Metric Halo SpectraFoo - Manual (Page 92)

Signal Generator
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5. Duration edit-text box: The Duration is the period of time that will elapse between the start and end
of the sweep.
6. Post-Delay edit-text box: The Post-Delay time is the period of time that will elapse after the end of the
sweep before the sweep loops around.
Additive pink noise with sweepable level
The signal generator also provides additive pink noise. The pink noise generated by SpectraFoo is 1/f noise
with a low frequency roll-off. This means that above 30Hz the frequency distribution of the noise has equal-
power per octave. The controls for the pink noise generator are:
Figure 8.5: Pink Noise Parameter Cluster
1. Enable checkbox: Checking this turns on the additive white noise.
2. Start Level edit-text box: The peak level of the white noise at the start of the sweep. This level is in units
of dBFS and may be positive or negative.
3. End Level edit-text box: The level entered into this box is used as the ending level of the sweep. This
level is in units of dBFS and may be positive or negative. An entry of “*” means “use the start value”.
4. Pre-Delay edit-text box: The Pre-Delay time is the period of time that will elapse before the sweep starts.
5. Duration edit-text box: The Duration is the period of time that will elapse between the start and end
of the sweep.
6. Post-Delay edit-text box: The Post-Delay time is the period of time that will elapse after the end of the
sweep before the sweep loops around.
Dither & Quantization
You can control the quantization and dither used by the signal generator in the generation of the signals. The
generator provides for quantization from 2 bits per sample to 24 bits per sample. Quantization is always active
and the signal will be truncated to the number of bits specified in the Sample Size edit-text box:
Figure 8.6: Quantization and Dither controls
When the Dither button is checked, the signal generator will dither the signal before truncation. Dithering
replaces distortion with uncorrelated noise. The dither in SpectraFoo is noise shaped which causes the noise
floor to decrease with decreasing frequency. This has the effect of decreasing the noise where it is most audible
while still removing the distortion caused by quantization.