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Audio therapy is the clinical use of recorded sound, music, or spoken words, or a combination thereof, recorded on a physical medium such as a compact disc (CD), or a digital file, including those formatted as MP3, which patients or participants play on a suitable device, and to which they listen with intent to experience a subsequent beneficial physiological, psychological, or social effect.
The ultrasound within tissue consists of very high frequency sound waves, between 800,000 Hz and 20,000,000 Hz, which cannot be heard by humans. Some of the advantages of ultrasound as a diagnostic and therapeutic tool include its safety profile, lack of radiation, portability, and low cost. [4]
Frequencies below 20 Hz are generally felt rather than heard, assuming the amplitude of the vibration is great enough. Sound frequencies above 20 kHz are called ultrasonic. Sound propagates as mechanical vibration waves of pressure and displacement, in air or other substances. [5] In general, frequency components of a sound determine its "color ...
[6] [7] [note 1] Under ideal laboratory conditions, humans can hear sound as low as 12 Hz [8] and as high as 28 kHz, though the threshold increases sharply at 15 kHz in adults, corresponding to the last auditory channel of the cochlea. [9] The human auditory system is most sensitive to frequencies between 2,000 and 5,000 Hz. [10]
Scientific pitch, also known as philosophical pitch, Sauveur pitch or Verdi tuning, is an absolute concert pitch standard which is based on middle C (C 4) being set to 256 Hz rather than ~ 261.63 Hz, [a] making it ~ 31.77 cents lower than the common A440 pitch standard.
Humans normally hear sound frequencies between approximately 20 Hz and 20,000 Hz (20 kHz), [18]: 382 The upper limit decreases with age. [18]: 249 Sometimes sound refers to only those vibrations with frequencies that are within the hearing range for humans [19] or sometimes it relates to a particular animal. Other species have different ranges ...
In instruments with undamped strings (e.g. harps, guitars and kotos), strings will resonate at their fundamental or overtone frequencies when other nearby strings are sounded. For example, an A string at 440 Hz will cause an E string at 330 Hz to resonate, because they share an overtone of 1320 Hz (the third harmonic of A and fourth harmonic of E).
Very high power levels of 160 dB were achieved at frequencies of 2–3 Hz. Test frequencies ranged from 0.5 Hz to 40 Hz. Test subjects suffered motor ataxia, nausea, visual disturbance, degraded task performance and difficulties in communication. These tests are assumed by researchers to be the nucleus of the current urban myth. [2] [3]