The Soundproof Witness by AJ Archibald

A renowned acoustics expert dies inside a room engineered to hear nothing. The door is locked. The access log shows he was alone. Yet his final call insists the room is not empty.

Forensic audio restorer Lena Hart is summoned to Larkspur Hall, where hidden speakers whisper private accusations and every suspect has heard the dead man confess a different secret. Beneath the concert hall, a forgotten lift, an unfinished concerto, and a recorder that listens through stone connect the murder to a death concealed eighteen years earlier.

With Detective Owen Mercer and Deaf restoration architect Amara Singh, Lena must separate live voices from planted evidence before the killer turns the entire building into an alibi. Because in a hall designed to remember everything, the most dangerous clue is the silence someone carefully arranged.