Kozo Hiramatsu

Investigations on road traffic noise based on an exponentially distributed vehicles model—single line flow of vehicles with same acoustic power

Statistical properties of road traffic noise have been investigated, based on a model in which point sources of the same acoustic power are distributed on an infinite line in such a way that the spacing between successive point sources has, as a probability density function, an exponential distribution. The basic parameters in the model are S and d , where S is the average spacing between successive vehicles and d is the perpendicular distance from an observation point to the line. The characteristic function, exp [ K(u) ], of sound intensity at an observation point was approximated by a function, exp [ K 1 ( u )], which depends on a parameter α[0≦α≦1] as well as on S and d . As a result, K 1 ( u ) was chosen so that K 1 ( u ) coincides with K(u) at d →0 and d →∞ and also I 1 coincides with I where I 1 and I are the means of the sound intensities determined by K 1 ( u ) and K(u) , respectively. From this approximate characteristic function, the probability density function (pdf), mean and variance of the sound pressure level (SPL) were derived. The value of α was determined as a function of d/S from the results of simulated calculations by means of a Monte Carlo method. The pdf, and the mean and the variance of the SPL thus obtained were in good agreement, respectively, with the histogram, the mean and the variance of the SPL obtained from simulated calculations. Comparisons are shown between the present results and those of previous investigators.

The development of Weinstein's noise sensitivity scale.

Many studies have shown the significant correlation between noise annoyance and noise sensitivity identified by Weinsteins noise sensitivity scale (WNS). However, the validity of the scale has not been sufficiently assessed. This study was designed to investigate the validity of each question in WNS and to develop a more valid noise sensitivity measurement scale. A questionnaire study was conducted in a residential area along trunk roads in Kusatsu, Japan, and 301 responses were collected. In this paper, noise sensitivity was defined as the factor that induced individual variability in reactions caused by noise exposure and that is not affected by the noise exposure. The relationship between noise exposure and answers to each question in WNS was investigated by multiple logistic regression analysis, and the influence of response bias on the score of WNS was examined. The results showed that WNS contained some questions that were inappropriately related to noise exposure level and that the score was affected by response bias. The reported correlation between annoyance and the score of WNS could be confounded by noise exposure and response bias. A noise sensitivity measurement scale named WNS-6B was newly developed, excluding the biased questions from the original WNS and applying binary coding to six-response options in order to reduce the response bias. WNS-6B seemed to be more appropriate to assess noise sensitivity than the original scale.

The effect of sound duration on annoyance

The purpose of this study is the investigation of the dependence of the duration effect on the level of noise and/or the duration itself, as well as the measurement of the duration effect expressed as a trading relation between the level and the duration. The stimulus was white noise whose duration ranged from 30 ms to 90 s for each of four levels of noise. Ten male and ten female subjects judged the annoyance of those sounds by means of the method of magnitude estimation. Results indicate that the annoyance increases in linear proportion to the duration up to 90 s in log-log co-ordinates. The slope of the duration effect is dependent on the level of sound and the result is most appropriately expressed by a multiple regression equation which contains an interaction term between the peak level and the duration. Contours for equal annoyance are drawn from the equation and the curves appear to show that the slope of the duration effect is dependent on the duration. This proves to be so, however, because of the dependence of the duration effect on the level of noise. If the interaction term between the peak level and the duration in the above equation is neglected, then the average slope of the duration effect can be obtained as 3·4 dB per doubling of the duration.

Experimental investigation on the effect of some temporal factors of nonsteady noise on annoyance

The effects of some temporal factors of nonsteady noise on annoyance was investigated by means of six experiments. The factors are rising speed, fluctuation speed, fluctuation frequency, and fluctuation deviation. The results show that the ratio of annoyance and the rising speed are in linear relation in log-log coordinates and the annoyance increase with the increase of rising speed from 25 to 1000 dB/s corresponds to the increase of sound pressure level of 2.6 dB. The fluctuation speed, the fluctuation frequency, and the fluctuation deviation have little effect on annoyance provided the equivalent sound level (Leq) is constant. The validity of some rating scales of fluctuating noise is discussed on the basis of the present experimental results.

Prediction of noise-induced temporary threshold shift

Abstract This paper reports the state of the art of the method for predicting TTS following exposure to noise having an arbitrary spectrum and temporal characteristics. Existence of the critical band for TTS was proved by two of the present authors from the results of their experiment. The center frequency and the width of the critical band were calculated, together with their 95% confidence limits. The theory of critical band enabled us to estimate TTS at a given test frequency due to noise having any spectrum content. In order to estimate the growth of TTS with the exposure time, new empirical formulae of TTS growth were determined based on the results obtained in the 8-h TTS experiments with exposure levels from 85 to 95 dB and those obtained in the 24-h TTS experiments with exposure levels from 65 to 86 dB. The formulae assume an asymptotic threshold shift and are expressed as a function of the exposure duration and the spectrum level of the exposure noise at the center frequency of critical band with respect to TTS . TTS due to steady state noise can be estimated by means of the critical band theory and the formulae of TTS growth. For the non-steady noise exposure, application of the method of unit step function is proved useful to estimate the TTS produced. The idea of the method is to approximate the temporal level change of the noise by a step function and then apply the formula of TTS growth to each of the steps where the level of noise is regarded as steady.

A rating scale experiment on loudness, noisiness and annoyance of environmental sounds

Abstract How people judge loudness, noisiness and annoyance of sounds was investigated by using a variety of environmental sounds. Fifty male and female subjects, aged from 18 to 60 years, heard 59 environmental sounds as well as seven kinds of white noise and judged their loudness, noisiness and annoyance on rating scales. Average scores on the three concepts given to the steady white noises are approximately in linear proportion to the level of the noise, with high correlation coefficients. The relationships were used to convert the scores given to the sounds to the levels of white noise which would have the same scores and can be regarded as points of subjective equality ( PSE s) of the sounds. It is found that the PSE thus obtained concerning loudness is best correlated among the three with Perceived Level and that concerning annoyance is least correlated with the level. Scattergrams of PSE s between the three concepts plotted against each other showed considerably high correlations. They are more correlated when sounds such as music, church bell, birds, etc., being on average judged pleasant or neutral, are excluded. This suggests that the human responses concerning those three concepts of auditory sensation and/or perception are mutually correlated. Lower correlation between loudness and annoyance, however, suggests sounds heard as equally loud could be differently annoying. More detailed analysis of the results showed that the judgement of loudness was not independent of noisiness and/or annoyance of the sound.

Mesurement of noise-evoked blood pressure by means of averaging method: Relation between blood pressure rise and SPL

Abstract Continuous measurement of systolic blood pressure is carried out while white noise is presented repeatedly to the subjects, and the signal output of the measurement device is stored in the computer. It has been found that the rise of systolic blood pressure owing to the sound presentation is clearly shown by the synchronized averaging of the signal. The present authors refer to this as noise-evoked blood pressure. The results of the experiments using white noise as the stimulus, with sound pressure levels (SPLs) from 60 to 100 dB, indicate that the evoked blood pressure reaches its peak at about 10 s after the onset of noise, and then gradually falls off. The blood pressure rise at the peak is proportional to the SPL and is 8·8 mmHg for the presentation of 100 dB white noise.

Temporal averaging of subjective magnitude and proposed rating scale for fluctuating noise

A method for predicting the effective sound level (ESL) is proposed in this paper. The effective sound level is the sound level of a steady noise which produces the same subjective magnitude as a fluctuating noise and may be measured as the point of subjective equality by means of psychometric methods. The proposed method gives the predicted value of ESL which is denoted as Leff, based on an assumption of integration and averaging of subjective magnitude. It has been shown that Leff can be expressed by an equation which contains the probability density function of the level distribution and two empirical parameters, the values of exponents for sound pressure and duration in the psychophysical function. The practical significance of the descriptor Leff was discussed in terms of the definition of the number of events. High correlation between Leff and the subjects’ response was found.

Socio‐cultural soundscape concepts to support policies for managing the acoustic environment

In the past half‐century, considerable effort has been invested in the academic, technological, and political arenas to achieve an adequate acoustic environment. Various national and international policy guidance documents have made reasonable progress in establishing a framework for a common approach to minimizing environmental noise, such as documents from various national Environmental Protection Agencies, the World Health Organization, and the European Union. Although these documents have provided useful information for global application, they only address minimizing the negative side of the acoustic environment (i.e., noise), they focus primarily on acoustics issues at the national or international level, and they still have not adequately considered implementation issues related to socio‐cultural differences. To deal with the practical problems that exist in the acoustic environment in the context of different cultures, continuing research and new policy guidance are needed to address different loc...

Soundscapegraphy of old‐town of Kyoto with the Gion Festival

The soundscape of the Yamahoko‐cho area in the old capital of Japan, Kyoto, is described from various aspects based on an intensive survey of acoustic ecology. The area located in the city center is famous for the Gion Festival, which is one of the biggest and oldest festivals in the country. The area’s soundscape on ordinary days is basically dominated by the noises of automobiles passing through the streets, since there are also companies and shops in the area, which is the trading center of Japanese costumes, kimono. In July, when the ceremony and festival are undertaken for 1 month, the soundscape changes to be dominated by a variety of sounds related to the festival. Particularly during the days when bands of music by flutes, drums, and small gongs are performed, the soundscape of the area becomes a complete festival one. The music is so famous that it is recognized as characteristic of the city. The residents in the area are raised listening to the sounds in summer, and these sounds are closely conn...