Sound

A sound is produced by the initiation of a succession of compressive and rarefactive disturbances in a medium capable of transmitting these vibrational disturbances. Particles of the medium acquire energy from the vibrating source and enter the vibrational mode themselves. The wave energy is passed along to adjacent particles as the wave passes through the medium

Examples of Vibrating Elements Vibrating Reeds. Ie clarinet and saxophone.

Strings. Ie. Guitar, vocal cords

Membranes. Ie. Drum, loud speaker

Air columns. Ie Pipe organ, flute

Frequency Range The frequency range in which sound occurs is called the sonic spectrum. The lower limit of the sonic spectrum is not well defined. For example, in an earthquake the frequency may only be a fraction of a wave per minute.

The upper limit of the sonic spectrum is well defined. For waves traveling with a constant velocity, as frequency increases, wavelength decreases. Eventually, wavelength will become so small that a particle will not be able to transfer its energy to adjacent particles.

For ordinary temperatures and pressures, the upper range of the sonic frequency range is of the order of 10 9 hertz in a gas. For solids and liquids, the upper range of the sonic spectrum is higher because the particles are more closely spaced together.

Definitions Audio range – a range of compression wave frequencies to which the human ear is sensitive. For humans, the audio range is 20 hz – hz. Ultrasonic – sound waves with frequencies above the audio range. Infrasonic – sound waves with frequencies below the audio range.