We can measure LAeq and LAN of community noise correctly by short interval measurement, if frequency distributions of LpA are similar to that of by continuous measurement. We measured community noise for 24 hours at 6 sites, and for 1 month at 1 site. And we analyzed hour-by-hour changes and day-by-day changes of frequency distributions of LpA. Results of study on hour-by-hour changes of frequency distributions of LpA are as follows. In daytime, if traffic noises are mainly measured, we can get them correctly by measuring 30 minutes at most. But in nighttime, to get them correctly, we must measure continuously at nighttime, or measure 10 minutes interval every hour. Results of study on day-by-day changes of frequency distributions of LpA are as follows. In daytime, we can get them similar to that of by continuous measurement, in a month by 10 minutes interval measurement in a month. But in nighttime, noises propagate through long-distance, then noise levels depend on direction of wind changes day by day. And frequency distributions of LpA also change day by day. Therefore, it is appeared that we must measure community noise for long interval to get frequency distributions of LpA correctly.
The major objective of this investigation is to evaluate the effects of visual and auditory information on the impression of the sound environment in our daily life. Thirty kinds of sound environments (sounds and their visual images) classified into five groups were used as stimuli. Firstly, thirty kinds of sounds were presented to twenty subjects. Secondly, their visual images, i.e. using a video, were presented. Finally, the sounds and the visual images were presented at the same time. In all experiments, the subjects were asked to evaluate their impressions on Semantic Differential (SD) scale when the stimuli were presented. The results of the factor analysis showed that, in the case of the water group, visual information gave greater effects on the impression of the sound environment than auditory information. It was also found that, in the case of some sound environments of other groups, the effects of visual and auditory information made those impressions buffered.
The hitting sound of golf clubs with metal heads and of a club with a wood head were measured to investigate differences in their acoustic properties. Hitting was executed either by a swing machine or a human player. The results of analysis showed that the clubs with metal heads generated sounds around 100dB (LpA, Fmax). This level was 5-15dB higher than that of the club with a wood head. The sounds of the metal-head clubs had relatively larger power in the high-frequency region of 4kHz and above compared to the wood-head club, which increased the overall levels. It would be desirable to develop a metal head with pleasant sound qualities, keeping the sound level lower in order to minimize damage to hearing.