Bilingual edition: English is preserved and Chinese follows each unit. Terminology uses the confirmed v20260916 glossary; automated semantic review remains traceable.
中英双语版：英文原文完整保留，中文紧随对应单元；术语采用 v20260916 确认表，自动语义审校结果可追溯。

Sound Intensity

声音强度

Sound intensity is defined as the sound power per unit area. The usual context is the measurement of sound intensity in the air at a listener's location. The basic units are watts/m2 or watts/cm2. Many sound intensity measurements are made relative to a standard threshold of hearing intensity I0 :

声强被定义为单位面积上的声功率。通常情况下，声强的测量是在听众所在位置的空气中进行的。基本单位是瓦特每平方米或瓦特每平方厘米。许多声强测量都是相对于一个标准的听阈声强I₀进行的：

The most common approach to sound intensity measurement is to use the decibel scale:

测量声音强度最常用的方法是使用分贝标尺：

Decibels measure the ratio of a given intensity I to the threshold of hearing intensity, so that this threshold takes the value 0 decibels (0 dB). To assess sound loudness, as distinct from an objective intensity measurement, the sensitivity of the ear must be factored in.

分贝测量给定的强度I与听阈强度的比值，因此这个阈值取0分贝（0 dB）。为了评估声音的响度，而不是客观强度测量，必须考虑耳朵的灵敏度。
 Index

Sound level measurement

Loudness concepts
索引声音电平测量响度概念
 
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Sound Pressure

声压

Since audible sound consists of pressure waves, one of the ways to quantify the sound is to state the amount of pressure variation relative to atmospheric pressure caused by the sound. Because of the great sensitivity of human hearing, the threshold of hearing corresponds to a pressure variation less than a billionth of atmospheric pressure.

由于可听声由压力波组成，量化声音的一种方法是说明声音引起的压力变化相对于大气压力的大小。由于人耳的高灵敏度，听阈对应的压力变化小于大气压力的十亿分之一。

The standard threshold of hearing can be stated in terms of pressure and the sound intensity in decibels can be expressed in terms of the sound pressure:

标准的听阈可以表示为压力，而以分贝为单位的声强可以表示为声压：

The relationship of sound intensity to pressure is discussed below. The pressure P here is to be understood as the rms pressure of the collection of waves which make up the sound. The power carried by a traveling wave is proportional to the square of the amplitude. The factor of 20 comes from the fact that the logarithm of the square of a quantity is equal to 2 x the logarithm of the quantity. Since common microphones such as dynamic microphones produce a voltage which is proportional to the sound pressure, then changes in sound intensity incident on the microphone can be calculated from

下面将讨论声压与声强度之间的关系。这里的压力P应理解为构成声音的波的均方根压力。传播的波所携带的功率与振幅的平方成正比。因数20来源于这样一个事实：一个量的平方的对数等于该量的对数的2倍。由于常见的动态麦克风产生的电压与声压成正比，因此可以利用声压计算作用在麦克风上的声强度变化。

where V1 and V2 are the measured voltage amplitudes .

其中V₁和V₂是测量到的电压振幅。
 Index

Sound level measurement
索引声音电平测量
 
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Threshold of Hearing

听阈

Sound level measurements in decibels are generally referenced to a standard threshold of hearing at 1000 Hz for the human ear which can be stated in terms of sound intensity:

以分贝为单位的声级测量通常参考人类在1000 Hz频率下的标准听阈，这可以表示为声亮度：

or in terms of sound pressure:

或者用声压来表示：

This value has wide acceptance as a nominal standard threshold and corresponds to 0 decibels. It represents a pressure change of less than one billionth of standard atmospheric pressure. This is indicative of the incredible sensitivity of human hearing. The actual average threshold of hearing at 1000 Hz is more like 2.5 x 10-12 watts/m2 or about 4 decibels, but zero decibels is a convenient reference. The threshold of hearing varies with frequency, as illustrated by the measured hearing curves.

这个值被广泛接受为一个名义标准阈值，对应于0分贝。它表示压力变化小于标准大气压的十亿分之一。这表明人类听觉的惊人灵敏度。实际上，1000 Hz频率处的平均听阈更接近2.5 x 10^-12 瓦/平方米或约4分贝，但0分贝是一个方便的参考。听阈随频率变化，如图中测量的听力曲线所示。
Measured threshold as a function of frequency
频率函数的阈值测量
 Index

Sound level measurement
索引声音电平测量
 
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Threshold of Pain

疼痛阈值

The nominal dynamic range of human hearing is from the standard threshold of hearing to the threshold of pain. A nominal figure for the threshold of pain is 130 decibels, but that which may be considered painful for one may be welcomed as entertainment by others. Generally, younger persons are more tolerant of loud sounds than older persons because their protective mechanisms are more effective. This tolerance does not make them immune to the damage that loud sounds can produce.

人类听觉的名义动态范围是从标准听阈到疼痛阈值。疼痛阈值的一个名义数值是130分贝，但对一个人来说可能令人痛苦的声响，对另一些人可能被视为娱乐。通常，年轻人比老年人更能忍受大声响，因为他们的保护机制更有效。这种耐受性并不意味着他们对大声响造成的损害有免疫力。

Some sources quote 120 dB as the pain threshold and define the audible sound frequency range as ending at about 20,000 Hz where the threshold of hearing and the threshold of pain meet.

一些资料将120分贝列为疼痛阈值，并定义可听声频率范围在约20000赫兹处结束，此时听阈和疼痛阈相遇。
 Index

Sound level measurement
索引声音电平测量
 
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Relation of Sound Intensity to Sound Pressure

声压与声强度的关系

Sound travels through air as a longitudinal wave which may contain many frequencies. The intensity of the sound may be expressed in terms of the rms pressure of the collection of waves provided that the average is over at least one period of the lowest frequency contained in the sound. The intensity relationship is analogous to the electric power relationship where the rms pressure is analogous to voltage and the wave impedance of the air is analogous to the electric resistance R.

声音通过空气以纵波形式传播，可能包含许多频率。声音的强度可以表示为波的集合的均方根压力，前提是平均值至少覆盖了声音中最低频率的一个周期。强度关系类似于电功率关系，其中均方根压力类似于电压，而空气的波阻抗类似于电 resistance R。

The acoustic resistance or wave impedance R of air is calculated as the density of the air times the speed of sound in air, R = ρvs. At 20°C and atmospheric pressure this resistance is:

空气的声阻抗或声波阻抗 R 由空气的密度乘以空气中声速得到，R = ρv s 。在20°C和大气压下，该阻抗为：

Since the acoustic resistance is independent of the sound frequency, the intensity can be expressed in terms of the sound pressure level:

由于声阻独立于声频，因此可以将强度表示为声压电平的函数：

The pressure P here is to be understood as the rms pressure of the collection of waves which make up the sound. Making use of the sound intensity associated with zero decibels, I0 = 10-12 watts/m2, the sound pressure level (SPL) P0 associated with the threshold of hearing is

这里的压力 P 应理解为构成声音的波的声压。利用与零分贝对应的声强度 I₀ = 10⁻¹² 瓦/平方米，与听阈相关的声压级（SPL）P₀ 为

This can be used to develop the expression for sound pressure level related to the threshold of hearing above.

这可以用来推导与听阈以上的声压电平相关的表达式。
 Index

Sound level measurement

dB SPL, Stanford
索引声级测量 dB SPL，斯坦福
 
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