This paper describes an improved model of the sound sources which were reported in the previous paper [K. Matsuzawa, Acustica 37, 241-248 (1977)]. Each sound source consists of a vibrator for use at 20kHz, a metallic horn, and a thin metallic diaphragm in flexural vibration. The efficiency and some of the near-field properties for this improved model were reported in the previous short note [Y. Sasaki et al., J. Acoust. Soc. Jpn.(E) 1, 209-210 (1980)]. In this paper, the far-field properties are described and in addition near-field properties. The intense sound field near the diaphragm is confined in a region of some centimeters. The radiation pattern at 1m distance has a single peak or double peaks about a peculiar direction. Numerical studies have been made using the theoretical formulas given in the previous paper. Though the improvement in strength caused a little discrepancy between the real construction and the theoretical counterpart, the experimental results are in good agreement with the calculated ones with respect to both the near-field and the far-field properties.

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In an auditorium, an absorbent boundary is used in order to control the reverberant field. Its reflection composes a part of the early reflections and can not be neglected to estimate the transfer function. The sound reflection coefficient is defined as an unknown function of the integral equation of the first kind, referring to the reflection of a surface element on a rigid plane. It is very difficult with the equation to determine the coefficient which changes depending on incident and reflection angles. When a panel covered with a surface having a reflection coefficient which changes continuously and smoothly is large enough, the kernel function leaves the contribution around the specular reflection point and then the coefficient there can be separated experimentally. The reflection of a panel of limited dimension with such a reflection coefficient is approximately obtained by the convolution of the coefficient and the reflection of the rigid panel at the same position of the panel. Calculated and measured results are compared in the time and frequency domains. This method is also applied to a convex and a concave panel covered with a layer of such a reflection coefficient. The reflection of a panel with a mutual arrangement of strips of two different reflection coefficients is also discussed.

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In a previous work we have obtained evidence to the phonetic similarity between the five Japanese and Spanish vowels. A perceptual correspondence between syllables of both languages was also indicated. In the present study we have included a larger sample of Japanese syllabic sounds. Similarities and differences were determined by using identification tests under normal and distorted conditions (syllable played backwards). One hundred Japanese syllables were presented to ten Spanish-speaking listeners. They were instructed to listen to and to transcribe the sounds using their own Spanish alphabetic symbols. All five vowels were identified with high accuracy, whether presented alone (96%), with another vowel (97.5%), or paired with consonants (94%). The consonants in CV syllables reached an average level of identification of 89% and CVV syllables of 72%. When presented under distorted conditions, patterns of identification and patterns of confusion for each one of the sounds, common to both systems, were similar. Vowels remained unchanged. With exception of stops [p][t][k] and [d] and fricative [3], consonantal sounds were also reversible. It is concluded that a considerable number of Japanese syllabic sounds have a perceptual equivalent in the Spanish syllabic system. The acoustical distribution within the temporal syllabic segment seems to be a relevant factor in the perceptual similarity.

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A relationship between normal modes and rays in the underwater sound field is investigated numerically. Acoustic energy flow along ray path is supplied by the ihterference of neighboring modes. At low frequencies surface or bottom interaction causes disagreement between mode interference cycle distance and classical ray cycle distance. If the number of summed modes decreases, the energy flow becomes fuzzy and the sound field shows the feature of individual mode.

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The loudness of impact sound which has a steady part is compared in this paper with one having no steady part. PSE for loudness of impact sound with steady part longer than ten odd ms corresponds well to its sound energy level, while it shows a rather higher level for the steady duration of about 10ms or less. This difference is explained by the spread of frequency spectrum for the shorter duration. A method to compensate for this deflection of PSE from energy rule is to apply the weighting function of 6-8dB/oct to components beyond the critical band around carrier frequency. PSE for loudness of impact sound corresponds to the peak sound energy level observed through a time window of the form “exp (-βt)”, where β is the damping constant of 5-10. This value of β is equivalent to the time constant of 100-200ms in a square circuit of a sound level meter. And the mean value of readings of SPL measured by the sound level meter with 5ms time constant and the one measured by the meter with 125ms time constant may well describe the loudness of impact sound even when its duration is very short.

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