The ratio between the loudest sound we can hear without causing permanent damage and the softest sound we can detect is a million to one, when measured as sound-pressure levels in the air; on the dB scale this is 120 dB. The range of loudnesses we can perceive is called the dynamic range. Sometimes critics talk about the dynamic range that is achieved on a high-quality music recording; if a record has a dynamic range of 90 dB, it means that the difference between the softest parts on the record and the loudest parts is 90 dB—considered high fidelity by most experts, and beyond the capability
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