Intensity Measurement Example

Measured Sound in a Room

房间中的声音测量

If the sound field in a room followed the inverse square law, then each doubling of distance from the source would give a drop of 6 decibels. The descending straight line on the plot at right represents inverse square law behavior, but you can see that the measured sound does not behave like that except in a narrow distance range.

如果房间中的声场遵循反平方定律，那么从声源距离加倍时，声压级会下降6分贝。图中下降的直线表示反平方定律的行为，但可以看出，测量的声场在狭窄的距离范围内才表现出这种行为。

Notes on Room Sound Measurement

房间声音测量注释

Measurements in a laboratory room. Enclosed 6x9 inch speaker, white noise.

实验室房间中的测量。封闭的6x9英寸扬声器，发出白噪声。

#	d(cm) d(厘米)	dB 分贝	dBA dBA（专名或术语）
1	2	90	90
2	4	89.6	89.4
3	8	88.8	88.8
4	16	87.1	87.7
5	32	86	85.4
6	64	81.5	80.6
7	128	77	76.4
8	256	72.2	71.6
9	512	68.8	68.3

The measurements in decibels and dBA were very similar, indicating that the room was fairly free of low frequency, inaudible sounds.

分贝和dBA的测量结果非常相似，表明房间内几乎没有低频不可听的声音。

Click on highlighted text for more detail.

点击高亮文本以获取更多细节。

Effect of Doubling Distance

加倍距离的影响

If the inverse square law applies, then doubling the distance from a point sound source will cause the intensity to drop by 6 decibels. The intensity difference in decibels between two sounds A and B is given by

如果反平方定律适用，那么远离点声源的距离加倍将导致强度下降6分贝。声音A和B之间的强度差（以分贝为单位）为

If sound B is measured at double the distance of sound A from a point source so that it follows the inverse square law, then its intensity will be one fourth that of A. The difference in decibels is then

如果声音B与声音A相比，从点源处测得的距离是声音A的两倍，因此遵循平方反比定律，那么其强度将是A的四分之一。此时分贝的差值为

In a real room, reverberation will contribute to the sound field so that the sound will not drop off as rapidly as the inverse square law predicts.

在真实房间中，混响会贡献于声场，使得声音衰减速度不会像逆平方定律所预测的那样迅速。