Examples of Sound Level Measurements

Concrete Drill

混凝土钻机

Sitting in a faculty office during a quarter break, enjoying the quiet, a faculty member was launched about a meter into the air by the sudden sound of a loud concrete drill directly above his office. After a brief and loud burst, there was again quiet for long enough for him to settle down to work and then another sudden loud burst of noise. After several such episodes removed the possibility of concentration, he decided to measure the sound and collected the following data:

在学期中间休息时坐在教职员工办公室里，享受着安静，一位教职员工突然被头顶上方突然响起的轰隆巨响弹起约一米高。短暂而响亮的爆破声之后，又再次陷入长久的寂静，使他得以恢复平静开始工作，然后又再次突然响起一阵噪音。几次这样的事件使他无法集中注意力，于是他决定测量声音，并收集了以下数据：

Measurement 测量	A Contour 等高线	Flat to 20 kHz 20 kHz 以下
Drill on 钻孔	58 dBA 58分贝A声级	68 dB 68分贝
Background 背景	34 dBA 34分贝A	64 dB 64分贝
Excess over bkg. 背景过量	24 dBA 24 分贝A声级	4dB

Analysis, Concrete Drill Sound

混凝土钻孔声音分析

Sound measurement in decibels inside of buildings can be so misleading as to be worthless since it gives equal weighting to low frequency building sounds to which the human ear has minimal response. This example shows that the use of an A Contour filter gives a much better representation of what the ear hears. Besides the conceptual difference between sound loudness and sound intensity, this example employs the idea of the just noticeable difference in sound level. It also makes use of the rule of thumb for loudness for comparing the before and after loudness, although in this case that is a questionable application since the added sound of the drill is quite different in nature than the background sound to which it is being compared.

在建筑物内部用分贝测量声音时，结果可能如此误导以至于变得毫无价值，因为它对低频建筑噪音给予同等重视，而人耳对此类声音的响应极低。这个例子表明，使用A计数滤波器能更准确地反映人耳的听觉感受。除了声音响度与声音强度之间的概念差异外，这个例子还运用了声音等级的可察觉差异的概念。它还利用了比较前后响度的粗略规则，尽管在这种情况下这种应用是有疑问的，因为新增的钻孔声音的性质与它所比较的背景声音截然不同。

Fire Alarm Measurement

火灾报警测量

Periodic testing of the fire alarm in the physics building provided the opportunity for measurement of the sound level with different filter contours. Measurements were made inside a faculty office down the hall from the alarm. The following data was collected:

对物理大楼内的火灾报警器进行定期测试，提供了使用不同滤波器轮廓测量声音电平的机会。在走廊尽头的教职员工办公室内进行了测量。收集到以下数据：

Measurement 测量	A Contour 等高线	Flat to 20 kHz 20 kHz 以下
Fire Alarm on 烟雾报警器开启	65 dBA 65分贝A声级	71 dB 71分贝
Background 背景	38 dBA 38 分贝A	70 dB 70分贝
Excess over bkg. 背景过量	27 dBA 27分贝A	1 dB 1 分贝

Analysis, Fire Alarm Sound

分析，火灾报警声

Sound measurement in decibels inside of buildings can be so misleading as to be worthless since it gives equal weighting to low frequency building sounds to which the human ear has minimal response. This example shows that the use of an A Contour filter gives a much better representation of what the ear hears. Besides the conceptual difference between sound loudness and sound intensity, this example employs the ideas of the just noticeable difference in sound level and the "rule of thumb" for adding loudness. As suggested with the drill example above, this is not a good application for the rule of thumb for loudness because it is reasonable only if the sounds being compared are similar, whereas the fire alarm and the background noise field are very different in nature.

在建筑物内部用分贝测量声音可能会如此误导以至于变得毫无价值，因为它对低频建筑声音给予同等重视，而人耳对此类声音的响应极低。这个例子表明，使用A计数滤波器可以更准确地反映人耳的听觉感受。除了声音响度与声音强度之间的概念差异外，这个例子还运用了声音水平的可察觉差异以及“经验法则”来加总响度。正如上面钻孔例子所建议的，这种情况下将响度的经验法则应用于此并不合适，因为该法则仅在比较的声音相似时才合理，而火警声与背景噪声在本质上差异很大。