Why is the diffraction of sound waves

The frequency of sound waves varies from 20 Hz to 20,000 Hz with a wavelength of 15 m to 15 mm respectively. The diffraction of sound takes place when the size of the

slit is comparable to the wavelength of the sound. The wavelength of visible light is 0.4 to 0.7 micron. The diffraction of the light doesn’t take place when the size of the

slits is different from the wavelength of the visible light.