Refraction of sound
The refraction of sound , also called refraction, is a fundamental phenomenon in the disturbed propagation of sound waves . If a sound wave strikes a boundary surface at an angle at a given angle of incidence α , a certain proportion is usually thrown back into the sound-carrying medium , depending on the physical properties of the sound process and the molecular parameters of the transmission medium (compare sound reflection ), while another part penetrates into the receiving medium and spreads there further. The sound experiences a change in direction at the interface, which is known as refraction.
The change in direction that occurs depends on the ratio of the speed of sound of the supplying c 1 and the receiving c 2 transmission medium. Based on the refractive index in optics, this quotient is called the acoustic refractive index or sound refractive index n :
- .
Basically, the sound becomes the normal line refracted when the acoustic velocity of the feeding medium is greater. In the formula for the acoustic refractive index, c 1 > c 2 . In the opposite case, i.e. c 1 < c 2 , the sound is deflected away from the perpendicular.
The phenomenon of sound refraction has a wide range of practical applications, e.g. B. with acoustic lenses, as they are used both for the collection and for the dispersion of sound, especially in ultrasound technology as well as for sound propagation outdoors.