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The TPDF Noise Module provides sources of white and blue noise with selectable Probability Density Functions (PDFs).
It was designed to be used as a source of Triangular Probability Density Function white noise for dithering purposes in the Bit Reducer Module. Uncorrelated stereo TPDF noise can be generated by running two instances of the module in parallel – one providing noise for the left channel and one for the right channel.
The White noise output can be switched between Rectangular PDF (to the left), and Triangular PDF (to the right, default). White noise has a flat frequency response across the entire audio spectrum. If RPDF white noise is used as input to a Sample & Hold module, the random output voltages will have equal probability within the range -5V to +5V. If TPDF white noise is used instead, there is much higher probability that the random output voltages will be close to 0V, and lower probability of being close to the +/-5V extremes.
The Blue noise output can be switched between Triangular PDF (to the left), and Gaussian PDF (to the right, default). Blue noise has greater energy towards the upper end of the audio spectrum, and thus provides a rudimentary form of perceptual ‘noise shaping’ when used as a dithering source. Gaussian PDF noise has an even greater tendency towards 0V output than Triangular PDF, although there is still a finite probability of experiencing voltage outputs very close to +/-5V.