The speaker was a type of communications device used for converting electric signals into audible sound. Speakers were built for an audience in mind. Speakers could be found in starships.
In 2286, aboard the HMS Bounty, James T. Kirk requested that the message being transmitted to Earth by the Whale Probe be placed on speakers by the communications officer Nyota Uhura. Later, after successfully traveling back in time to 1986 Earth, Kirk again asked Uhura to put a transmission on speakers. This transmission was of a whale song that was being sung by George and Gracie at their home in the Cetacean Institute. (Star Trek IV: The Voyage Home)