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AcousticsdB(SPL) - dB (Sound Pressure Level) — for sound in air and other gases, relative to 20 micropascals (μPa) = 2×10−5 Pa, the quietest sound a human can hear. This is roughly the sound of a mosquito flying 3 metres away. This is often abbreviated to just "dB", which gives some the erroneous notion that "dB" is an absolute unit by itself. For sound in water and other liquids, a reference pressure of 1 μPa is used. dB SIL - dB Sound Intensity Level — relative to 10−12 W/m2, which is roughly the threshold of human hearing in air. dB SWL - dB Sound Power Level — relative to 10−12 W.
Sound levels for nonlinear (decibel) and linear (intensity) scales dB Wm2 type of sound130 10 artillery fire at close proximity (threshold of pain) 120 1 amplified rock music; near jet engine 110 10–1 loud orchestral music, in audience 100 10–2 electric saw 90 10–3 bus or truck interior 80 10–4 automobile interior 70 10–5 average street noise; loud telephone bell 60 10–6 normal conversation; business office 50 10–7 restaurant; private office 40 10–8 quiet room in home 30 10–9 quiet lecture hall; bedroom 20 10–10 radio, television, or recording studio 10 10–11 soundproof room 0 10–12 absolute silence (threshold of hearing)