Takesaburo Yanagisawa

A three-dimensional sound intensity measurement system for sound source identification and sound power determination by ln modelsa)

This paper describes a full vector intensity probe which advances the field of sound intensity and sound source direction estimation using six matched rotating and variable directional microphones. The probe has three pairs of microphones at an equal spacing of 30 mm that are set up in each of the x, y, and z directions and share the same observation point. The calibration method using the rotating microphone system is effective to correct position errors in the y- and z-axes microphone pairs. Sound intensity measurements using the variable directional microphone method can locate with accuracy a sound source, i.e., the structure parts radiating most acoustic energy. The system can find the maximum sound intensity level and beamwidth of the major lobe, and the peak sound intensity levels of the minor lobes. Therefore, a procedure for sound power determination based on minimum measurement data is theoretically and experimentally discussed. Consequently, it is possible to reconstruct only parts of the syste...

Acoustic characteristics of an electrodynamic planar digital loudspeaker

In this paper, an electrodynamic planar loudspeaker driven by a digital signal is experimentally discussed. The digital loudspeaker consists of 22 voice coils, 11 permanent magnets, a diaphragm with streamlined sections molded in plastic, and a suspension made of handmade Japanese paper between the diaphragm and the frame. First, the acoustic responses are affected by the arrangement of the voice coils, so an asymmetric arrangement is studied. This asymmetric arrangement is designed to obtain as flat a frequency response to an analog signal as possible. This arrangement is compared with a symmetric one and results show that the flatness of the frequency response around 1 kHz and 4 kHz is improved and that the sound reproduction band is from 40 Hz to 10 kHz. Second, to evaluate the acoustic responses to a digital signal, the digital loudspeaker is driven with a pulse code modulation signal. Results show that the digital loudspeaker can reproduce pure sound with a total harmonic distortion of less than 5% from 40 Hz to 10 kHz, exceeding this value only in a narrow frequency band near 4 kHz. This digital loudspeaker was demonstrated to have good linearity over its dynamic range of 84 dB.

Acoustic characteristics of an electrodynamic planar digital loudspeaker using noise shaping technology

The present study extends our previous work [Furihata et al., J. Acoust. Soc. Am. 114, 174-184 (2003)] by investigating our electrodynamic planar loudspeaker when driven by a 12 bit digital signal with noise shaping. Changing the structure of the loudspeaker can lead to improvement, but in this paper improvements that can be made using signal processing are investigated. Results show that the digital loudspeaker demonstrated good linearity over its 84 dB dynamic range from 40 Hz to 10 kHz. This shows that a 12 bit digital loudspeaker which is equivalent to a 16 bit one is possible.

The application of a noise‐rating scale composed of hue‐scale and LAeq on various kinds of noise sources for noise map

In addition to reporting the results of measurements of existing environmental noise and the results of calculations of noise from projected activities, the application of color for representing in terms of noise zones may be useful (ISO 1996‐2). Between color and noise, in spite of differences, there exists an interaction, although the connection between the visible and the audible expression is subjective. Subjectivity can in a given moment become objective, if one succeeds in unifying the visible and the audible. In the case of colored paper on a white background, the relation between the hue level expressing the psychological effect (annoyance) and LAeq(5min) (dB) of typical noise sources was discussed in a laboratory experiment. According to the obtained noise‐rating scale, the seven‐hue scale and LAeq(5min) are correlated well (r=0.874) as follows: white (value V9; not at all bothersome) ⇔ below 26 dB, light blue (hue 2.5B, value 8/chrome 4; not bothersome) ⇔ 26 to 37 dB, light green (2.5BG, 7/8; no...