SampleRate is an option for sound primitives which specifies the number of samples per second to generate for sounds.
The default setting is SampleRate
The highest frequency in hertz that can be present in a particular sound is equal to half the setting for SampleRate.
See the Mathematica book: Section 1.9.13.
See also: SampleDepth.
This gives the rate at which functions are sampled to produce sounds (this number will be different on different platforms).
You will get noise by playing a sound that oscillates at close to the sample rate.
Evaluate the cell to see the graphic and hear the sound.