Muzak was coming from invisible speakers on the ceiling.

Harry nodded, even though he could not see the invisible speaker.

"HandphoneTable," of 1978-79, is a simple hollow table fitted with invisible speakers.

He threw the coat at the invisible speakers, scrabbled for something heavier.

The invisible speaker appeared to give this some consideration.

He tilts his head up as if listening to an invisible speaker.

"On the contrary," Hector's voice replied from invisible, overhead speakers.

Par Leon jerked his head toward an invisible speaker.

Floating through the invisible speakers, Landon's voice filled the room.

But still another had witnessed everything: the invisible speaker.