Measurements of personal noise exposure in daily life are made for 142 workers in Nagoya. At the same time the subjects are required to reply several questions concerning sound environments of their workshops, commuting hours, in and around their residences. The questions are "How do you think about noise in each place -X_1:loud, X_2:medium, and X_3:low?" and "What opinion do you have for the noise -Y_1:should be abated, Y_2:to be reduced but difficult, and Y_3:pay no attention?". The subjects are classified by means of responses X_i(i=1, 2, 3)and Y_j(j=1, 2, 3) and their cross X_iY_j. Average L_<eq> is calculated for each class of responses and found to be reasonable correspondence between its value and the rank of responses. Ratios of responses X_i(i=1, 2, 3) and those of responses Y_j(j=1, 2, 3) against L_<eq> are also investigated. Response characteristics to each sound environment are discussed. Response of workers to noises during commuting hours and around residence are severe comparing with those to noises in workshop and in residence.
Usually ultrasonic transducers can only radiate ultrasonic waves of a narrow bandwidth, but it is possible to make a broad bandwidth by making a wedged type. The wedged transducers are made of PZT having the thickness extensional vibration. The fundamental characteristics of them are investigated, and the applications using them are attempted. First, the frequency characteristics of the free impedance and of the phase of the wedged transducers are measured. Also, the radiation patterns are observed using the schlieren method. Next, as the applications using those transducers two experiments are attempted. The one is the ultrasonic radiation of a broad bandwidth toward one direction using the semicylindrical wedged transducer. The other is the ultrasonic thickness measurement with resonance technique using the plate wedgrd and semicylindrical wedged transducer.
In this paper, a method of predicting the diffracted sound field behind the respective infinite plane screens with slits or a rectangular aperture is described. Macdonald's formula for a thin barrier and Pierce's formula for the doubled-edge diffraction by a thick three-sided barrier are used in this study, and this procedure for a rectangular aperture primarily follows Fresnel-Kirchhoff's diffraction theory. The calculated results for several kinds of small-scale model, obtained by the present procedure, are compared with experimental results.
According to the acoustical method adopted herewith, the 2kHz pure tone that travels with a duration of 20msec followed by the tone of the same frequency is given as the acoustical stimulus and the time interval between the two is adjusted in such a way as to bring about psychological fusion of the two tones, each subject being asked to give his differential threshold value τ_m. In the same way, the subject's differential threshold value φ_m of the flicker fusion technique is also obtained. Data based on 7 subjects. The analysis of the relation between the degree of fatigue and τ_m and φ_m indicates that τ_m and φ_m are both related to the degree of fatigue and that the τ_m and the φ_m stand almost in the reverse relation to each other as to the fatigue degree. Factors that contribute to τ_m or φ_m are analyzed and the degree of their contribution is determined by the Quantification Theory I. τ_m and φ_m have generally negative correlation coefficients to each other, but as to the fatigue state, they stand to each other in positive relations. The average τ_m per day of the week and the frequency of incidence of fatigue per day of the week (F_p) stand in correlational relations to each other, but the correlation coefficients of τ_m are greater for young adolescents while those of φ_m tend to be greater for elder people.
The application of L_<eq> as a measure of loudness of various noises is investigated. Nine kinds of noise sources, -aircraft noise, super express train noise, train noise, road traffic noise, speech, music, impulsive noise, artificial level-fluctuating noise and steady noise -are used as stimuli. The duration is about 10 sec except impulsive noise. Four kind levels are used in each noise source, therefore 36 stimuli are contained in a stimulus series. They are presented in random order and their loudness are judged by magnitude estimation. As a result of experiment, it is found that L_<eq> can be used as a good measure of the loudness of various noise as a first approximation. Strictly speaking, however, there is a slight, but systematical deviation from L_<eq> in PSE's of some noise sources. This fact suggests that it is necessary to add some factors to L_<eq> in order to decide the permissible levels of these noise sources.