The outer shells of in-ear headphones are made up of a variety of materials, such as plastic, aluminum, ceramic and other metal alloys. Because in-ear headphones engage the ear canal, they can be prone to sliding out, and they block out much environmental noise. Lack of sound from the environment can be a problem when sound is a necessary cue for safety or other reasons, as when walking, driving, or riding near or in vehicular traffic.
Again, back on the automobile analogy. If you’re driving in downtown Chicago after winter time, the road is full of potholes. It would be nice to be riding in a nice SUV, rather than typical sports car with a fully stiff suspension. It doesn’t matter if your sports car happen to cost three times the cost of the SUV, it’s just the wrong car for the road. Likewise headphones. A $1,000 headphone can sound very awful on the wrong music. Don’t believe me? Try listening to Linkin Park with the $1,800 Sennheiser HD800. You will wonder where that $1,800 went.
Active noise-cancelling headphones use a microphone, amplifier, and speaker to pick up, amplify, and play ambient noise in phase-reversed form; this to some extent cancels out unwanted noise from the environment without affecting the desired sound source, which is not picked up and reversed by the microphone. They require a power source, usually a battery, to drive their circuitry. Active noise cancelling headphones can attenuate ambient noise by 20 dB or more, but the active circuitry is mainly effective on constant sounds and at lower frequencies, rather than sharp sounds and voices. Some noise cancelling headphones are designed mainly to reduce low-frequency engine and travel noise in aircraft, trains, and automobiles, and are less effective in environments with other types of noise.
What I’m saying here is that it’s better to own three $100 headphones than one $300 headphone. Or three $300 headphones than one $900 headphone. Why? Because most people don’t limit their playlist to strictly one genre. And following the logic from Rule #2, the right headphone-music pairing is going to be better than one expensive headphone paired to the wrong music.
Supra-aural headphones or on-ear headphones have pads that press against the ears, rather than around them. They were commonly bundled with personal stereos during the 1980s. This type of headphone generally tends to be smaller and lighter than circumaural headphones, resulting in less attenuation of outside noise. Supra-aural headphones can also lead to discomfort due to the pressure on the ear as compared to circumaural headphones that sit around the ear. Comfort may vary due to the earcup material.
Although some headphones available are wired, many more are available that are wireless, and use Bluetooth to enable your music to be heard, even if the stereo or other device is several feet or even a few rooms away. Wired headphones deliver superior sound quality to wireless and Bluetooth because there's no chance of picking up interference from other devices, which sometimes happens with wireless headphones. In addition, wired headphones have no batteries to power them, so there's no chance of interruption should the batteries wear out.