4.2.2. Evaluation of Soundscape Improvement for Ceramic Passive Amplifiers
In order to explore the effect of ceramic passive amplifiers for mobile phones on improving the indoor soundscape, the experimental scores of the 10 samples were taken as a set of data, and the scores of no speakers and the electronic speaker were used as two other sets of data. One-way analysis of variance (ANOVA) was performed.
Table 8 and
Table 9 show the differences in sound source perception. When white noise was played, all scores of the three groups for the sound environment were statistically significant (
p < 0.01). When the sound playing was a popular song, the scores of the three groups for the sound environment still showed significant differences in “mechanical voice” and “artificial voice” (
p < 0.01), while there was little difference in “natural sound” (
p > 0.05) because popular songs do not contain “natural sound”.
In the post hoc significant difference (LSD) test, the score of “no speakers” was significantly lower than those of all samples and the electronic speaker (p < 0.05), and the scores of “natural sound” were significantly higher than those of all samples and the electronic speaker when white noise was played (p < 0.01). According to the score conversion of sound source recognition, the higher the score of noise (“mechanical voice”, “artificial voice”), the lower the score of “natural sound” and the better the noise shielding effect. Therefore, all samples and the electronic speaker achieved the effect of shielding the open-plan studio from ambient noise. For “natural sound” (when white noise is played), the score of the electronic speaker was significantly higher than that of sample 1 (M = 1.37, SD = 0.62; p < 0.01), which proves that sample 1 was better at transmitting “natural sound”. There was no significant difference in scores between the electronic speaker and all samples in terms of “mechanical voice” and “artificial voice” when playing a popular song (p > 0.05).
Table 10 and
Table 11 show the results of assessing emotional perception. Whether white noise or a popular song was playing, all emotional scores of no speakers, the electronic speaker, and the 10 samples were statistically significant (
p < 0.05). The post hoc LSD test showed that the “no speakers” scored significantly lower on six positive emotions (
p < 0.05) and significantly higher on six negative emotions (
p < 0.05) than all of the samples and the electronic speaker. The emotional score evaluation can be interpreted as follows: higher scores for six positive emotions or lower scores for six negative emotions indicate a higher comfort level of the soundscape. Therefore, the samples and the electronic speaker playing sound guided participants’ positive emotional perception.
Similarly, after the post hoc LSD test, there was no significant difference in the score for “pleasant” emotion between the electronic speaker and all samples when white noise was played (p < 0.05), indicating that the effect of the 10 samples in terms of guiding participants to perceive “pleasant” was similar to that of the electronic speaker. In terms of the scores for “calm”, “free”, and “familiar” emotions, the emotional score of seven samples was significantly higher than that of the electronic speaker (p < 0.05). In other words, the emotional guidance effect of the electronic speaker was worse than that of the passive amplifier in these positive emotions. The score of six positive emotions for sample 1 was significantly higher (p < 0.05) and the score of six negative emotions was significantly lower (p < 0.05) than that of the electronic speaker. The mood-improving effect of sample 1 went beyond the electronic speaker. There was no significant difference between the scores of positive “relaxed” and “lively” emotions for the other samples and the electronic speaker (p > 0.05) or the scores of the six negative emotions (p > 0.05). When a popular song was played, there was no significant difference between the electronic speaker and all samples in terms of emotional scores (p > 0.05).
Figure 5 and
Figure 6 show the calculations of differences in mood scores between the participants’ experience with no speakers, the samples, and the electronic speaker. When white noise was played, the overall difference between all samples and no speakers and the electronic speaker was significant. When playing a popular song, the overall difference between the samples and the no speakers was significant, and between the samples and the electronic speaker was not significant. When white noise was played, all samples were better at inducing positive perceptions than the electronic speaker. When playing a popular song, there was still a gap between all samples and the positive emotional guidance of the electronic speaker.
When white noise was played, the difference between “calm”, “relaxed”, “dull”, and “monotone” moods between the samples and no speakers was prominent. This suggests that soundscapes created by the samples were most helpful in restoring “calm” and “relaxed” moods, and prevented people from falling into “dull” and “monotone” moods. When playing a popular song, the difference between the samples and no speakers was significant in terms of “lively”, “dull”, and “monotone” moods. The results further confirm that all samples were most helpful in alleviating “dull” and “monotone” emotions.
Table 12 shows the differences in soundscape quality scores of the open-plan studios under the three conditions, and all scores are statistically significant (
p < 0.01). In the post hoc LSD test, the soundscape quality scores of all samples and the electronic speaker were significantly higher than those of no speakers after playing white noise and a popular song (
p < 0.01). The use of the samples and the electronic speaker successfully enhanced the soundscape quality of the open-plan studio. In the LSD test, there was no significant difference between the soundscape quality scores of the electronic speaker and all samples when playing a popular song (
p > 0.05). When playing white noise, the soundscape quality scores of samples 1 and 2 were significantly higher than that of the electronic speaker (M = 4.00, SD = 0.53; M = 3.97, SD = 0.62;
p < 0.01), indicating that samples 1 and 2 were better able to improve the indoor soundscape when playing “natural sound” than the electronic speaker.
4.2.3. Evaluation of Soundscape Differences between Ceramic Passive Amplifiers
In order to compare the differences in soundscape evaluation among the 10 samples, the mood and soundscape quality data of all samples were integrated after playing white noise and a popular song.
Table 13 and
Table 14 show the differences in mood scores of the 10 samples through descriptive analysis. The emotional scores of samples 1 and 2 were the most prominent among all the samples, followed by samples 9 and 10. The mood score of sample 4 was the worst among all samples, followed by samples 3 and 7. In the post hoc LSD test, the scores of four positive emotions of sample 1 were significantly higher (
p < 0.05), and the scores of five negative emotions were significantly lower (
p < 0.05) than those of sample 4. The “lively” and “free” scores of sample 1 were significantly higher (
p < 0.05) and the “dull” and “monotone” scores were significantly lower (
p < 0.05) than those of sample 5. The four positive emotions of sample 2 were significantly higher (
p < 0.05) and the two negative emotions were significantly lower (
p < 0.05) than those of sample 4. The “energetic” and “comfortable” scores of sample 2 were significantly higher than those of sample 5 (
p < 0.05). In other words, the effect of mood improvement for samples 1 and 2 was more obvious compared to samples 4 and 5.
Table 15 shows the differences in soundscape quality assessment among the 10 samples. Sample 1 had the highest score, followed by samples 2 and 10. Sample 4 had the lowest score, followed by samples 3 and 7. In the LSD test, the soundscape score of sample 1 was significantly higher than those of samples 3 to 9 (
p < 0.05), and the score of sample 10 was significantly higher than those of samples 3 to 8 (
p < 0.05). Samples 1 and 10 had the best ability to improve the quality of the indoor soundscape, which is consistent with the objective acoustic performance of the two samples.
The influence of non-acoustic factors of the 10 samples on soundscape perception can be summarized from the interview process. Based on the subjective perception of respondents, emotional recovery was mentioned more frequently. Twelve interviewees clearly stated that they experience a “relaxed” feeling and entered a relatively “calm” state when white noise and a popular song were played with the 10 samples, and other sounds could be ignored. Fourteen respondents thought the sound transmitted by the samples was more ethereal than that of the electronic speaker. Three interviewees mentioned that the sound of the passive amplifier attracted attention and they could not concentrate on their thoughts to some extent.
From the perspective of sound effect, the amplification effect of samples 1 and 10 was easier to perceive, and eight interviewees thought that the reverberation effect created by sample 6 was the most obvious. The sound amplification effect of samples 4, 5, and 7 was evaluated by the respondents as being tedious. With regard to appearance, all respondents indicated that they were affected by the ceramic material and shape of the samples when evaluating the soundscape quality. Then, ten respondents clearly expressed a desire to touch the sample.
Table 16 shows a comparison of the appearance scores of the samples.
Among them, the appearance of sample 1 had the highest score. When experiencing sample 1, respondents reported a corresponding increase in soundscape quality, which partly supported hypothesis 1.2. The appearance scores of samples 2, 8, and 9 were relatively high, and the corresponding soundscape quality scores were also relatively high. The appearance score of sample 4 was not low, but due to its poor amplification effect, the corresponding soundscape quality evaluation was not significantly improved. Due to the low appearance score of sample 10, the corresponding soundscape quality evaluation did not significantly improve. This shows that the visual and auditory perception of the samples were mutually influential.
Combining the results of the objective acoustic experiment and the subjective perception experiment, the improvement effect of ceramic passive amplifiers for mobile phones on the indoor soundscape was verified. Therefore, hypothesis 1 was supported. The specific experimental results are as follows:
The sound amplification effect of 10 samples was more obvious at medium frequency (500–1600 Hz) and high frequency (above 2000 Hz), and there was little difference in the effect of the mobile phone alone at low frequency (below 500 Hz). Among the samples, the sound amplification effects of samples 1, 2, and 10 were the most notable.
The 10 samples could play natural sound or music at the appropriate frequency, which can achieve the effect of masking indoor noise.
The indoor soundscape created by the 10 samples could help people enter a more “pleasant” and “relaxed” state and improve the overall quality of the indoor soundscape. The samples were more effective at inducing positive emotions when playing natural sounds than when playing an electronic speaker. Among the samples, samples 1 and 2 had the most positive effect on mood. Samples 4 and 5 showed an insufficient effect on guiding people’s positive perceptions.
In terms of non-acoustic effects, the sound transmitted by the ceramic material had a more restorative effect on emotional perception compared to the electronic speakers. On the premise of ensuring good acoustic performance, the recognizable aesthetic appearance of passive amplifiers is also conducive to the formation of a positive indoor soundscape.