方法观察模块浓度的不同所致颜色与透明度的变化，并对PAA模块的声学特性包括密度、声速及声衰减进行测量。
Methods The color and transparency of different concentration phantoms were observed. Properties including density, acoustic speed and acoustic attenuation of PAA gel phantom were measured.
研究表明：护耳器现场使用实际声衰减值低于实验室值，其原因是护耳器的实验室测量条件较为严格。
The real decibel attenuation of the hearing protector in the workplace is lower than the value measured in the laboratory, because the measuring conditions in the laboratory are more strict.
基于声衰减原理进行水体含沙量测量的方法，需要测量声压的衰减值。
Based on the principle of sound attenuation to measure the sediment concentration of suspensions, the attenuation value of sound pressure must be detected.
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