This paper is concerned with personal noise exposure of workers in daily life and their reactions to noise environments. In many cases L_<eq24> are decided by the noise exposure due to work and commutation, especially in the cases of skilled workers or ones whose L_<eq24> are high, their noise exposure due to work are usually most predominant. Next, analysis and prediction of L_<eq> during work and also during commutation are done using reaction to noise environments as well as the attitude of subjects. From this a method of prediction of L_<eq24> of workers is proposed and the results are compared with the measured ones. Finally subjects are classified by a series of reaction to the noise environment in workshop, on commutation, and at home. As the results, the subjects over 50% respond as "medium" or "low" to all noise environments. On the contrary, 25% and 20% of subjects respond as "loud" to noise in workshop and commutation, respectively. Partial order scalogram analysis (POSA) is also made which throws light on mental attitude of workers to noise environments in daily life
Every information on the statistical property of state variables for the actual system of environmental noise with various types of probability form, nonstationarity, nonlinearity and arbitrary correlation property can be derived by first finding the expression of the multivariate joint probability function of the state variables. In this paper, the generalized expression of joint probability function in the form of statistical orthogonal expansion series with the quantized or continuous levels can be derived in a suitable form to the actual situation on the variety of probability fluctuation and digital or analogue type level observations, especially by focussing our aim on the basic viewpoint. Finally, after once the legitimacy of the present theory is confirmed by means of digital simulation, the effectiveness of the generalized method is confirmed by applying it to experimentally observed road traffic noise data.
In this paper,an analytical technique for calculating the amplitude of reflected sound wave from a rigid concave disk is described. This theory is treated on the assumption that a receiver is located separately from a transmitter. The formulas for the reflectivity are derived approximately under certain geometrical restrictions. The reflectivity is termed as the "directional sound reflectivity, "which is defined as the ratio of the reflected sound pressure from a target to the calculated one which is derived from the theory of geometrical optics. Moreover, comparison with a radiated sound pressure from a concave source, the reflected sound pressure when a transmitter is located at a center of curvature is described. To verify the validity of the approach, some experiments were performed in air at the frequency of 39. 80kHz. Experimental results showed good agreement between the calculated and the measured values and this confirmed the usefulness of the present technique to calculate the reflection of sound waves from a concave disk.
Temporal masking of brief test-tone pulses by a 2-kHz sinusoidal masker burst is investigated using simultaneous,forward and backward masking paradigms. The time interval ΔT between masker and test-tone pulse and test-tone frequency are varied. The most important result is an atlas of temporal masking effects produced by the masker onset or offset. Masking patterns grow and spread abruptly at transients, that is, the masked thresholds at short time interval ΔT at onset or offset are considerably higher than the thresholds in steady-state conditions over wide ranges in frequency. Temporal masking patterns at masker onset are investigated with a basilar membrane model which shows similar effects to the patterns. Comparison of temporal masking pattern with instantaneous power spectra of a sinusoidal masker burst shows that the masking pattern can not be directly estimated by physical characteristics of the input signal. From above results, a mechanism of the perception of clicks perceived at onset or offset of the masker is discussed.