Headphones are personal audio devices worn over or inside the ears to deliver sound directly to the listener. They come in three primary types: Over-ear (circumaural) headphones enclose the ears with cushioned cups, offering superior noise isolation and immersive sound quality, ideal for studio use. On-ear (supra-aural) headphones rest on the outer ear, balancing portability and sound fidelity, though with less isolation. In-ear headphones (earbuds or in-ear monitors) fit inside the ear canal, providing compactness for mobile use, with options like wireless Bluetooth models (e.g., AirPods). Key features include active noise cancellation (ANC) (using microphones to counteract ambient noise), frequency response (range of audible frequencies, typically 20Hz–20kHz), and impedance (resistance affecting power needs). High-end models may support Hi-Res Audio, spatial audio, or modular cables. Applications range from music production and gaming to casual listening, with designs prioritizing comfort, durability, and sound accuracy.