White-sound device
The white-sound device in use
A white-sound device was an instrument in use aboard Starfleet vessels that was able to mask individual sounds from sensor devices.
It was employed on the bridge of the USS Enterprise in the year 2267, during testimony in the court martial of Captain James T. Kirk. Doctor Leonard McCoy used the device to mask the sound of the remaining crew members' and court personnel's heartbeats. This allowed the sensors to detect Lieutenant Commander Benjamin Finney's heartbeat; Finney was previously thought to have died due to Kirk's actions, thereby prompting the court proceedings.
Finney was ultimately located in engineering. (TOS: "Court Martial")