Headphones

WHAT IS HEDAPHONES?

Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear.

WHEN HAS IT EMERGED?

By the 1890s the first device that is unmistakably a headphone was made by a British company called Electrophone, which created a system allowing their customers to connect into live feeds of performances at theaters and opera houses across London. Subscribers to the service could listen to the performance through a pair of massive earphones that connected below the chin, held by a long rod. French engineer Ernest Mercadier patented a set of in-ear headphones in 1891, Mercadier was awarded U.S. Patent No. 454,138 for “improvements in telephone-receivers…which shall be light enough to be carried while in use on the head of the operator.

Headphones originated from the telephone receiver earpiece and were the only way to listen to electrical audio signals before amplifiers were developed. These early headphones used moving iron drivers, with either single-ended or balanced armatures. The common single-ended type used voice coils wound around the poles of a permanent magnet, which were positioned close to a flexible steel diaphragm. The audio current through the coils varied the magnetic field of the magnet, exerting a varying force on the diaphragm, causing it to vibrate, creating sound waves. The requirement for high sensitivity meant that no damping was used, so the frequency response of the diaphragm had large peaks due to resonance, resulting in poor sound quality. These early models lacked padding and were often uncomfortable to wear for long periods. Their impedance varied; headphones used in telegraph and telephone work had an impedance of 75 ohms. Those used with early wireless radio had more turns of finer wire to increase sensitivity.

Impedance of 1,000 to 2,000 ohms was common, which suited both crystal sets and triode receivers. Some very sensitive headphones, such as those manufactured by Brandes around 1919, were commonly used for early radio work. In early powered radios, the headphone was part of the vacuum tube's plate circuit and carried dangerous voltages. It was normally connected directly to the positive high voltage battery terminal, and the other battery terminal was securely grounded. The use of bare electrical connections meant that users could be shocked if they touched the bare headphone connections while adjusting an uncomfortable headset. In 1958, John C. Koss, an audiophile and jazz musician from Milwaukee, produced the first stereo headphones.

Previously, headphones were used only by the US navy, telephone and radio operators, and individuals in similar industries. Smaller earbud type earpieces, which plugged into the user's ear canal, were first developed for hearing aids. They became widely used with transistor radios, which commercially appeared in 1954 with the introduction of the Regency TR-1. The most popular audio device in history, the transistor radio changed listening habits, allowing people to listen to radio anywhere. The 3.5 mm radio and phone connector, which is the most commonly used in portable application today, has been used at least since the Sony EFM-117J transistor radio, which was released in 1964.Its popularity was reinforced with its use on the Walkman portable tape player in 1979.

Since the early days of the transistor radio, earphones have commonly been bundled with personal music devices. The use of the term earbuds, which has been around since at least 1984, did not hit its peak until after 2001, with the success of Apple's MP3 player.

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