly larger ships equipped with an increasing number of noise sources make living near the port less and less pleasant. This study focused on assessing the impact of port noise in Split, addressing the growing public concerns over the negative effects of port activities. This public pressure stems from the global increase in awareness of port noise in recent years. The research findings confirm the impact of the port on the examined areas; the maximum noise limits at night were exceeded in both residential areas under investigation. This is problematic from a regulatory standpoint and could result in citizens’ complaints as well as adverse health effects due to prolonged exposure without proper noise management. Referring to the survey of residents’ perception of the sound-pressure levels generated from various port-related activities determined in the previous research, this study validated and objectified the exceedance of noise levels during night hours, but to a far lesser extent than those stated by residents in the previous project activities. This also applies to the general levels of port noise perceived by the inhabitants, including the day and evening noise levels, which were considerably lower, according to this research. These contributions were found to be essential for the general knowledge of noise emission levels originating from ports and other related noise sources. Among the actions taken to mitigate noise pollution, this study demonstrates that implementing an effective loading procedure or selecting different handling equipment can significantly reduce overall noise levels in the port and inhabited surrounding areas. With the application of the set procedure, the terminal operator should fulfill the regulations prescribed on the maximum permissible noise levels in the inhabited zone. The results from this study can support decision-makers and establish operational standards during the planning phase of loading operations in ports for the implementation of port noise management and mitigation measures. All these procedures contribute to the port’s sustainability near residential areas.