All the while, a small, hidden speaker played sections of the sound archives in which women's voices could be heard. (projectspacefestival-berlin.com)
The music is all choral music played from hidden speakers, with many of the pieces performed by the Salisbury Cathedral Choir. (treehugger.com)
These manufactured altercations — for example, playing a threat vocalization by a high - ranking female followed by the submission squeal of a lower - ranking animal — were then played through hidden speakers while the scientists recorded the reactions of listening baboons. (scientificamerican.com)