Joo Young Hong

Designing sound and visual components for enhancement of urban soundscapes

The aim of this study is to investigate the effect of audio-visual components on environmental quality to improve soundscape. Natural sounds with road traffic noise and visual components in urban streets were evaluated through laboratory experiments. Waterfall and stream water sounds, as well as bird sounds, were selected to enhance the soundscape. Sixteen photomontages of a streetscape were constructed in combination with two types of water features and three types of vegetation which were chosen as positive visual components. The experiments consisted of audio-only, visual-only, and audio-visual conditions. The preferences and environmental qualities of the stimuli were evaluated by a numerical scale and 12 pairs of adjectives, respectively. The results showed that bird sounds were the most preferred among the natural sounds, while the sound of falling water was found to degrade the soundscape quality when the road traffic noise level was high. The visual effects of vegetation on aesthetic preference were significant, but those of water features relatively small. It was revealed that the perceptual dimensions of the environment were different from the noise levels. Particularly, the acoustic comfort factor related to soundscape quality considerably influenced preference for the overall environment at a higher level of road traffic noise.

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.

Soundscape evaluation in a Catholic cathedral and Buddhist temple precincts through social surveys and soundwalks

Religious precincts in urban spaces have their own religious spatiality formed by their sociocultural and historical background. It is necessary to identify the spatiality of urban religious precincts in their sociocultural contexts because soundscape perception is determined largely by context. In the present study, social surveys and soundwalks were performed in a Catholic cathedral and in Buddhist temple precincts in Seoul. In the surveys, important spatial functions, sound, and visual components of the Catholic cathedral and Buddhist temple precincts were investigated by principal component analysis. The results showed that the cathedral precincts play a more important role in social functions related to mainly visual components than the temple precincts do, whereas the functions for religious activities related to sound elements are more stressed in the temple precincts. In the soundwalk evaluation, contributions of soundscape and landscape components to tranquility in the two religious precincts were explored. It was found that pleasantness of soundscape and attractiveness of landscape significantly affected the perception of tranquility. In addition, it was revealed that a sense of enclosure could enhance tranquility in urban religious precincts.

A soundwalk study on the relationship between soundscape and overall quality of urban outdoor places

In a field study, we explored the relationship between the soundscape and the overall quality (good - bad) of outdoor open places. Thirty three residents in down town Stockholm participated in soundwalks near their homes. Along the soundwalk route, the participants assessed six places with respect to the soundscape, the visual environment and the overall quality of the place using a questionnaire. The six locations were preselected to vary in acoustic and visual quality. A regression model with pleasantness of the auditory and visual environment as predictors explained a substantial part of the variance in assessments of the six places overall quality. To disentangle the specific effects of auditory and visual aspects, the present study will be complemented with laboratory experiments in which visual and auditory aspects are independently manipulated.

Speech privacy and annoyance considerations in the acoustic environment of passenger cars of high-speed trains

It is necessary to consider not only annoyance of interior noises but also speech privacy to achieve acoustic comfort in a passenger car of a high-speed train because speech from other passengers can be annoying. This study aimed to explore an optimal acoustic environment to satisfy speech privacy and reduce annoyance in a passenger car. Two experiments were conducted using speech sources and compartment noise of a high speed train with varying speech-to-noise ratios (SNRA) and background noise levels (BNL). Speech intelligibility was tested in experiment I, and in experiment II, perceived speech privacy, annoyance, and acoustic comfort of combined sounds with speech and background noise were assessed. The results show that speech privacy and annoyance were significantly influenced by the SNRA. In particular, the acoustic comfort was evaluated as acceptable when the SNRA was less than -6 dB for both speech privacy and noise annoyance. In addition, annoyance increased significantly as the BNL exceeded 63 dBA, whereas the effect of the background-noise level on the speech privacy was not significant. These findings suggest that an optimal level of interior noise in a passenger car might exist between 59 and 63 dBA, taking normal speech levels into account.

Individual soundwalk methodology for assessment of urban soundscape.

This paper describes the individual soundwalk as a methodology for assessment of urban soundscapes. Compared with previous studies which have adopted soundwalk methodology, the individual soundwalk has significant differences in evaluation and analysis procedure. In the present study, soundwalks are performed individually, and subjects are asked to select the sites which produce a negative or positive impression while walking within a specific area. At each site, the subjects evaluate the soundscape perception using a questionnaire and describe why the urban soundscape is perceived favorably or unfavorably in terms of contexts. Furthermore, audio‐visual recordings are carried out and environmental factors such as day light, temperature, and humidity were measured simultaneously. From various responses of the subjects, the dominant contexts that influence the soundscape perception are derived, and design elements of urban spaces are extracted through qualitative analysis.

Noise in the passenger cars of high-speed trains

The aim of this study is to investigate the effects of both room acoustic conditions and spectral characteristics of noises on acoustic discomfort in a high-speed trains passenger car. Measurement of interior noises in a high-speed train was performed when the train was operating at speeds of 100 km/h and 300 km/h. Acoustic discomfort caused by interior noises was evaluated by paired comparison methods based on the variation of reverberation time (RT) in a passenger car and the spectral differences in interior noises. The effect of RT on acoustic discomfort was not significant, whereas acoustic discomfort significantly varied depending on spectral differences in noise. Acoustic discomfort increased with increment of the sound pressure level (SPL) ratio at high frequencies, and variation in high-frequency noise components were described using sharpness. Just noticeable differences of SPL with low- and high-frequency components were determined to be 3.7 and 2.9 dB, respectively. This indicates that subjects were more sensitive to differences in SPLs at the high-frequency range than differences at the low-frequency range. These results support that, for interior noises, reduction in SPLs at high frequencies would significantly contribute to improved acoustic quality in passenger cars of high-speed trains.

Monitoring floor impact sounds using detection algorithms in multi-story residential buildings

A monitoring and alarming system was designed to detect household noise occurrence in the multi-story residential buildings. This system is composed of a microphone combined with a home smart pad installed on a wall and a main server that can store data to discriminate household noise occurrence. Sound levels such as LAeq and LAmax were calculated in real time using developed digital signal processor (DSP) of the acoustical parameter analyzer in the home smart pad. A correction equation was applied based on the standard measurement method to provide accurate measurements. After measurement, the results were saved in the main server using Ethernet and inter-compared with the data of each household to discriminate the household noise occurrence. Finally, the alarm was raised depending on the decision criteria based on both the regulations of Korean government and subjective evaluation results from the previous study.

Laboratory experiments for speech intelligibility and speech privacy in passenger cars of high speed trains

This study explores the speech privacy criteria in passenger cars of high-speed trains. In-situ measurements were performed in running trains to analyze the acoustical characteristics of interior noises in train cabins, and laboratory experiments were conducted to determine the most appropriate single-number quantity for the assessment of speech privacy. In the listening tests, the participants were asked to rate (1) speech intelligibility, (2) speech privacy, and (3) annoyance with varying background noises and signal to noise ratio (SNR). From the results of the listening tests, the effects of background noise levels and SNR on the speech privacy and annoyance were examined and the optimum STI and background noise levels in the passenger car concerning both speech privacy and annoyance were derived.

Structural equation modeling of soundscape perception based on urban contexts

The aim of this study is to explore influential factors on urban soundscape perception. Objective and subjective assessments of the soundscapes in various urban spaces were conducted to characterize soundscape contexts using soundwalks. Evaluations were conducted at 21 locations, including residential, office, park, and commercial spaces in Seoul: the participants assessed their perceptions of both sound and landscape environments. In addition, laboratory experiments using audio-visual stimuli were carried out to validate the dominant soundscape factors derived from the soundwalks. From the results, a perception model of urban soundscapes consisting of physical and subjective indicators was suggested using structural equation modeling.