Whispers of Terror (cassette)

In 1999, Whispers of Terror was released by Big Finish Productions.

Cover blurb
The Doctor and Peri find themselves in the Museum of Aural Antiquities, where every sound is stored for posterity. Here they can access everything from the famous speeches of Visteen Krane to security service wire taps and interrogation tapes. But they also find an intruder, mysteriously changed recordings, and a dead body.

Before long, the Doctor realises that there is more going on than a simple break-in or murder. How can he defeat a creature that is made of pure sound?