Headphones are a pair of small loudspeakers, or less commonly a single speaker, with a way of holding them close to a user’s ears and a means of connecting the head phones to a signal source such as an audio amplifier, radio or CD player. Headphones are also known as earphones, earbuds, stereophones, headsets or, colloquially cans.
In the context of telecommunication, the term headset is used to describe a combination of headphone and microphone used for two-way communication, for example with a telephone.
Private investigators may use headphones during the course of a surveillance mission, especially in relation to the use of audio surveillance equipment and listening devices. Private investigators often need to listen to conversations from a distance, so electronic listening devices and headphones are often used.