Evaluation of Sound Enviroment In House by Instantaneous Sound Intensity

1998 Fiscal Year Final Research Report Summary

• Project/Area Number: 09660182
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 林産学
• Research Institution: Nagoya University
• Principal Investigator: KIMURA Shiro School of Agricultural Science, Nagoya Univeristy Professor, 農学部, 教授 (30023443)
• Co-Investigator(Kenkyū-buntansha): YOKOCHI Hideyuki School of Agricultural Science, Asociate Professor, 農学部, 助教授 (60124723)
• Project Period (FY): 1997 – 1998
• Keywords: Sound intensity / Residence / Sound environment / wall / ceiling / floor / Reflected sound / absorbed Sound.

Research Abstract

In a room, a person listens simultaneously to the direct sounds from various sound resources and to the indirectly reflected sounds (reverberation sound) from wall, ceiling and floor. As for comfortable sound environment for a person, the absorbed sound and the reflected sound of ceiling, wall and floor are set up in balance and the acoustic field in a room has an appropriate reverberation. In this study, the propagation, the absorption and the reflection of sound in a room are investigated with the complex sound intensity. The complex sound intensity consists the active component represents the acoustic energy flow and the reactive component does the standing wave in acoustic fields.
The conventional sound intensity gives a time-varying intensity. However it is impossible to evaluate the propagating sound, in the case that the sampling period for analyzing the sound intensity is long. Then it is possible to analyze approximately the time-frequency sound intensity by the sampling period 1mS.The experiments carried out in a room that the wall and floor were concrete and the ceiling was the absorbing material. A loudspeaker radiated a sound that the amplitudes of 1kHz, 5kHz, 10kHz sinusoidal wave were exponential decreasing. The results present as follow.
The symbol of active sound intensity of the direct sound from a loudspeaker was positive and that of the reflected sound from wall, floor was negative. The distinctions between the direct sound from a loudspeaker and the reflected sound from the concrete wall, floor could be evaluated by the measurement of the sound intensity. The absolute sound intensity of the reflected sound from the ceiling was smaller than that from the wall, floor. In the future, the instantaneous sound intensity will evaluate the sound environment in a house very well.