Understanding the measurement of sound intensity in decibels (dB)

Sound intensity is frequently expressed in terms of decibels (dB). The decibel (1/10 of a Bel) was named in honour of Alexander Graham Bell. It expresses the logarithm to the base 10 of
the ratio between two sound intensities or (sound pressures)².

The
internationally recognised reference standard intensity for sound is 10^-12
watts per m² which corresponds to a sound pressure of 2.10^-5
N/m² (or Pascal). For a pure tone at 1000 Hz this is close to the
threshold of hearing for young healthy adults.

style='mso-bidi-font-weight:normal'>	dB	Sound pressure (N/m2; Pa)	Relative sound Pressure
Jet aeroplane, 80 ft from tai; hair cell damage	120 dB	20	10-6
Busy traffic, shouting	80 dB	2.10 -1	104
Conversational speech	60 dB	2.10 -2	103
Residential area at night	40 dB	2.10 -3	102
Whisper at 5ft	20 dB	2.10 -4	101
Threshold for hearing 1000 Hz young adult	0 dB	2.10 -5	1.0