Pure tone
Sound with a sinusoidal waveform / From Wikipedia, the free encyclopedia
In psychoacoustics, a pure tone is a sound with a sinusoidal waveform; that is, a sine wave of constant frequency, phase-shift, and amplitude.[1] 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 systems; that is, only the phase and amplitude change between such a system's pure-tone input and its output.
![Thumb image](http://upload.wikimedia.org/wikipedia/commons/thumb/c/cd/Wave_sine.svg/220px-Wave_sine.svg.png)
Sine and cosine waves can be used as basic building blocks of more complex waves. As additional sine waves having different frequencies are combined, the waveform transforms from a sinusoidal shape into a more complex shape. When considered as part of a whole 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.[2][3]