有什麼公式可從聲波的振幅來求出聲能?

正弦波的功率與振幅的平方成正比,比例係數與選取的單位,介質等有關.通常聲波為非正弦波,要用傅利葉級數展開,而且振幅時時在變,用振幅求功率很困難,實用中用分貝計測響度,響度與聲強(振幅平方)成對數(log)關係.

Assume each unit volume of air vibrates as a simple harmonic oscillator,
the energy E = (1/2).d.V^2,
where d is the density of air,
V is the max speed of vibration.

But V = w.A
where w is the angular frequency of the sound wave and A is the amplitude.
Hence, E = (1/2).d.[w.A]^2
which is the energy carried by the sound wave per unit volume of air.