A loudness perception model for repeated impulsive sounds that have exponentially rising and decaying envelopes was studied. The loudness of repeated impulsive sound is the same as that of a single burst of impulsive sound up to a certain repetition rate. A critical repetition rate R0 beyond which the loudness increases with increase in rep-etition rate was found to lie between 0.2 and 0.7 Hz. In other words, the critical time period, 1/R0, was 2∼5 s. If it is assumed, therefore, that our auditory system has a capacity to hold loudness sensation for 2∼5 s, the result of our experiment can be ex-plained. An integrator of loudness which has a rise time constant of 100 ms and a decay time constant of 5 s yields a good descriptor of the experimental results.

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This paper presents contour charts for the A-weighted sound exposure level of noise generated during passage of a single vehicle. The ground effect has been taken into account for two types of surfaces. The results can be used for prediction of the equiv alentcontinuous A-weighted sound pressure level of traffic noise.

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Emotional expression of four levels of six kinds of sound (aircraft noise, train noise, road traffic noise, speech, music and construction noise) was examined using the method of selected description in five countries-Japan, Sweden, West Germany, China and the U. S. Subject were asked to select the adjectives which they thought appropriate for expressing the impression of each sound. Using the method of selected description, the differences and similarities between sound sources and use of adjectives were expressed more clearly than when conventional semantic differential was used. On the basis of the adjectives selected and cluster analysis, it was found for sounds used in this experi mentthat “loud” in Japan, Sweden and China has neutral connotations while “loud” in Germany and the U. S. has negative connotations. It was also suggested that “noisy” and “annoying” are not differentiated in Japan, while in the other four countries these two adjectives are differentially used.

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Characteristics of leaky surface waves propagating on Lit₂B₄O₇ substrate with a thin aluminum plate are theoretically calculated. Phase velocity, TCD and propagation loss are shown when the thickness (H) of the aluminum plate is changed on a (0, θ, 75°)-cut for 60°<0<80° and a (45°, 90°, ψ)-cut for 55°<ψ<75°, which have zero TCD of leaky surface waves for an electrically open surface. The (0°, 73°, 75°)-cut with H/λ=0.02 of aluminum and the (45°, 90°, 70°)-cut with H/λ=0.027 have zero TCD for both elec-trically open and aluminum short surfaces. Temperature dependence of fractional time delay (Δτ/τ) and propagation loss is also shown.

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The method for calculating loudness level proposed by Zwicker is standardized in ISO 532B. This is a graphical procedure and it can be tedious to calculate loudness level by this procedure. Recently, DIN 45631 has been revised including a computer program for calculating loudness level in BASIC which runs on IBM-compatible PC's. Since the NEC PC-9801 series computers are popular in Japan, the program has been modified for the NEC PC-9801 series computers and is introduced in this paper.

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