A tone generator, also known as a signal generator, can be described in at least two contexts: electronic audio acoustics and equipment testing and setup, or informational signals commonly associated with a telephone system. In each case, electrically generated audio pulses are sent to specific components. In the case of audio equipment testing, frequency response and sound evaluation are noted. Also, acoustic properties of a studio or hall may be determined. With a telephone system, the dial tone, busy signal, and ring tone are the result of this pulsed tone generation.

When testing audio equipment a tone generator sends out a sound pulse, or test tone, either solid or wavering, at specified octaves and frequencies that can be measured using either an oscilloscope when testing equipment, or with a sound-level meter when determining the acoustical properties of a room or certain audio receivers.

Tone generators will not only generate, but may also be used to replicate certain electronically produced or recorded audio signals. The results of these signals are described variously as white noise or pink noise, this noise depiction depending on the energy level of the sound pulse.

The sound pulses, sent by the tone generator and recorded on an oscilloscope, may be seen as sine waves, a sound-wave pattern generated at 20 hertz (Hz) to 20 kilohertz (kHz), the basic range of audio frequency. The variations in the highs and lows of the sine wave, as well as the distance between them determine the effectiveness of audio equipment, both in receiving and producing certain sounds along predetermined points within the audio frequency range.

Other representations of tone generator pulsations and frequency generation include a sawtooth wave, a triangle wave, a square wave, and various others. These particular representations indicate loudness, harmonics, and/or decreasing or increasing energy levels of the tone generator audio impulses. These impulses, of a specific tonal quality and energy, may be visually interpreted on the oscilloscope through the depiction of a particular pattern. One pattern combining harmonics and pulse energy will resemble a series of triangles, another, a sawtooth pattern, another squares, and so on.

Thus in its most frequently used context, a tone generator tests the various frequency-response qualities of sound reproduction devices, and are also used evaluate the acoustics of the room where the signals are heard. The result is listening pleasure. In its other, less common context, just pick up the telephone to experience its result.