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在水声测量中常需要有一个能在水下发送已知声级的标准噪声源。标准声源的声源级通常是用离声源有效声中心1m远处的声压级L_s来表示。同样,标准噪声源是用离声源有效声中心1m远处的压谱级L_(ps)表示。压谱级的定义为:声在某一频率的压谱级就是以这个频率为中心,宽度为1Hz的频带中所有声能的有效声压级。由于实际工作中所用滤波器的带宽都大于1Hz,故压谱级是不能直接量得的,而是计算得到的,其计算公式为:
In acoustic measurements it is often necessary to have a standard noise source capable of transmitting a known sound level underwater. The sound source level of a standard sound source is usually represented by the sound pressure level L_s 1 m away from the effective sound center of the sound source. Also, the standard noise source is represented by the pressure spectrum level L ps at a distance of 1 m from the effective sound center of the sound source. The definition of the pressure spectrum level is: the pressure spectrum level of the sound at a certain frequency is the effective sound pressure level of all the sound energy in the frequency band of 1Hz with this frequency as the center. Since the bandwidth of the filter used in the actual work is greater than 1Hz, the pressure spectrum level can not be directly measured, but calculated, which is calculated as: