A few reports on the interference with radio or television listening were presented by means of the social surveys, but there are few investigations on noise evaluation in broadcast listening. This study aimed at obtaining the noise evaluation in broadcast listening and the relation between annoyance of noise and physical parameters such as types of noise, noise level, average frequency of occurrences, and so on. Three types of noise; steady noise, intermittent noise, and impulsive noise, were used in the experiment. Broadcast program was the reading of novels and music. The results showed that the annoyance of the steady noise, the intermittent noise and the impulsive noise was almost determined by L_eq in broadcast listening. Investigated in detail, however, the results showed that the steady noise was the most annoying, the intermittent was the next, and the impulsive was the least annoying.

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The longitudinal wave propagation in a liquid contained in a duct is generally effected by the compliance of the duct walls, causing a reduction of the wave speed. If the duct is rectangular, and is constructed with separate pieces of metal plate, which are assembled together with screws, the wave speed in it is difficult to predict, because the wall motion is unpredictable, caused by location or number or fastening forces of screws or other factors. In this paper, the sound wave speed in low frequencies in a liquid-filled square duct was investigated. Two models were developed for the duct walls, and transmission line theory was used to predict the wave speed. The duct consists of four pieces of aluminum sheet, which were joined together with brass screws. Acoustical impedance at the driving point for open-ended water-filled duct system was measured for the determination of the sound speed. The simply supported beam model for the duct walls predicted wave speed slightly lower than measured values. The more constrained model gavehigher values. Thus, the two models should predict the extremes of the wave speed for practical square ducts.

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By the calculating method reported in the previous paper, the input admittance curves of six shakuhachis of 4 types were obtained. In this paper, the played pitch frequencies were measured and their relation to the correspondent peak frequencies of input admittance was found. From this relation, the magnitude of the acoustic inertance generated at the mouth end and resonance curves under the playing state were calculated. As for the levels at the multiples of the lowest two peak frequencies of resonance curve, their average varying rate per 20 cents change of the pitch frequency was estimated. The rate is about 3.0 dB and 3.6 dB in the lower and higher octave respectively. This rate suggests how much the harmonic levels of played tones vary with the performance of thepitch control techniques as “meri” or “kari.” Based on these values, the arrangement of resonance frequencies which is desirable for the musical expression aimed in pitch control was discussed.

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The parametric interaction of two high frequency radiations in a focusing field produces a nonlinearly generated, difference frequency radiation that is also effectively focused. An analysis of this phenomenon, utilizing the parabolic approximation of the Helmholtz wave equation, has already been developed. The present paper presents anotheranalytical model which makes the numerical computation much easier compared with the solution of the parabolic equation. The primary sound in the model is roughly assumed to be a spherical wave except in the focal region, where it is assumed to bea plane wave. The difference frequency sound pressure is obtained under the quasi-linear assumption by the volume integration of the radiation from the virtual sources, takinginto account the diffraction effect at the difference frequency. The validity of the model is demonstrated through comparison to computed results of the parabolic approximation.

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This paper describes a new automatic method of detecting flaws in ball bearings and classifying them into four categories: normal, flaw on the inner ring, flaw on the outer ring, and flaw on the balls. Detection and classification are currently carried out mainly aurally by inspectors who listen to a vibration signal obtained by a vibration pick-up in an Anderon meter, which is attached to the outer ring of a ball bearing while the inner ring rotates at a uniform speed. There have been some proposals for the automatic detection and classification of flaws which are based on the analysis of the periodicity of vibration pulses excited by flaws. When flaws are slight, however, it is hard to detect them by recently proposed methods because of the following two reasons:(A) the power of the vibration due to flaws is less than that of noise, and (B) the period of flaw pulses is irregular. We have developed a new method, though, by which slight flaws can be detected. We have applied this new method in the flaw detection of small-sized ball bearings: flaws were classified with an accuracy rate of greater than 97% into the above four categories.

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