Acoustics

Sound has different parameters. Major parameters are sound frequency, sound intensity and sound pressure.

The SI unit of frequency is hertz (Hz).
Sound intensity is the sound power per unit area, the SI unit is Watt per square metre (W/m²).
Sound pressure is the difference between the pressure caused
by a sound wave and the ambient pressure of the medium it is passing through. The SI unit of sound pressure is pascal (Pa).
Decibel (dB) a relative unit of measurement widely used in acoustics. However, the dB is not a unit in the sense that a metre is units of length. The decibel is a logarithmic unit used to describe a ratio between the measured level and a reference or threshold level
of 0 dB. The ratio may be sound power, sound pressure, or sound intensity, etc.