Helisagedustrafod mõjutavad helikvaliteeti, kuna need on mittelineaarsed ja lisavad algsele signaalile harmoonilisi moonutusi, eriti paaritu järjekorra harmoonilisi, rõhuasetusega kolmanda astme harmoonilistele.
Audio transformers affect the sound quality because they are non-linear, and they add harmonic distortion to the original signal, especially odd-order harmonics, with an emphasis on third-order harmonics.