Headphones are wearable, stereo, miniaturized speaker systems.
Traditional headphones were quite large and bulky, consisting of a left and right speaker contained in padded ovular enclosures called ear cups. The cups were attached to an arching headband that supported a connecting left-right speaker wire. Trailing off each ear cup was a left or right channel signal wire, joined at a junction to form a single stereo cable with connector. The connector plugged into a headphone jack.
Today headphones have come a long way from the bulky sets of yesteryear. Lightweight, portable headphones, called earbuds, are nearly unnoticeable. Rather than the old headband, these tiny speakers sit inside the opening of the ear itself. Wiring is much thinner and more flexible, allowing for a more comfortable, pleasurable experience.
There are several types of headphones available today for every purpose. The vast majority of headphones sold to the general public are used with hi-tech gadgets such as personal audio players. Cell phones can also be used with a headset that consists of a single mono earbud and miniature microphone. The headset plugs into the phone to allow hands-free operation of the phone.
There are two main styles of earbud headphones for stereo use: those that freely sit in the ear; and those that have a small flexible arm that wraps over the ear to hold the bud in place. The latter style is great for active use, such as jogging, boarding, skating or skiing. The former is convenient for quiet activities like walking or home use. Earbud headphones are very inexpensive with a decent pair costing as little as $10 (US dollars).
The advantage of earbud headphones for personal activities is that one can enjoy high fidelity while retaining a certain amount of audible awareness of the immediate environment. The earbuds do not block out all external sound, so that the wearer can be conscious of things like traffic or other people.
However, for those who want to use headphones in a noisy environment, it may be desirable to block out some of this external noise. In this case sound isolating or noise cancelling headphones may be desirable.
Some noise canceling headphones use earbuds with foam or plastic sleeves to fit inside the ear, like earplugs. This design passively and indiscriminately blocks most external noise. Another style uses ear cups fitted with an external microphone to sample surrounding noise. Based on the sample, the headphones generate mirror-image waves to cancel out undesirable noise discriminately. This is handy in an environment like a subway, where one wants to block mechanical noise and drone, yet hear conductor announcements that will pass through the sound canceling barrier. A disadvantage of these headphones is that they are battery operated. They also tend to be expensive.
Another innovation is wireless headphones, which use a transmitter base to relay signals to the headset, eliminating the need for wires. This frees up the wearer, for example, to traverse the house while listening to the entertainment center.
Finally, traditional style, high quality headphones for professional use in recording studios and musical environments are also available. These will use ear cups to block competing noise.
Fidelity varies greatly among headphones. Some sets will stress bass, but too much bass without sufficient mid and high range frequencies will make for a muddy sound. More commonly, headphones can lack bass, but a decent pair of headphones will deliver high-quality, satisfactory sound.