Test Tone And Noise Generation

The Stereo Workstation includes a Test Tone and Noise generation mode to exercise your system. The level and frequency of the left and right channel Test Tones can be independently adjusted. The tones can be sine wave, AM or FM, modulated to produce more useful signals when dealing with the human perception of sound. The Workstation can generate cosine tone bursts or continuous tones. The FM modulation plus the AM burst modulation produce tones that have superb imaging characteristics and excellent bandwidth characteristics for use in psychoacoustic experiments and testing. It is this kind of tone that is used in Computer Aided Adjustment sessions. The phase balance between the left channel and right channel tones can also be adjusted. It is instructive to listen to the effects of phase balance on Test Tones. Just by changing the phase balance the tone can be located anywhere in the sound image space from left to right, however this only works for frequencies less than about 1kHz and greater than 200 Hz. The Workstation can generate Uniform Masking Noise (UMN) which has the property that it can equally mask Test Tones of any frequency. The left and right channel UMN can be correlated or uncorrelated and the noise level and balance can be adjusted. The Workstation can also generate Flat Noise which is mathematically flat across the frequency spectrum. The Oscilloscope or the Spectrum Analyzer can be activated to view the Test Tones graphically on the Monitor screen.

The following image shows the Tones Mode display screen with Oscilloscope active:

This picture shows a 100 Hz tone in green for the left channel trace and a 500 Hz tone in blue for the right channel trace. These are pure tones since AM modulation, FM modulation, additive noise, and burst mode are all disabled, which is indicated on screen by dark gray colored readout labels at the bottom.