Headphones are familiar to virtually everyone but professional-quality DJ headphones and studio headphones are on an entirely different level from those made for the average listener. These high-end designs are built to deliver better performance in the most important metrics such as SNR (signal-to-noise ratio) which describes the clarity of the sound and the frequency response range which is the window of frequencies from lowest to highest that the headphones are capable of reproducing. In many ways the output specifications of headphones resemble the input specs of microphones - small wonder then that many of the leading brands are also known for mics including Audio-Technica Beyerdynamic Sennheiser and Shure.
Headphones are often built for specific applications such as studio monitors broadcast headsets or audiophile listening. This has given rise to a variety of styles each specialized for certain uses. For instance, closed-back headphones and isolation headphones are designed to cancel out background noise for a pure rendering of the sound. Open-back headphones by contrast allow ambient noise to enter which is useful for artists wanting to hear how their music might sound when played back in noisy places. For any of these pro headphone styles getting the best results depends on the provision of adequate power. This generally requires the use of a headphone amplifier or at the very least equipment with headphone amplification already built in.