Sound wave have frequencies 20 Hz to 20 kHz. The corresponding wavelengths are 15m and 15mm, respectively. Diffraction effects are seen if there are slits of width α such that.
α : λ
For light waves, wavelengths 10–7m. Thus diffraction effects will show when
α : 10–7 m.
whereas for sound they will show for
15mm < α < 15m .