Following topics were discussed from the psychological viewpoint of noise assessment: 1) The distinction among loudness, noisiness and annoyance. 2) Validity of the sone scale, and the methods of calculating loudness. 3) Physical descriptors of non-steady state sounds. 4) Psychological methods to evaluate the effects of noise on man.

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Developments and future trends in the standardization of methods for the measurement and evaluation of noise in Japan are reviewed in this paper. They are divided mainly into three parts;(1) standards on measuring instruments, (2) standards on methods for the measurement of environmental noise, and (3) standards on methods for the measurement of noise emitted by machinery, equipment and other sound sources. The last parts are further subdivided into two groups, that is general standards and specific standards which specify test procedures to be adopted for specific sound sources. For the developments of these standards, it is the important principles that the key specifications shall have the sufficient conformities to the corresponding international standards, such as ISO and IEC standards. It is also considered to introduce some amendments and/or supplements based on the recent technical developments and experiences.

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Concerning stationary sound sources, sound power level which describes the sound power radiated by a sound source is clearly defined. For its measuring methods, the sound pressure methods using free field, hemi-free field and diffuse field have been established, and they have been standardized in the international and national standards. Further, the method of sound power measurement using the sound intensity technique has become popular. On the other hand, concerning transient sound sources such as impulsive and intermittent sound sources, the way of describing and measuring their acoustic outputs has not been established. In this paper, therefore, “sound energy level” which represents the total sound energy radiated by a single event of a transient sound source is first defined as contrasted with the sound power level. Subsequently, its measuring methods by two kinds of sound pressure method and sound intensity method are investigated theoretically and experimentally on referring to the methods of sound power level measurement.

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The following aspects of the loudness of impulsive sounds were investigated on the basis of the data from a round robin test in Japan:(1) The propriety of sound exposure level as a measure for the loudness of impulsive sounds.(2) The effects of duration and decay time.(3) The relation between sound exposure level and the peak values measured by means of time constants of sound level meters. Artificial impulsive sounds were used as stimuli and their loudness was judged, using the method of constant stimuli, in 10 different laboratories in Japan. Results showed that sound exposure level has good correspondence with loudness, and that the values of sound exposure level can be approximated by peak levels measured by means of a time constant of 1 s (Slow). Duration, decay time and carrier frequency had no significant effect.

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This paper reports and discusses the results of the second stage of experiments of a round robin test on the evaluation of impact sounds. Two psychological attributes, loudness and noisiness, were dealt with in this study. The PSE's for both attributes were obtained by using the same experimental procedure. In this study, a repeated impulsive sound whose duration is 3 s at the longest was presented in a diotic listening condition. The results of the study are summarized as follows: 1) The coefficients for linear regressions of PSE on L_pE (the frequency-unweighted sound exposure level) were 0.62-0.63 for loudness, while they were 0.93-1.11 for noisiness. This seems to indicate that the time constant for integration of sensation is longer for noisiness than for loudness. 2) For both loudness and noisiness, L_pE showed a high correlation with PSE obtained by our experiments, and thus loudness of repeated impulsive sounds might be described by L_pE with some modifications, and noisiness can be expressed by L_pE with minor modifications. 3) The difference between the results of carrier signals used in this study has little effects on the experimental data.

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This paper describes an active sound control system using an FIR digital filter, which attenuate low-frequency noise in an air-conditioning duct system. This system is a monopole type with two identical microphones located on upstream and downstream sides at equal distances from the cancellation loudspeaker in the duct. The output signals of the two microphones are mixed 180° out of phase with one another, and are fed to the input terminal of the digital filter. This reduces acoustic feedback in the system, offering high performance for duct noise caused by a centrifugal fan in a range of 70 Hz to 600 Hz.

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The impulsive sounds generated from some construction equipments are analyzed by the Wigner distribution. It can be said that one of the appropriate window functions for the Wigner distribution of the sound is the Gaussian window whose length is 1.28 ms corresponding to 6σ by taking account of the cross terms.

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