Acoustics Research Unit
Psychoacoustics concerns the study of psychological and physiological responses associated with sound.
Auditory experiments have been carried out to investigate the relationship between different level indices and subjective responses to impact sounds from floors . Measurements of impact sounds generated by the ISO rubber ball (heavy/soft impact source) were conducted in apartment buildings with box-frame type reinforced concrete structures. Variations in frequency characteristics were found in the ISO rubber ball sounds and these were classified into three frequency groups. Sound quality ratings (LLz and Nmax) and instrumental metrics (LAeq, LAmax and Lm,1/1(63−500)) showed good correlation with impact sound annoyance. Among them, LAmax was proposed as a practical descriptor of the auditory sensation of ISO rubber ball sounds on the basis of measurement and calculation procedures. Additional auditory experiments were conducted to characterize the classified impact sound groups and to evaluate the annoyance of ISO rubber ball sounds through paired comparison and semantic differential tests. Results show that the ISO rubber ball sound with a dominant sound pressure level at 250 Hz was most annoying. Sound Quality metrics were used to explain the annoyance level of heavy-weight floor impact sounds. The annoyance obtained from the paired comparison test correlated well with loudness and fluctuation strength. In the semantic differential test, it was found that the adjectives describing loudness had a dominant effect on the subjects’ annoyance levels.
Subjective evaluation of impact sounds from heavyweight floors has also been carried out 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 (ISO rubber ball) in real apartments, so that impact sound pressure levels in terms of LAmax and IACC could be analyzed. Just noticeable differences (JND) of impact SPL and IACC were investigated through the use of the ISO rubber ball. 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 ISO rubber ball sounds can be improved by controlling IACC, as well as impact SPL.
The combined 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 20Hz 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.
A study has been carried out to assess the effects of different noise combinations on sleep with a single noise source and with combined noise sources . Road traffic noise and construction or movie noise combined with road traffic noise were used as the single noise source and the combined noise sources, respectively. When the sound pressure level of road traffic noise was kept constant, levels of the construction and movie noise were changed. Twenty participants were followed for approximately two weeks, during which their sleep was evaluated using a questionnaire, including questions on sleeping behaviour, premature awakening, and subjective responses. The results showed that the combined noise sources including construction noise decreased the number of participants who fell asleep within an hour and increased the number that were awakened prematurely compared to the effects of road traffic noise combined with movie noise. However, similar tendencies were observed while evaluating sleep quality, sleep disturbance, and annoyance.
Overall dissatisfaction from multiple noise sources in residential buildings has been assessed . A quantification model was constructed in two steps; a survey and an auditory experiment. The relation between dissatisfaction with the indoor noise environment and dissatisfaction with individual noises such as ﬂoor impact, airborne, drainage, and trafﬁc noises was found in the survey. Annoyance from individual noises was obtained as a function of the noise level from the laboratory experiment. Then, annoyance ratings were translated into the percentage of dissatisfaction based on the relation between annoyance and dissatisfaction obtained from the survey. Finally, equations were derived for predicting the degree of dissatisfaction with the overall indoor noise environment using individual noise levels, and a classiﬁcation method for the noise environment with multiple noise sources were proposed. The procedure and the quantiﬁcation model can be used for the assessment of the associated overall dissatisfaction of the indoor noise environment on the basis of the level of individual sources.
The influences of combined noise sources consisting of road traffic noise and construction noise on sleep disturbance have been investigated while the signal-to-noise ratio varied . Experiments were performed in the participants’ bedroom and sleep disturbance was evaluated using a questionnaire. The results showed that the number of awakenings increased when sound pressure level of construction noise was 10dB larger than that of road traffic noise.
Floor vibrations induced by humans walking barefoot were investigated in heavyweight buildings . In the first test, subjects were asked to walk across a floor and then rate the intensity of the vibrations, and the acceptability and serviceability of the floors. In the second test, subjects were seated on a chair in the middle of the floor and asked to rate the floor vibrations when a walker passed by the subjects. Floor vibrations induced by human walking were analysed using peak acceleration, root-mean-square (r.m.s.) acceleration, and the vibration dose value (VDV), with four frequency weighting functions (Wb, Wk, Wg, and Wm). Significant differences in the measured floor vibrations were found across the floor structures with greater floor vibration leading to greater perceived vibration intensity, lower acceptability, and lower serviceability. The VDV was correlated with perceptions of floor vibration when used with all four frequency weighting functions.
In-depth interviews  were conducted to understand how apartment building residents perceive and react to floor impact noise from upstairs. It was found that floor impact noise had diverse sources, with the majority originating from footsteps. The participants negatively perceived the noise as annoying and disturbing, and sleep disturbance was reported the most frequently. Cognitive and avoidant coping strategies were initially adopted, and complaints were only thereafter registered if the noise persisted. It was also observed that exposure to the noise led to self-reported health problems and concerns. The developed conceptual model highlights potential intervention measures for controlling noise perception and reactions to floor impact noise.
Questionnaire surveys  were carried out to provide an understanding of how residents in apartment buildings perceive and react to impact sounds coming from their upstairs neighbours’ dwellings. The conceptual model was tested using structural equation modelling with survey data from residents living in apartment buildings (N = 487). The results indicated that annoyance induced by floor impact noise was associated with perceived disturbance, coping, and self-reported health complaints. Noise sensitivity had a direct impact on perceived disturbance and an indirect impact on annoyance, and moderating variables affected the non-acoustic factors. Exposure to footstep noises increased the impact size of noise sensitivity to disturbance. In addition, a negative attitude towards neighbours (i.e., the noise source) moderated the positive relationship between annoyance and coping.
Another questionnaire survey  was performed 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. 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 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.
 Lee PJ, Kim JH, Jeon JY (2009) Psychoacoustical characteristics of impact ball sounds on concrete floors. Acta Acustica united with Acustica vol 95 pp 707-717.
 Jeon JY, Lee PJ, Kim JH, Yoo SY (2009) Subjective evaluation of heavy-weight floor impact sounds in relation to spatial characteristics. Journal of the Acoustical Society of America vol 125 pp 2987-2994.
 Lee PJ and Griffin MJ (2013) Combined effect of noise and vibration produced by high-speed trains on annoyance in buildings. Journal of the Acoustical Society of America vol 133 pp 2126-2135.
 Lee PJ, Shim MH, Jeon JY (2010) Effects of different noise combinations on sleep, as assessed
by a general questionnaire. Applied Acoustics vol 71 pp 870-875.
 Jeon JY, Ryu JK, Lee PJ (2010) A quantiﬁcation model of overall dissatisfaction with indoor noise environment in residential buildings. Applied Acoustics vol 71 pp 914-921.
 Lee PJ, Shim MH, Jeon JY (2009) Effect of type and S/N ratio of combined noise sources on sleep disturbance. Transactions of the Korean Society of Noise and Vibration Engineering vol 19 pp 960-966.
 Lee PJ, Lee BK, Griffin M (2015) Evaluation of floor vibrations induced by walking barefoot in heavyweight buildings Acta Acustica united with Acustica vol 101 pp 1199-1210.
 Park SH, Lee PJ, Yang KS (2016) Perception and reaction to floor impact noise in apartment buildings: A qualitative approach, Acta Acustica united with Acustica vol 102 pp 902-911.
 Park SH, Lee PJ, Yang KS, KW Kim (2016) Relationships between non-acoustic factors and subjective reactions to floor impact noise in apartment buildings, Journal of the Acoustical Society of America vol 139 pp 1158–1167.
 Lee PJ, Lee BK, Jeon JY, Zhang M, Kang J (2016) Impact of noise on psychological well-being and health in open plan offices: A structural equation modeling approach, Ergonomics vol 59 pp 222-234.