Howling or oscillation in an in-vehicle communications system is prevented when the speaker gain or microphone gain is detected as giving rise to a loop gain equal to or greater than one for a particular frequency or band of frequencies or when the rate of gain of a frequency or band of frequencies increases at a rate that indicating howling will occur. Howling is prevented and not just stopped or suppressed, by adjusting the gain of all frequencies prior to the howling actually starting.