What is Sound? (terms and concepts)

Sound Wave

A longitudinal wave that is caused by vibrations and that travels through a material medium

Transverse

The particles of the medium vibrate at a 90-degree angle to the direction the wave is traveling. Think of a rope being shaken up and down to create a wave that travels horizontally along the rope.

Longitudinal

The particles of the medium vibrate parallel to the direction the wave is traveling. Sound waves are a classic example of this type of wave, where air particles are compressed and then spread apart, creating areas of high and low pressure that move through the air.

Compression

Areas of high pressure within a longitudinal sound wave, where the particles of a medium (like air) are squeezed closely together.

Rarefaction

The region of a longitudinal wave where the particles of a medium are spread farther apart, creating an area of lower density and pressure

Frequency

The rate of vibration in a sound wave, measured in Hertz (Hz) or cycles per second, which determines the perceived pitch of a sound.

Cycles per Second (cps)

Old term for hertz (Hz), the unit used to measure the frequency of a sound wave.

Hertz (Hz)

The unit of measurement for frequency representing the number of sound wave cycles per second.

kiloHertz (kHz)

1,000 Hertz (Hz)

Pitch

The highness or lowness of a sound, which determined by the frequency of its sound waves.

Fundamental Frequency

The lowest and most dominant frequency within a sound, which our ears and brain perceive as its musical pitch.

Range of Human Hearing

20 Hertz to 20,000 Hz (20 kHz)

Bandwidth

The specific range of frequencies that a piece of equipment or a signal can process or contain.

Octave

An interval where the higher note has exactly double the frequency of the lower note.

Bass

The lowest part of the sound spectrum, generally the frequencies between 20 Hz and 300 Hz, which are characterized by a deep, rumbling quality.

Low Bass

The deepest frequencies of the sound spectrum generally from 20 Hz up to about 80 Hz. 1st and 2nd octaves.

Upper Bass

The frequency range between 80 Hz to 320 Hz. 3rd and 4th octaves.

Midrange

The frequency range between 320 Hz to 2.5 kHz. 5th, 6th, and 7th octaves.

Upper Midrange

The frequency range between 2.5k to 5kHz. 8th octave.

Treble

The frequency range between 5k to 20kHz. 9th and 10th octaves.

Amplitude

The intensity or “loudness” of a sound wave, representing the extent of air molecule compression and stretching as the sound travels.

Decibel (dB)

A logarithmic unit of measurement that expresses the ratio between two sound levels or signal strengths, rather than an absolute value.

Sound Pressure Level (dB-SPL)

A logarithmic measurement, expressed in decibels, that quantifies the intensity or loudness of a sound wave based on the variation in air pressure it creates.

Threshold of Pain

The sound pressure level at which sound causes physical pain in a human listener. Prolonged or excessive exposure can cause permanent hearing damage.

Dynamic Range

The ratio or difference between the softest and loudest parts of a recording or performance, measured in decibels.