Pyoung Jik Lee

Perceptual assessment of quality of urban soundscapes with combined noise sources and water sounds

In this study, urban soundscapes containing combined noise sources were evaluated through field surveys and laboratory experiments. The effect of water sounds on masking urban noises was then examined in order to enhance the soundscape perception. Field surveys in 16 urban spaces were conducted through soundwalking to evaluate the annoyance of combined noise sources. Synthesis curves were derived for the relationships between noise levels and the percentage of highly annoyed (%HA) and the percentage of annoyed (%A) for the combined noise sources. Qualitative analysis was also made using semantic scales for evaluating the quality of the soundscape, and it was shown that the perception of acoustic comfort and loudness was strongly related to the annoyance. A laboratory auditory experiment was then conducted in order to quantify the total annoyance caused by road traffic noise and four types of construction noise. It was shown that the annoyance ratings were related to the types of construction noise in combination with road traffic noise and the level of the road traffic noise. Finally, water sounds were determined to be the best sounds to use for enhancing the urban soundscape. The level of the water sounds should be similar to or not less than 3 dB below the level of the urban noises.

Non-auditory factors affecting urban soundscape evaluation

The aim of this study is to characterize urban spaces, which combine landscape, acoustics, and lighting, and to investigate peoples perceptions of urban soundscapes through quantitative and qualitative analyses. A general questionnaire survey and soundwalk were performed to investigate soundscape perception in urban spaces. Non-auditory factors (visual image, day lighting, and olfactory perceptions), as well as acoustic comfort, were selected as the main contexts that affect soundscape perception, and context preferences and overall impressions were evaluated using an 11-point numerical scale. For qualitative analysis, a semantic differential test was performed in the form of a social survey, and subjects were also asked to describe their impressions during a soundwalk. The results showed that urban soundscapes can be characterized by soundmarks, and soundscape perceptions are dominated by acoustic comfort, visual images, and day lighting, whereas reverberance in urban spaces does not yield consistent preference judgments. It is posited that the subjective evaluation of reverberance can be replaced by physical measurements. The categories extracted from the qualitative analysis revealed that spatial impressions such as openness and density emerged as some of the contexts of soundscape perception.

Evaluating water sounds to improve the soundscape of urban areas affected by traffic noise

The acoustic characteristics of various kinds of water sounds were investigated to evaluate their suitability for improving the soundscape with road traffic in urban spaces. Audio recordings were made in urban spaces with water features such as fountains, streams, water sculptures, or waterfalls. The temporal and spectral aspects of the sounds were clarified, and subjective evaluations were performed to find the proper level difference between water sounds and road traffic noise for making urban soundscape more subjectively pleasant. The results indicated that the perceptual difference of the water sound level was around 3 dB with noises from road traffic in the background. The water sound, which had 3 dB less sound pressure level, was evaluated as preferable when the levels of road traffic noise were 55 or 75 dBA. It was also found that water sounds with relatively greater energy in low-frequency ranges were effective for masking noise caused by road traffic. The results of the present study will be valuable to urban designers and planners by providing guidelines for improving design solutions for water features in urban soundscape

Subjective evaluation of heavy-weight floor impact sounds in relation to spatial characteristics

This study investigated the effect of a spatial factor, the magnitude of interaural cross-correlation (IACC) function, on subjective responses to heavy-weight floor impact sounds. Heavy-weight impact sounds were generated by a heavy/soft impact source (impact ball) in real apartments, so that impact sound pressure levels (SPLs) (L(Amax)) and IACC could be analyzed. Just noticeable differences (JNDs) of impact SPL and IACC were investigated through the use of impact ball sounds. JNDs were determined by the criteria of 75% correct answers by participants, and it was found that JNDs of impact SPL and IACC were around 1.5 dB and 0.12-0.13, respectively. In addition, the annoyance caused by an impact ball was evaluated by changes in these two parameters. The results show that annoyance increased with increasing impact SPL and with decreasing IACC; the contributions of the two parameters to the scale value of annoyance were 79.3% and 20.4%, respectively. This indicates that the effects of IACC should be considered for the evaluation of annoyance, and the subjective response to impact ball sounds can be improved by controlling IACC, as well as impact SPL.

Use of the standard rubber ball as an impact source with heavyweight concrete floors

To select an appropriate standard floor impact source to simulate real floor impacts, objective and subjective evaluations of the floor impact sounds were conducted in a box-frame-type structure with reinforced concrete slab floors. The sounds simulated in the test were those that would result from an adult walking barefoot, children running and jumping (represented by a heavy-weight impact source, such as a bang machine or an impact ball), as well as those of a person walking in high-heels or a lightweight object being dropped (represented by a tapping machine). Similarity tests between human-made impact sounds and standard heavy-weight impact sounds were performed. Sound quality (SQ) metrics were used to predict the results of the similarity tests. These results showed that the impact sound of an impact ball is more similar to a human-made impact sound than the sound of a bang machine. A multiple regression analysis showed that loudness and roughness are significant factors describing the results of similarity judgment among SQ metrics. Much of the data from the standard impact sources, measured in reinforced concrete floors with rigid floor coverings, have been collected. An empirical relationship was established to convert the impact pressure sound level from the bang machine or tapping machine to that from the impact ball. This study indicates that the use of an impact ball is reliable for simulating human impact sounds.

Combined effect of noise and vibration produced by high-speed trains on annoyance in buildings

The effects of noise and vibration on annoyance in buildings during the passage of a nearby high-speed train have been investigated in a laboratory experiment with recorded train noise and 20 Hz vibration. The noises included the effects of two types of façade: windows-open and windows-closed. Subjects were exposed to six levels of noise and six magnitudes of vibration, and asked to rate annoyance using an 11-point numerical scale. The experiment consisted of four sessions: (1) evaluation of noise annoyance in the absence of vibration, (2) evaluation of total annoyance from simultaneous noise and vibration, (3) evaluation of noise annoyance in the presence of vibration, and (4) evaluation of vibration annoyance in the absence of noise. The results show that vibration did not influence ratings of noise annoyance, but that total annoyance caused by combined noise and vibration was considerably greater than the annoyance caused by noise alone. The noise annoyance and the total annoyance caused by combined noise and vibration were associated with subject self-ratings of noise sensitivity. Two classical models of total annoyance due to combined noise sources (maximum of the single source annoyance or the integration of individual annoyance ratings) provided useful predictions of the total annoyance caused by simultaneous noise and vibration.

Impact of noise on self-rated job satisfaction and health in open-plan offices: a structural equation modelling approach.

This study uses a structural equation model to examine the effects of noise on self-rated job satisfaction and health in open-plan offices. A total of 334 employees from six open-plan offices in China and Korea completed a questionnaire survey. The questionnaire included questions assessing noise disturbances and speech privacy, as well as job satisfaction and health. The results indicated that noise disturbance affected self-rated health. Contrary to popular expectation, the relationship between noise disturbance and job satisfaction was not significant. Rather, job satisfaction and satisfaction with the environment were negatively correlated with lack of speech privacy. Speech privacy was found to be affected by noise sensitivity, and longer noise exposure led to decreased job satisfaction. There was also evidence that speech privacy was a stronger predictor of satisfaction with environment and job satisfaction for participants with high noise sensitivity. In addition, fit models for employees from China and Korea showed slight differences. Practitioner Summary: This study is motivated by strong evidence that noise is the key source of complaints in open-plan offices. Survey results indicate that self-rated job satisfaction of workers in open-plan offices was negatively affected by lack of speech privacy and duration of disturbing noise.

Evaluation of speech transmission in open public spaces affected by combined noises.

In the present study, the effects of interference from combined noises on speech transmission were investigated in a simulated open public space. Sound fields for dominant noises were predicted using a typical urban square model surrounded by buildings. Then road traffic noise and two types of construction noises, corresponding to stationary and impulsive noises, were selected as background noises. Listening tests were performed on a group of adults, and the quality of speech transmission was evaluated using listening difficulty as well as intelligibility scores. During the listening tests, two factors that affect speech transmission performance were considered: (1) temporal characteristics of construction noise (stationary or impulsive) and (2) the levels of the construction and road traffic noises. The results indicated that word intelligibility scores and listening difficulty ratings were affected by the temporal characteristics of construction noise due to fluctuations in the background noise level. It was also observed that listening difficulty is unable to describe the speech transmission in noisy open public spaces showing larger variation than did word intelligibility scores.

Interior Noise Characteristics in Japanese, Korean and Chinese Subways

The aim of this study was to clarify the characteristics of interior noise in Japanese, Korean, and Chinese subways. The octave-band noise levels, A-weighted equivalent continuous sound pressure level (LAeq) and parameters extracted from interaural cross-correlation/autocorrelation functions (ACF/IACFs) were analyzed to evaluate the noise inside running train cars quantitatively and qualitatively. The average LAeq was 72-83 dBA. The IACF/ACF parameters of the noise showed variations in their values, suggesting they are affected by the characteristics of the trains running, wheel-rail interaction, and cross-section of the tunnels.

Measurement of Sound Field for Floor Impact Sounds Generated by Heavy/Soft Impact Sources

Field measurements of floor impact sounds at low frequencies give poor repeatability due to spatial sampling problems. In this study, the spatial distribution of heavy-weight impact sound pressure levels was investigated by field measurements using heavy/soft impact sources, which have been specified as a standard heavy-weight impact source in 140-11. The results of the present study showed that the vertical and horizontal distribution of measured sound pressure levels showed a significant room mode effect at low frequencies. Among the existing standards for measurement of a heavy-weight impact sound, KS F 2810-2 and JIS A 1440-2 provide an appropriate estimation of the room average sound pressure level for bare slab and floating floor, with respect to a low bias error and 95% confidence interval. The guideline for measurement of a heavy-weight impact source was recently proposed in order to complement the limitations of KS F 2810-2 and JIS A 1440-2, and it has been shown that the guideline appropriately performed in the test building and in living rooms of tested apartment buildings.