It has not been known with certainty that the haddock produces underwater sounds of biological significance, though various authors have suggested the possibility.

Descriptions are given of sounds (grunts and rasp-like noises) produced in particular behavioural contexts by haddock maintained in tanks, and of sounds recorded at sea and attributed to haddock. Oscillograms and a spectrogram of these sounds are given. It is suggested that the sounds are involved in aggression and self-defence.

The sound-producing mechanism is described.