Using the Tone Generator

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PassMark SoundCheck includes a tone generator, which can be used to create test tones that can be outputted to the sound card or saved to a wav file. To open the tone generator select Create Tone from the menu. From this window it is possible to enter the Wave shape, the wave amplitude and the frequency of the wave. The output of the tone generator will also be affected by the sound format, which was selected from the main window. Thus if a sample rate of 44KHz was selected, this will also be used by the tone generator.

To use the tone generator effectively you need to understand the difference between sampling rate and frequency as well as other concepts related to the reproduction of sound. See the digital sound page for more details.

In the frequency domain, the range of human hearing is between approximately 20 to 20,000 Hz, so don’t expect to hear very much if sound you generate is outside of this range. With age hearing become less sensitive, maybe as low as 13KHz at 65years. There is also some variability according to sex with women typically having sensitivity to higher frequencies than men. The human ear is most sensitive around 3000Hz. Even if you have perfect hearing your speakers may not be able to reproduce higher or lower frequencies with any accuracy.

It is only possible to generate frequencies up to half of the current sampling rate. This is due to the Nyquist theory, named after the Bell engineer Harry Nyquist, who worked on the speed of telegraphs in the 1920s. Nyquist theory states that a waveform must be sampled at least twice in order to get a true representation. Thus a regular CD sampled at 44.1 kHz is theoretically capable of reproducing frequencies up to 22 kHz. If you try to generate a frequency above this limit, the resulting waveform will not have the correct frequency or shape.

Wave shape

The follow wave form shapes can be selected. Sine wave, Saw tooth wave, Square wave, Spikes and White noise. White noise is not strictly speaking a ‘shape’, but rather it is random noise spread out evenly across the available spectrum.

Amplitude

This value determines the loudness of the sound. A value of 100 means that a full height wave will be created. A value of 0 will create a wave that has no height (and no volume). The final loudness of the output will be determined by this value, the position of the volume dial on your speakers and the settings in the mixer.

Frequency

This is the frequency of the waveform. It is the number of waves that occur per second. This value is not used for white noise, which has no particular frequency. See the comments at the top of this page for frequency limitations and the digital sound page for more information about sound concepts. The maximum frequency that can be accurately generated is equal to half of the current sampling rate. High sampling rate mean more faithful sound reproduction but they also take up more system resources to sample and store.

Seconds

Only applicable when saving a tone to a wave file. This value specifies the minimum length the output wave file should be by repeating the tone. Usually the output will match this number of seconds however in some cases, especially when using low sample rates, it may be a few seconds longer.

Note:

The Tone Generator is particularly useful with loopback testing as the waveforms are easily analysed for distortion and noise.