Being able to hear different sounds depends on different parts of the entire hearing mechanism and the movement of these parts. The eardrum or tympanic membrane is the beginning. The movement of the eardrum triggers movements of other structures in the middle and inner ear and also in the cochlea. Then the movement of these structures sends nerve impulses to the brain. Frequency (pitch) and intensity (loudness) is how the ear differentiates between sounds. Knowing about the physics of sound and hearing can help in the understanding of the function of the ear’s structures and how sound is processed through them.
Intensity of sound is the “loudness” of a sound and is measured in decibels (dB). 0dB is the beginning of the decibel scale. The measurement of 0dB does not mean there is no sound. It is the lowest point at which sound can be perceived by a person with average hearing..
Since humans can hear a wide range of sound intensities the decibel scale is based on multiples of ten. For example 10dB is ten times the intensity of 0dB. Sounds that are greater 85dB can caused hearing damage and are known as noise-induced hearing loss.
The number of cycles in one second is known as frequency. Frequency is measured in hertz (Hz) and is perceived by the ear as pitch. The higher number of cycles is known as “high-pitched” and the lower number of cycles is “low-pitched”.
Wavelength is also related to frequency. As frequency increases, wavelength decreases. To repeat a large number of cycles in one second a sound wavelength is short. The higher the number of cycles, the higher the pitch, and the shorter the wavelength.
Hearing loss can have an effect on speed perception and communication since speech sounds have a combination of frequencies and intensities.
Sat, Jul 10, 2010
Health