Evaluation of Sound Enviroment In House by Instantaneous Sound Intensity

在房间里，一个人同时听到来自各种声音源的直接声音和来自墙壁、天花板和地板的间接反射声音（混响声音）。对于人舒适的声音环境，天花板、墙壁和地板的吸收声音和反射声音被平衡地设置，并且房间中的声场具有适当的混响。本文采用复声强研究了声在室内的传播、吸收和反射。复声强是由声场中的有功分量和无功分量组成的，有功分量代表声场中的声能流，无功分量代表声场中的驻波，而常规声强给出的是一个时变的声强。然而，在用于分析声音强度的采样周期长的情况下，不可能评估传播的声音。实验在一个墙壁和地板为混凝土，天花板为吸声材料的房间中进行。扬声器发出1kHz、5kHz、10kHz正弦波幅值呈指数递减的声音。结果表明：扬声器直达声的有源声强符号为正，墙壁、地板反射声的有源声强符号为负。通过声强的测量，可以区分扬声器的直达声和混凝土墙、地板的反射声。天花板反射声的绝对声强小于墙壁、地板反射声的绝对声强。将来，瞬时声强将很好地评估房屋内的声环境。

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.