signal can be reduced and focused only on the problematic frequencies. The differences in the various Dolby products are largely in the precise set of frequencies that they use and the amount of modification of the original signal volume that is applied to each of the frequency bands.

Within each band, the amount of pre-emphasis applied depends on the original signal volume. For instance, in Dolby B, a low-level signal will be boosted by 10 dB, while signals at the "Dolby Level", +3 VU,