sound

In a human being, sound is captured by the ear and sent to the brains as nerve ( electrical ) signals. It is the biological equivalent to a microphone. 

What is Safe Listening ?

Medias and health care practicioners talk regularily about hearing loss caused by excessively loud noises or listening to music at high volume. State authorities in charge of health and safety in the workplace have define acceptable levels, and especially the duration of sound exposure, since the effects of loud sound exposure cumulate with time.