Headphones

Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which change an electrical signal into sound. Headphones let one person listen to audio privately, unlike a loudspeaker, which plays sound for everyone nearby to hear. They are also called earphones or, colloquially, cans.

Headphones connect to sources like an audio amplifier, radio, CD player, portable media player, mobile phone, video game console, or electronic musical instrument. They can connect using a cord or wireless technology such as Bluetooth, DECT, or FM radio. The first headphones were made in the late 1800s for switchboard operators so they could keep their hands free.

Headphones are used in many places and for many reasons. Starting in the 1980s, they became common in public places like sidewalks, stores, and buses because of the Walkman effect. Professionals such as audio engineers, disc jockeys, airplane pilots, and call center workers also use headphones for their jobs.

History

Headphones started when people needed a way to use the telephone without using their hands. In the 1880s, telephone operators used a device that held a telephone receiver near their ear. This helped them connect calls while keeping their hands free. At first, these devices only had one earpiece.

Later, headphones with two earpieces were made. By the early 1900s, people used headphones to listen to radio signals. Over time, headphones got better. In 1958, the first stereo headphones were created. Smaller earbuds became popular in the 1950s and 1960s with portable radios, changing how people listened to music and radio shows.

Main article: Headphones

Applications

Wired headphones work with many devices like CD and DVD players, home theater systems, personal computers, digital audio players, MP3 players, and mobile phones that have a headphone jack. Cordless headphones don’t use a cable. They get signals through radio or infrared waves using methods like FM, Bluetooth, or Wi-Fi. These are often used in places like silent discos.

In work places, headphones are important tools. DJs and sound engineers use them to listen to audio without disturbing others. Musicians and singers wear headphones in studios to hear their backing tracks. Military personnel also use headphones to listen to important audio signals. Wired headphones connect to devices using cables, with common types being 6.35 mm and 3.5 mm connectors.

Electrical characteristics

Headphones work like tiny speakers. They have special electrical properties that change how they sound. One important property is impedance. This measures how much the headphones resist the flow of electricity. Headphones can have low impedance (16 to 32 ohms) or high impedance (100 to 600 ohms). Low-impedance headphones need less power to work well. They are common in modern devices like smartphones and portable music players. High-impedance headphones need more power and work better with older audio equipment.

Another key feature is sensitivity. This tells us how well headphones turn electrical signals into sound. Sensitivity is measured in decibels. It shows how loud the headphones can get with a certain amount of power. Higher sensitivity means louder sound. It’s important not to turn the volume too high, as this can damage hearing over time. Most headphones have sensitivities between 80 and 125 dB/mW, measured at a specific frequency of 1 kHz.

Specifications

Headphones come in different sizes and styles for different needs. The main types are circumaural (over-ear), supra-aural (on-ear), earbud, and in-ear. Circumaural headphones are large and cover the ears completely. They block noise well but can be heavy. Supra-aural headphones sit on the ears. They are lighter but don’t block as much noise. Earbuds are small and fit in the outer ear. They are easy to carry but don’t block much noise and can feel uncomfortable. In-ear headphones go into the ear canal. They block out a lot of outside noise but can fall out easily.

Headphones can be open-back, semi-open, or closed-back. Open-back headphones let in more outside sound and sound more natural. Closed-back headphones block more noise and have stronger bass sounds. Some headphones are headsets. These combine a headphone with a microphone. They are useful for talking on the phone or chatting during activities like gaming or flying.

Main article: Headset (audio)

Ambient noise reduction

Unwanted sounds from around you can be reduced in two ways. The first way is called passive noise isolation. This blocks out sound by using the part of the headphone that sits over or in your ear, like an earplug. Some headphones, like in-ear and closed-back models, block more sound than others.

Another way to reduce noise is with active noise cancellation. These headphones use a microphone and a small speaker to pick up outside noise and play it back backward. This helps cancel out the unwanted sound without disturbing the music or audio you are listening to. Active noise cancelling works best on steady, low-frequency sounds, like engine noise.

Transducer technology

Headphones use different types of transducer to change electricity into sound. The most common type is the moving coil driver, often called a "dynamic" driver. It has a magnet and a coil of wire. When electricity flows through the wire, it moves and makes the diaphragm shake. This creates sound waves.

Other types include MEMS speakers, which are made on tiny chips. There are also electrostatic drivers, which use a thin charged diaphragm to make sound. Electret drivers have a permanent charge, and planar magnetic drivers use a large membrane with wires to produce sound. Each type works in its own way to make audio.

Benefits and limitations

Headphones let you listen to music or other sounds by yourself without disturbing others, like in a quiet library. They can also give better sound quality than regular speakers, especially for low-pitched sounds, because they sit close to your ear and don’t need to push a lot of air.

Headphones are great for video games because they help you hear where sounds are coming from, like the footsteps of someone behind you. While many headphones are made for regular music listening, some special kinds, called binaural recordings, can make sounds feel very real when you wear them. Headsets can also help people who spend long times on the phone stay more comfortable by letting them talk without holding the phone to their ear.

Health and safety

See also: Automatic volume limiter

Dangers and risks

Using headphones at high volume can hurt your hearing. This is especially true in loud places like subways or airplanes, where you might turn the music up too loud. Experts suggest not listening to music louder than 80 decibels for more than 40 hours a week to protect your ears. Many smartphones have features to help limit volume.

Headphones can also be distracting, especially when you're driving or cycling. Some places have rules against using headphones while doing these activities. There have been some reports of skin irritation from in-ear headphones.

Occupational health and safety

Workers who use headphones or headsets for their jobs, like pilots or call center operators, also need to be careful about volume. Long periods of loud sounds can damage hearing. Guidelines suggest keeping sound levels below 85 decibels during an 8-hour workday. If the volume is higher, the time you can safely listen should be shorter.