Strong (short wavelength) noises always travel. Owl, for example, can converse over great ranges because their long-wavelength guffaws are capable to diffract over forest trees and go further in comparison to the songbirds’ short-wavelength tweets. For instance, the TWEETER of a loudspeaker is shaped in the form of a fan for this purpose. Several forest-dwelling birds make use of long-wavelength sound waves diffractive capacity. Īs a result of their capability of diffraction, low frequency sounds are difficult to localize or contain in an environment (see CANYON EFFECT, DIFFUSE SOUND FIELD ).Īn acoustic radiator must be specially designed for good dispersion of high frequencies since this does not occur naturally through diffraction. Ĭompare: CANCELLATION, INTERFERENCE, PARABOLIC REFLECTOR, REFLECTION, REFRACTION. Thus, diffraction may aid sound dispersion and DIFFUSION. When sound waves diffract through a single slit, do they produce an interference pattern which is mathematically identical to that of light waves.
When the wavelength is similar to the dimensions of the object, as with low frequencies and buildings, or mid-range frequencies and the head, the wave diffracts around the object, using its edges as a focal point from which to generate a new wavefront of the same frequency but reduced intensity. Low frequency sounds have wavelengths that are much longer than most objects and barriers, and therefore such waves pass around them undisturbed. Such is the case with high frequencies with respect to the head, and thus is important in BINAURAL HEARING. Waves can spread in a rather unusual way when they reach the edge of an object this is called diffraction.
High frequency sounds, with short wavelengths, do not diffract around most obstacles, but are absorbed or reflected instead, creating a SOUND SHADOW behind the object. The phenomenon in SOUND PROPAGATION whereby a SOUND WAVE moves around an object whose dimensions are smaller than or about equal to the WAVELENGTH of the sound.