The White lnstruments 155 Pink Noise Tube comes from a long line of fine instrumentation-grade noise sources manufactured over the years by White Instruments. The white noise is digitally synthesized by a random number generator operating with an extremely long word length to prevent any noticeable repetition. A precision pinking filter is applied to the white noise to create the pink noise output that is flat (±0.5dB) between 20Hz and 20kHz.