Yukio Inukai

Unpleasantness and acceptable limits of low frequency sound

Equal unpleasantness sound pressure levels of pure tones from 10 Hz to 500Hz were obtained by the method of adjustment in which subjects adjusted sound pressure levels equating to subjective degrees of unpleasantness on a 4–steps rating scale. In addition, the maximum acceptable sound pressure levels were measured at each frequency, assuming four types of situations, that is, a living room, a bedroom, an office and a factory. It was found that the acceptable limits were equivalent to very low levels of unpleasantness in some situations. The third order polynomial models of physical variables were well fitted to the subjective response data.

A Multidimensional Evaluation Method for the Psychological Effects of Pure Tones at Low and Infrasonic Frequencies

Subjective ratings of pure tones at low and infrasonic (3–40 Hz) were obtained on a set of semantic-differential-type scales and were analysed by factor analysis. From the results, it was concluded that there are three main factors in the human response to the stimulus sound, these are 1) sound pressure, 2) vibration, and 3) loudness. In order to predict the human responses from the physical variables of the sound stimuli, prediction equations were derived for each of the three factors. Also, equal sensation contours for the factors were obtained. From these results, a new evaluation method for the psychological effects is proposed, which considers the multidimensional aspects of human perception at loww and infrasonic frequencies.

An evaluation method of combined effects of infrasound and audible noise

A psychophysical experiment was conducted to investigate an evaluation method for the combined effects of infrasound and audible noise. In the experiment, subjective rating of 80 mixed noise stimuli were obtained from 15 subjects on 22 semantic-differential-type scales. The stimulus noise conditions were mixtures of one of eight pure tones at 5, 10, 20, and 40 Hz and one of eight 1/3 octave band noises with centre frequencies 63, 125, 250, and 500 Hz. The rating data were subjected to a principal component analysis and yielded two principal components, these were interpreted as the perceptual components of infrasound and audible noise respectively. On the basis of this result, a psychophysical model was proposed to make two-dimensional predictions of subjective ratings from the physical variables of the noise stimuli. Following this model, a best weighting curve, in combination with the A-weighting curve and their regression weights, were estimated. The results showed that the psychological model successfully described the rating data.

Case Studies of Field Measurements of Low Frequency Sound and Complaints by a Non Profit Organization for Supporting Noise, Vibration and Low Frequency Noise Complainants in Japan

The number of noise complaints of Japan is around 15,000 a year and there are about 200 complaints of low frequency noise. In our NPO (Non Profit Organization), the specialists as volunteers on noise, vibration and low frequency noise take counsel with the complaints and measure the low frequency noise. It is difficult to measure the noise in the night by local government, and in such cases we measure the noise in the night for a long-time in complainants house. However, sometimes we cannot find the appropriate level of low frequency noise, though the complainant appeals for the serious damage by low frequency noise. Therefore we measured the complaints reaction at the same time with low frequency noise in the complainants house. We analyzed the correlation between the complaints reaction and measured low frequency noise. In many cases, we cannot find out the correlation between the measured low frequency noise and complainants reaction.

Effect of Ageing on Hearing Thresholds in the Low Frequency Region

The hearing threshold for low frequency (LF) tones was measured in a pressure field to investigate the effects of ageing on hearing sensitivity. Participants were young adults around 20 years old and older adults over 60. Measurement results showed that the older listeners had a higher threshold, on average, than the young listeners. The difference of median thresholds between these two groups was about 10 dB at every measurement frequency. Furthermore, hearing abnormalities other than age-related hearing loss showed no great effect upon the LF thresholds. Comparison of LF thresholds and audiograms (i.e. mid and high frequency hearing) of the older listeners revealed only moderate correlation between them. These results suggest that older people retain good hearing sensitivity in the LF region, in contrast to their often-degraded sensitivity at higher frequencies. Therefore, in LF noise evaluation, we should carefully regard the possibility that older listeners can perceive a low level LF noise.

Psychological and physiological response of low frequency noise of ordinary persons and complainants

In Japan, there are some complainants of low frequency noise. There are two sorts of complains on low frequency noise. One complain is the phenomenon of rattling noise. Light windows or doors are vibrated and rattled by the pressure of low frequency noise. Sound sources are a big diesel engine, pass by of a heavy truck on a highway bridge, a gas turbine engine generator etc. The other complaints are the direct hearing or detection of low frequency noise. Sound sources are a boiler, a cooling tower, etc., near neighbors, or solid borne noise inside a room. But recently, there are some complains at very low level and the sound source cannot be detected. In these cases, there may be much influences by mass media and Internet knowledge. In this paper we explain the mechanism of complains on low frequency noise as bellows. Hearing thresholds of ordinary persons and complainants. Physiological response of ordinary persons and complainants. Time history of annoyance of complainants according to on-and-off of sou...

Hearing Thresholds for Low-Frequency Complex Tones of Less Than 150 Hz

Hearing thresholds for low-frequency complex tones were measured to investigate effects of intensity and frequency differences between components and effects of the number of components on the detection of complexes. Complex tones comprised two tones, geometrically centered at 60 Hz, with frequency differences of 30, 60, 90, or 120 Hz. Sound pressure levels of the two tones were set to equal intensity or to equal sensation level. Additional threshold measurements were conducted for complex tones comprising 2–6 components at 25–145 Hz. A complex signal with multiple tones was detectable even if the levels of individual components were below the threshold. The improvement of complex signal detection varied greatly with the level difference and number of tones. Threshold levels for complex tones (in terms of level per component) decreased as the number of tones increased. Complex tones whose components have mutually similar frequencies were more detectable than those with separated components.

Analysis of psychological effects of low‐frequency noise using structural covariance models

It is necessary to discuss comprehensively effects of low‐frequency noise (LFN) on different kinds of modalities by extracting multidimensional bases of evaluation in order to clarify the characteristics of human sensation for LFN, because humans have no sense organ singularly specialized for LFN. In previous research, it was confirmed that there were three main factors of psychological evaluation of LFN by the method of factor analysis: loudness, oppression, and vibration. The purpose is to formulate the relation between physical stimuli and psychological evaluation for LFN by introducing structural relationships and using a multivariate technique to access causations and correlations. The method uses psychophysical experiments and statistical analysis. Pure sine‐wave stimuli in 22 conditions were radiated with a frequency from 3 to 40 Hz, and sound‐pressure level from 70 to 125 dB. Subjects evaluated the stimuli for the 22 psychological indices by psychophysical methods. Structures among the physical st...