what is the unit of sound ?

sound wave is a kind of wave,
its measures the unit of waves,
so you can use Hz(頻率),lambda(波長)and decibel(分貝) for measuring the sounds.

by v = (f)(lamda)
the wavelength and the frequency of sound is INVERSALY PROPORTIONAL,

which maens a sharp sound(high frequency) is low wavelength(not transport to very far at all)

Decibel is the magnitude of the sound,which is the amplitude of waves.

You did not specify the unit for which physical property of sound in your question.

Unit for :-
sound speed --- m/s (metres per second)
sound frequency --- Hz (Hertz, cycles per second)
wavelength of sound --- m (metres)
sound pressure --- Pa (Pascal)
sound intensity --- w/m^2 (watts per square metre)
sound intensity level --- dB (decibel)
sound pressure level --- dB (decibel)
loudness of sound --- phons

the unit of sound intensity is dB (decibel) (the relationship between the intensity and the intensity level 分貝 can be expressed in a logarithmic formula)