We are still talking here about “Bell telephone laboratories”. Bell engineers needed a reliable metric to develop their new telephone devices. So they created the decibel, or one tenth of a Bel – named in honor of their venerable boss, Alexander Graham Bell.

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dB & dBA

In 1933, Harvey Fletcher and W. A. ​​Munson from Bell Telephone Laboratories presented loudness level contours (curves of equal perception of a sound). These curves were obtained statistically following listening tests carried out using listeners with hearing considered to be normal.

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Earing and sound

Earing & Sounds

Sounds are defined as an auditory sensation generated by an acoustic wave (Larousse). This definition introduces two notions: acoustic waves and human hearing. When an acoustic wave reaches the head of a listener, it is picked up by the pinna and directed toward the ear canal. These two elements form the outer ear.

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Sound Waves

A sound wave is a pressure disturbance that propagates through the air. This disturbance can be caused by a vibration (for example the vibrations of the vocal cords) or even turbulence in an air flow, such as a whistle.

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