The diffraction of an acoustic wave by a penetrable strip introducing the Kutta-Joukowski condition is investigated. Mathematical problem which is solved is an approximate model for a noise barrier which is not perfectly rigid and therefore transmits sound. The problem is solved using integral transforms, the Wiener-Hopf technique and asymptotic methods. It is found that the field produced by the Kutta-Joukowski condition will be substantially in excess of that in its absence when the source is near the edge. Finally, physical interpretation of the result is discussed.

View full abstract

Palatalized articulation (PA) is frequently observed in speech uttered by postoperative cleft palate patients. Provided the acoustical and perceptual cues of PA can be found, speech therapists will be able to use these cues to diagnose PA non-invasively and objectively. We tested human perception of certain synthetic sounds to verify the cues of the PA of /s/ in Japanese. To synthesize the fricatives, we modified the center frequency and the bandwidth of a complex-conjugate pole pair of an all-pole filter obtained from the linear predictive analysis of the PA of /s/. First, we shifted the center frequency from 1, 000 to 3, 000Hz, while the relative bandwidth, or Q factor, was fixed at 10. Subsequently, we shifted the Q factor from 1 to 10, while the center frequency was fixed at 1, 800Hz. The results of a Perceptual experiment involving nine speech the rapists were conclusive that fricatives having a peak between 1, 600 and 2, 400Hz tend to be identified as the PA of /s/, and fricatives having a peak at 1, 800Hz with the Q factor>5, tend to be identified as the PA of /s/. The two-tube model also showed that a peak around 2kHz characterizes the PA of /s/.

View full abstract

To analyze a reflected sound field from objects is important in acoustical engineering as it pertains to sonar, non-destructive inspection, or diagnosis. This paper presents an analytical technique for calculating the amplitude of reflected sound waves from a fine board array of infinite length in oblique incidence. This theory is based on the assumption that a sound source and a receiving point are located separately and that the restriction is a reflect angle that is the same as an incident one. This is based on geometrical optics. Reflectivity is defined the “sound pressure reflection coefficient” in other words, the ratio of the velocity potential of the reflected sound wave to a calculated one. Furthermore, in order to verify the validity of this approach, several experiments were conducted in air using ultrasonic waves that were at a frequency of 39.80 kHz. The measured values showed good coincidence with the approximately calculated ones. By considering this results, the presented technique is useful to analyze the reflection of sound waves from a fine board array of infinite length.

View full abstract

In order to predict sound fields, particularly in the presence of membranes of arbitrary shape, the present paper introduces a method of numerical analysis that couples acoustic systems to membrane vibration systems, while taking into account membrane permeability. To be concrete, the finite element method is applied to membrane vibration systems, the boundary integral equation method is applied to acoustic systems, and these two systems are coupled in a procedure introducing specific flow resistance of membranes. This method is validated through its application to a two-dimensional problem in which a plane wave is incident upon a membrane stretched in a finite rigid baffle. The results are compared with those obtained by the mode expansion method and good agreement is shown. Subsequently, the effects of membrane properties, such as surface density, tension and flow resistance, on the surrounding sound fields and the acoustic characteristics of the finite membrane are discussed in detail.

View full abstract

A verbal rating experiment on timbre was conducted to compare the Japanese and Chinese adjectives which express auditory impressions. The auditory impression of various kinds of musical sounds was measured by a semantic differential method. Japanese scales were used for the Japanese subjects, and Chinese scales were used for the Chinese subjects. The scales used for both groups had the same literal meanings. The obtained data were analyzed by principal components analysis. The factors of sharpness, cleanness, and potency are obtained for the Japanese and Chinese scales. Most of Japanese and Chinese adjectives having the same literal meanings express similar auditory impressions. However, the pleasantness of sound has a different meaning in both languages. For the Japanese language, the pleasantness is independent from the basic three auditory factors. For the Chinese language, the pleasantness is proportional to the sharpness. Furthermore, in some other adjectives having the same literal meanings, differences of the auditory meanings are observed. We should take care when comparing the studies on verbal attributes of timbre in different languages.

View full abstract

The present paper deals with the Rayleigh radiation pressure which is defined as the time-averaged force per unit area of the wall of a closed vessel when an acoustic field is applied. Previous theories on the Rayleigh radiation pressure are examined critically and erroneous results are noted and rectified. A new theory of radiation pressure on a partially reflecting plate is developed as a function of the linear reflection coefficient and transmission coefficient of the plate. It is shown that the time-averaged Lagrangian pressure does not depend on the Lagrangian coordinate and that the effects of acoustic straining cannot be disregarded even in the presence of reflected waves in a closed tube. The present theory is applicable to various types of reflectors. The principal conclusion of this work is that the Rayleigh radiation pressure on a perfectly absorbing plate and that on a perfectly reflecting plate are both given by (γ+1)‹E›/4, where γ is the ratio of specific heats of the medium and ‹E› is the time-averaged energy density.

View full abstract