Editing Pure tone (section)

{{Short description|Sound with a sinusoidal waveform}}
[[File:Wave_sine.svg|right|thumb|A pure tone's pressure waveform versus time looks like this; its frequency determines the x axis scale; its amplitude determines the y axis scale; and its phase determines the x origin.]]

In [[psychoacoustics]], a '''pure tone''' is a sound with a [[sinusoidal]] [[waveform]]; that is, a [[sine]] [[wave]] of constant [[frequency]], [[phase-shift]], and [[amplitude]].<ref>[[ANSI S1.1-1994|ANSI S1.1-1994 Acoustical Terminology]]</ref>
By extension, in [[signal processing]] a single-frequency tone or pure tone is a purely sinusoidal [[signal]] (e.g., a voltage).
A pure tone has the property – unique among real-valued wave shapes – that its wave shape is unchanged by [[linear time-invariant system]]s; that is, only the phase and amplitude change between such a system's pure-tone input and its output.

Sine and cosine waves can be used as [[Basis function#Fourier basis|basic]] building blocks of more complex waves.  As additional sine waves having different frequencies are [[Superposition principle|combined]], the waveform transforms from a sinusoidal shape into a more complex shape.
When considered as part of a whole [[spectrum (physical sciences)|spectrum]], a pure tone may also be called a ''spectral component''.

In clinical [[audiology]], pure tones are used for [[pure-tone audiometry]] to characterize hearing thresholds at different frequencies.
[[Sound localization]] is often more difficult with pure tones than with other sounds.<ref>{{cite journal|author=Stanley Smith Stevens and Edwin B. Newman|title=The localization of actual sources of sound|journal=The American Journal of Psychology|date=1936|volume=48|issue=2|pages=297–306|doi=10.2307/1415748|jstor=1415748}}</ref><ref>{{cite journal|last1=Hartmann|first1=W. M.|title=Localization of sound in rooms|journal=The Journal of the Acoustical Society of America|date=1983|volume=74|issue=5|pages=1380–1391|doi=10.1121/1.390163|pmid=6643850|bibcode=1983ASAJ...74.1380H}}</ref>