Reflection and Refraction of Sound

At sound waves obey the same general phenomena of propagation undulatory. Due to its nature, the sound it cannot be polarized, but suffers the action of other phenomena, such as reflection, refraction, interference, diffraction and Doppler effect. Sound is a wave, which is characterized as mechanics as to nature and longitudinal as to its propagation, and it has frequency between 20 hertz and 20,000 hertz.

THE sound wave it is considered mechanical because it needs a medium to propagate and it is longitudinal because the propagation direction coincides with the vibration direction. O human auditory system can only capture sound waves that have a frequency in the range between 20 and 20 000 Hz, however, beings such as bats and dolphins have the ability hearing greater than that of human beings, that is, their auditory system captures sound waves that exceed the frequency of 20,000 hertz, called waves ultrasonics.
sound reflection
Sound waves obey the same laws of reflection as the waveform. The reflection of a sound wave happens when it encounters an obstacle and returns to the propagation source medium. The occurrence of this phenomenon can give rise to two other phenomena, which are called

echo and reverberation. Echo happens when the reflected sound returns after the original sound is completely extinguished. In reverberation, the sound that was reflected reaches the ear before the extinction of the original sound, thus reinforcing the emitted sound.
sound refraction
THE sound refraction also obeys the laws of refraction of the undulatory. Thus, this phenomenon happens when the wave passes from one medium to another with a different refractive index, which causes the propagation velocity variation and wavelength variation, but never the frequency variation, as this is a characteristic of the broadcasting source.
sound diffraction

THE diffraction it is the property that waves have to bypass obstacles and that depends on the length of the propagated wave. By means of the ratio between the wavelength and the width of the obstacle, we can calculate the degree of diffraction of a specific wave which, mathematically, can be written as follows:

r = λ/d

The greater the ratio, the greater the length of the diffraction curve. This is the phenomenon that explains the fact that we can hear behind the door when a person speaks on the other side of the door., besides being an event widely applied in the assembly of loudspeaker systems.

By Marco Aurélio da Silva
Graduated in Physics

Source: Brazil School - https://brasilescola.uol.com.br/fisica/reflexao-refracao-som.htm