Common test signals include the sine wave, the square wave, the triangle wave, the sawtooth wave, several types of noise waveforms, and multitone signals consisting of a superposition of sine waves.
The most common signal for audio testing is the sine wave. A single sine wave is often used to determine the amount of harmonic distortion introduced by a system. Multiple sine waves are widely used to measure the intermodulation distortion or to determine the frequency response. The following table lists the signals used for some typical measurements.
Measurement | Signal |
Total harmonic distortion |
Sine wave |
Intermodulation distortion |
Multitone (two sine waves) |
Frequency response |
Multitone (many sine waves, impulse, chirp), broadband noise |
Interpolation |
Sinc |
Rise time, fall time, overshoot, undershoot |
Pulse |
Jitter |
Square wave |
These signals form the basis for many tests and are used to measure the response of a system to a particular stimulus. Some of the common test signals available in most signal generators are shown in the following figures.
The most useful way to view the common test signals is in terms of their frequency content. The common test signals have the following frequency content characteristics: