‘SPL’ stands for Sound Pressure Level, and it is a relative measure of sound pressure compared to the ambient or atmospheric pressure. It is measured in dB, which is a logarithmic measurement (based on human perception) used to express the ratio between two physical quantities.

There are many different references used to calculate dB, which means that there are different standards used for measuring different things. For SPL, atmospheric pressure at a standard temperature and humidity is used as a reference (20μPa), and the unit for these measurements is ‘dBSPL’.

diagram showing various examples of sound sources at different Sound Pressure Levels (SPLs)

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