Sound was vibration that was audible to the ear.
Some lifeforms were highly sensitive to loud noise. These included the Sensorites, (TV: The Sensorites, PROSE: The Monsters from Earth) the Voord, (PROSE: The Fishmen of Kandalinga) the Ethereals in their cloud form, (PROSE: The Cloud Exiles) and the Verdants. (COMIC: Mission for Duh)
The sound of static power pulses was associated with the Daleks. (COMIC: The Only Good Dalek)
During the Dummy Massacre, (PROSE: Dummy Massacre) when the London Eye was activated by the Nestene Consciousness, (TV: Rose, PROSE: Operation Mannequin) at least one person on the Eye found themselves unable to see due to the brightness and unable to talk because of the noise. (PROSE: Dummy Massacre)
A sonic screwdriver could project sound to lock or unlock doors. (TV: The Mutants, Aliens of London)