what is the soun below 20Hz called?
how loudness and pitch be determined
The sound of frequency below 20 Hz is called infrasonic sound.
Loudness: Loudness is the property by which a loud sound can be distinguished from a faint one, both with the same pitch and quality. The loudness or softness of a sound is determined by wave amplitude (or intensity). However, loudness is not the same as intensity.
Pitch: Pitch is another characteristic of sound waves. It allows distinguishing between two sound waves travelling with the same speed and arriving at our ears at the same time. How our brain interprets the frequency of an emitted sound is called its pitch. The faster the vibration of source of sound, higher is the frequency and higher is the pitch. Pitch is that characteristic of sound by which an acute (or shrill) note can be distinguished from a grave or flat note. Pitch of a note depends on the wavelength or frequency of a wave.
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