Headphones are small speakers that can be worn in or around your ears. Traditional headphones have two ear cups attached by a band that is placed over your head. Smaller headphones, often called earbuds or earphones, are placed inside the outer part of your ear canal.
Like speakers, headphones contain transducers that convert an audio signal into sound waves. Headphones that connect to an analog audio port (such as a 3.5 mm audio jack) process analog audio. Headphones that connect to a digital port, such as a USB or Lightning port process digital audio. Digital headphones must also include a digital-to-analog converter, or DAC, in order to produce the analog output.
While headphones function the same way as standalone speakers, their output is significantly different. Speakers must generate enough amplitude for the sound to be audible from far away. Headphones only need to send the sound waves a few millimeters to your ear drums. Therefore headphone components are much smaller and often more precise than speaker components. Even though the output is much lower than standalone speakers, the close proximity of headphones to your ears can make the volume sound very loud. Most headphones even support the full 20 hertz to 20,000 Hz frequency range. However, the bass is less noticeable since they don’t move as much air.
Headphones come in many shapes and sizes, but a few common types are listed below.
In-ear – earphones that fit snugly in your ear canal; typically contain rubber ends that help give them a secure fit.
Earbuds – earphones that rest inside the edge of your ear; often included with smartphones and portable media players.
On-ear – headphones that rest on your ears but don’t encompass the whole ear; helps isolate outside sounds.
Over-ear – headphones that wrap around your ears; also called “around-ear” or “circumaural” headphones; come in open and closed versions. Open versions allow all outside noise, while closed versions limit external sounds.
Noise-cancelling – creates an extra quiet listening environment by cancelling outside noise; contains a microphone that detects external sounds and sends the opposite waveform to your ear to “cancel” the noise; available in all types of form factors.