Sound Pressure Level Formula = 20 log (p/po) where p is the sound pressure and po is the reference sound pressure of 0.00002 pascals = 0 dB the threshold of hearing at 1 kHz. … Sound Pressure Terms and Definitions … Sources at 1 mSound PressureSPL re 20 μPaTV studio0.0002 Pa20 dBReference sound pressure0.00002 Pa0 dBSound pressure terms and definitions – acoustic glossary www.acoustic-glossary.co.uk › sound-pressure