Sound Science: Basics of Acoustics

Acoustic waves are a type of energy propagation through a medium by means of adiabatic compression and decompression. Important quantities for describing acoustic waves are acoustic pressure, particle velocity, particle displacement and acoustic intensity. Acoustic waves travel with a characteristic acoustic velocity that depends on the medium they’re passing through. Some examples of acoustic waves are audible sound from a speaker (waves traveling through air at the speed of sound), ground movement from an earthquake (waves traveling through the earth), or ultrasound used for medical imaging (waves traveling through the body).

A distinct use of the term sound from its use in physics is that in physiology and psychology, where the term refers to the subject of perception by the brain. The field of psychoacoustics is dedicated to such studies. Webster’s 1936 dictionary defined sound as: “1. The sensation of hearing, that which is heard; specif.: a. Psychophysics. Sensation due to stimulation of the auditory nerves and auditory centers of the brain, usually by vibrations transmitted in a material medium, commonly air, affecting the organ of hearing. b. Physics. Vibrational energy which occasions such a sensation. Sound is propagated by progressive longitudinal vibratory disturbances (sound waves).”This means that the correct response to the question: “if a tree falls in the forest with no one to hear it fall, does it make a sound?” is “yes”, and “no”, dependent on whether being answered using the physical, or the psychophysical definition, respectively.

The physical reception of sound in any hearing organism is limited to a range of frequencies. Humans normally hear sound frequencies between approximately 20 Hz and 20,000 Hz (20 kHz),: 382  The upper limit decreases with age.: 249  Sometimes sound refers to only those vibrations with frequencies that are within the hearing range for humansor sometimes it relates to a particular animal. Other species have different ranges of hearing. For example, dogs can perceive vibrations higher than 20 kHz.

This article includes material from “Acoustic wave.” Wikipedia. Licensed under Attribution-ShareAlike 3.0 United States (CC BY-SA 3.0 US) Authors:

This article includes material from “Sound.” Wikipedia. Licensed under Attribution-ShareAlike 3.0 United States (CC BY-SA 3.0 US) Authors: