**1. Introduction**

Intensive port activity is sending an ever-growing amount of artificial underwater sound into the sea, mainly due to maritime traffic. This situation has been well documented for many years, especially by the world's navies [1]. Continuous underwater maritime transport noise has increased in recent decades [~3 dB per decade] [2]. In [3], recordings made in the 1960s were compared with others from the 1990s on the continental slope off Point South, California, showing how underwater noise related to maritime traffic has increased by up to 10 dB at frequencies of 20 to 300 Hz.

Underwater noise affects marine organisms in many ways [4], disrupts acoustic communications and auditory systems, alters behavior, and changes population distribution and abundance. Underwater noise generates physiological stress in marine organisms, stimulating nervous stress, increasing the metabolism, and reducing their immunity. These sounds affect not only aquatic mammals but also fish, amphibians, reptiles, and even invertebrates [5–7]. A study conducted in the Sado estuary in Setúbal, Portugal, one of the country's largest ports, revealed changes in the behavior of bottlenose dolphins. During daylight hours, they spent less time in areas with the highest underwater noise levels [8].

Given this information on the adverse effects of noise pollution, regulatory bodies increasingly require an assessment of the acoustic underwater noise in a marine habitat before a construction project. In a review of noise modeling processes in [9], the factors that affect underwater noise generation and basic aspects of environmental impact assessment (EIAs) are highlighted.

Human activities at sea generate different types of noise that vary in frequency and intensity and can be stationary and low frequency or impulsive and high intensity. The latter are produced in pile driving, underwater blasting, seismic exploration, or sounding activities, among others. Ports can also be subjected to impulsive noise due to activities such as pumping systems, air conditioning, civil engineering works in ports, and loading containers. In [10], recordings of underwater noises were made in the port of Fremantle Inner Harbor for several months. Subsequent analyses of these data detected underwater noise from various sources, these being vessel traffic, vehicles passing over a nearby bridge, machinery noise from regular operations in the port, and vibratory or impact pile driving recorded during during wharf construction.

Impulsive noises have adverse effects on marine life. In [11], which measured and modeled pile driving noise from a large number of points around Australia, an acoustic propagation model was proposed that allowed these results to be extrapolated to other locations. Another example, [12], on pile driving in the Ligurian Sea, found that fin whales (*Balaenoptera physalus*) avoided areas with impulsive noise. Another study, [13]. also analyzed whales' reactions to underwater impulsive noise; even 72 h after an airgun shooting period in the Alboran basin, fewer whale and received song levels were detected.

The aim of this study was to perform an acoustic characterization of impulsive underwater noise at the Port of Cartagena. This characterization was carried out according to the methodological criteria for the implementation of the Marine Strategy Framework Directive [14], including:


For this, a series of underwater acoustic measurements were taken in the bay, as described in Section 2.

### **2. Identification of Activities Potentially Generating Impulsive Noise in Port Facilities**

In accordance with the methodological guidelines published by the European Commission [15–17], the main sources of impulsive sound are


of this type include: multi-beam sonar with center frequency 15.5 kHz, sound pressure level (SPL): 237 dB re 1 μPa at 1 m (RMS) with omnidirectional beam; sub-bottom profiler with center frequency 3. 5 kHz, SPL: 204dB re: 1uPa at 1 m (RMS); or AN/SQS 56 sonar with center frequency of 6.8 kHz; 7.5 kHz; 8.2 kHz, SPL: 223 dB re 1 μP at 1 m (RMS) horizontal beam.


Some of these sources are regularly present in the port area, such as bathymetries and construction projects. In addition to the sources mentioned above, this study also considered the possibility of analyzing other routine activities, such as the loading and unloading of containers to analyze their potential impulsive noise production.
