Relay noise in audio applications can be a frustrating issue that injects disruptive electrical noise into your sound signal. This noise typically occurs when electromechanical switches activate or deactivate, causing sudden changes in current flow that couple into sensitive audio circuits. While relays are useful for switching high-power signals, their moving contacts makes them likely to produce electromagnetic bursts.

To reduce relay-induced interference, start by selecting an appropriate relay technology. Solid state relays are often a better option for audio because they have no physical contacts and operate silently, preventing disruptive surges. If you must use a mechanical relay, select one with a minimized coil inductance and consider using a RC snubber—a passive R-C filter—across the relay coil to suppress reverse voltage spikes generated during switching.

Additionally, ensure effective earth bonding and EMI containment. Keep relay power and control lines away from sensitive audio traces and use braided shield cables where possible to reduce RF coupling. Place the relay as far as practical from high-gain audio circuits, and consider adding a small ferrite bead on the relay power line to block switching harmonics.

Power supply filtering is also essential. Use decoupling capacitors near the relay’s power input and consider a separate low-noise supply for the audio section. Finally, implement digital timing delays if the relay is driven by a microcontroller, so that switching happens during periods of no audio activity.

By combining these techniques—choosing low-noise switching technology, filtering transients, physically separating noise sources, and delaying activation to silent moments—you can virtually remove audible interference and maintain clean, professional audio quality.