Hum Audio noise that has a steady low-frequency pitch, typically caused by the effects of induction of nearby AC lines or leakage of AC line frequency into an amplifier’s signal circuits, usually at 60Hz or 120Hz. Share this:EmailTweetLike this:Like Loading...Related Articles: Glossary: Comb filterGlossary: Common modeGlossary: Ground loopGlossary: Hum switchGlossary: Mastering« Back to Glossary Index