Headphones (or head-phones in the early days of phone and radio) are a pair of small loudspeaker drivers worn on or around the head above the user's ear. They are electroacoustic transducers, which convert electrical signals into appropriate sound. Headphones allow a single user to listen to the audio source personally, unlike the loudspeaker, which emits sound to the open air for anyone close to hear. Headphones are also known as loudspeakers, earphones or, everyday language, cans . The circumaural and supra-aural headphones use the tape above the head to hold the speakers in place. The other type, known as earbud or earpiece consists of individual units connected to the user's ear canal. In the context of telecommunications, a headset is a combination of headphones and a microphone. Headphones are connected to signal sources such as audio amplifiers, radios, CD players, portable media players, mobile phones, video game consoles, or electronic instruments, either directly using cables, or using wireless technologies such as Bluetooth, DECT or FM radio. The first headphones were developed in the late 19th century for use by phone operators, to keep their hands free. Initially the audio quality is mediocre and the step forward is the discovery of high fidelity headphones.
Headphones are made in different audio quality reproduction capabilities. Headsets designed for phone use are typically unable to reproduce sound with high fidelity from expensive units designed to listen to music by audiophiles. Headphones using cables typically have a 1/4 inch (6.35 mm) or 1/8 inch (3.5 mm) phone jack to plug the headphones into an audio source. Some stereo earbuds are wireless, using Bluetooth connectivity to transmit audio signals by radio waves from source devices such as mobile phones and digital players. Due to the deployment of wireless devices in recent years, headphones are increasingly being used by people in public places such as sidewalks, grocery stores, and public transport. Headphones are also used by people in various professional contexts, such as audio mixing engineers for live concerts or sound recording and DJs, who use headphones to direct the next song without audience audience, aircraft pilots and call center employees. The latter two types of employees use headphones with an integrated microphone.
Video Headphones
Histori
The headphones come from the earpiece of the telephone receiver, and are the only way to listen to the electrical audio signal before the amplifier is developed. The first truly successful device was developed in 1910 by Nathaniel Baldwin, who made it by hand in his kitchen and sold it to the United States Navy.
These early headphones use a movable iron driver, either with a single or end arms. The commonly used single-ended type of circular sound coils around a permanent magnetic pole, which is positioned close to a flexible steel diaphragm. The audio currents through the windings vary magnetic field magnets, exert varying forces on the diaphragm, causing it to vibrate, creating sound waves. The requirement for high sensitivity means that no damping is used, so the frequency response of the diaphragm has a large peak due to resonance, resulting in poor sound quality. This initial model has no pads, and is often uncomfortable for a long time. The impedance varies; headphones used in telegraph and phone work have 75 ohms impedance. Used with early wireless radios have more fine wire spin to increase sensitivity. Impedance 1000 to 2000 ohm is common, suitable for crystal sets and triode receivers. Some highly sensitive headphones, such as those manufactured by Brandes around 1919, are commonly used for early radio work.
In early-powered radios, headphones are part of the vacuum tube plate circuit and carry dangerous voltages. It is usually connected directly to the positive high voltage battery terminals, and other battery terminals are safely earthed. The use of bare electrical connections means that users can be surprised if they touch the naked headphone connection while adjusting the uncomfortable headset.
In 1958, John C. Koss, an audiophile and jazz musician from Milwaukee, produced the first stereo headphones. Previously, headphones were only used by US naval, telephone, and radio operators, and individuals in similar industries.
The smaller earbud earpiece, plugged into the user's ear canal, was first developed for hearing aids. They became widely used with transistor radios, which commercially emerged in 1954 with the introduction of the TR-1 District. The most popular audio devices in history, transistor radios changing listening habits, allowing people to listen to the radio on the go. Earbuds use moving iron drivers or piezoelectric crystals to produce sound. The 3.5 mm radio and telephone connectors, most commonly used in portable applications today, have been used since at least the EFM-117J transistor radio, released in 1964. Its popularity is reinforced with its use on the Walkman. portable tape player in 1979.
Maps Headphones
Apps
Headphones can be used with stationary CD and DVD players, home theater, personal computers, or portable devices (eg, digital audio players/MP3 players, mobile phones). The cordless headphones are not connected to the source by cable. Instead, they receive radio or infrared signals that are encoded using radio or infrared transmission connections, such as FM, Bluetooth or Wi-Fi. It is a powered receiver system, where headphones are just components. The cordless headphones are used with events such as Silent disco or Silent Gig.
In the professional audio sector, headphones are used in direct situations by disc jockeys with DJ mixers, and sound engineers to monitor signal sources. In the radio studio, the DJ uses a pair of headphones while talking with a microphone while the speakers are turned off to remove acoustic feedback while monitoring their own voice. In the studio recording, musicians and singers use headphones to play or sing along to a support track or band. In military applications, audio signals from many varieties are monitored using headphones.
The wired headphones are plugged into the audio source by cable. The most common connectors are 6.35 mm (¼?) And 3.5 mm telephone connectors. The larger 6.35 mm connector is more commonly used in home or professional equipment at a fixed location. The 3.5 mm connector remains the most widely used connector for today's portable applications. The adapter is available to convert between 6.35 mm and 3.5 mm devices.
Electrical characteristics
The dynamic electrical characteristics of the loudspeakers can be directly applied to the headphones, as most headphones are small dynamic speakers.
Impedance
Headphones are available with low or high impedance (usually measured at 1 kHz). Headphones with low impedance are in the range of 16 to 32 ohm and high-impedance headphones around 100-600 ohms. When the impedance of a pair of headphones increases, more voltage (at the specified current) is required to drive it, and the loudness of the headphones for a given voltage decreases. In recent years, newer headphone impedances have generally declined to accommodate the lower voltages available on CMOS-based portable electronic devices that use battery power. It has produced headphones that can be more efficiently driven by battery powered electronics. As a result, newer amplifiers are based on designs with relatively low output impedances.
The headphone impedance is a concern because of the limited output of the amplifier. A pair of modern headphones are powered by an amplifier, with low impedance headphones presenting a larger load. Amplifier is not ideal; they also have some output impedance which limits the amount of power they can provide. To ensure the frequency response, adequate damping factor, and undistorted sound, the amplifier must have an output impedance of less than 1/8 of the headphones being ridden (and ideally, as low as possible). If the output impedance is large compared to the headphone impedance, there is a significantly higher distortion. Therefore, lower-impedance headphones tend to be louder and more efficient, but also require more qualified amplifiers. Higher impedance headphones are more tolerant of limitations of the amplifier, but produce less volume for given output levels.
Historically, many headphones have a relatively high impedance, often more than 500 ohms so they can operate well with high impedance tube amplifiers. In contrast, modern transistor amplifiers can have very low output impedances, allowing headphones with lower impedances. Unfortunately, this means that older audio amplifiers or stereos often produce low-quality output on some modern, low-impedance headphones. In this case, an external headphone amplifier may be useful.
Sensitivity
Sensitivity is a measure of how effectively the earpiece converts the incoming electrical signal into audible sound. Thus indicating how hard the headphones for the level of electric drive is given. This can be measured in decibels of sound pressure level per milliwatt (dB (SPL)/mW) or decibels sound pressure level per volt (dB (SPL)/V). Unfortunately, these two definitions are widely used, often interchangeably. Since the output voltage (but not the power) of the headphone amplifier is essentially constant for the most common headphones, dB/mW is often more useful if converted to dB/V using Ohm's law:
Alternatively, the online calculator can be used. Once the sensitivity per volt is known, the maximum volume for a pair of headphones can be easily calculated from the maximum amplifier output voltage. For example, for headphones with a sensitivity of 100 dB (SPL)/V, the amplifier with an average 1-output mean root (RMS) produces a maximum volume of 100 dB.
Pairing headphones with high sensitivity with the power amplifier can produce very high volume and damage the headphones. The maximum sound pressure level is a matter of preference, with some sources recommending no higher than 110 to 120 dB. In contrast, the American Occupational Safety and Health Administration recommends an average SPL of no more than 85 dB (A) to avoid long-term hearing loss, while EU EN 50332-1: 2013 recommends that volumes above 85 dB (A) include warnings , with absolute maximum volume (defined using 40-4000 Hz sounds) not more than 100 dB to avoid accidental hearing damage. Using this standard, headphones with sensitivity of 90, 100 and 110 dB (SPL)/V should be driven by amplifiers capable of not more than 3,162, 1.0 and 0.3162 RMS volts at maximum volume settings, respectively to reduce the risk of hearing loss.
Headphone sensitivity is typically between about 80 and 125 dB/mW and is usually measured at 1 kHz.
Type
Headphone size can affect the balance between loyalty and portability. In general, the headphone form factor can be divided into four separate categories: circumaural (excessive ear) , supra-aural (ear) , earbud > and ear-in .
Circumaural
Circular headphones (sometimes called full-size headphones or over-ear headphones) have circular or elipsoid earpads that cover the ears. Because these headphones actually surround the ears, the circumaural headphones can be designed to cover the head completely to reduce external noise. Due to its size, circumaural headphones can be heavy and there are several sets that weigh more than 500 grams (1 pound). Ergonomic headgear and ear design is needed to reduce discomfort due to weight. This is usually used by drummers in the recording.
Supra-aural
Supra-aural headphones or headphones in the ear have pads that push the ears, not around them. They are generally bundled with personal stereos during the 1980s. These type of headphones generally tend to be smaller and lighter than the circumaural headphones, thus reducing the noise outside. Supra-aural headphones can also cause discomfort due to pressure on the ear compared to the circumaural headphones that sit around the ear. Comfort can vary due to earcup material.
Open or close again
The circumaural and supra-aural headphones can be more distinguished by the type of earcup:
Headphones Open-back have the back of the earcup open. It removes more sound from headphones and also allows more ambient sound to the headphones, but it gives a more natural sound or like speakers, as it includes sound from the environment.
The Closed-backed (or sealed) style has the back of the closed earmuffs. They usually block some ambient noise. Closed headphones can usually produce a lower frequency that is stronger than an open-back headphone.
Headphones Semi-open , has a design that can be considered as a compromise between open-back headphones and closed headphones. Some believe that the term "semi-open" is purely there for marketing purposes. There is no definitive definition for semi-open headphones. Where the open-back approach has almost no size to block sound on the outer side of the diaphragm and the closed-back approach actually has a closed space on the outer side of the diaphragm, semi-open headphones can have room for a partial block of sound while allowing some sound through through the opening or ventilation.
Headphones that fit the ear
Earphone
The earphone is a very small headphone mounted directly on the outer ear, facing but not inserted into the ear canal. Earphones are portable and comfortable, but many people find them uncomfortable. They barely provide acoustic isolation and leave room for ambient noise to permeate; the user can raise a very high volume to be compensated, with the risk of causing hearing loss. On the other hand, they let users be more aware about their environment. Since the early days of transistor radios, earphones are generally bundled with personal music devices. They are sold at times with foam pads for convenience. (The use of the term In-ear headphones
In-ear headphones, also known as in-ear monitors (IEMs) or canalphones, are small headphones with similar portability to earbuds inserted into the ear canal itself. IEMs are high quality in-ear headphones and are used by audio engineers and musicians as well as audiophiles.
The outer in-ear headphones are made up of various materials, such as plastic, aluminum, ceramics and other metal alloys. Because in-ear headphones involve the ear canal, they can easily slide out, and they block out a lot of environmental noise. Lack of noise from the environment can be a problem when sound is a signal needed for safety or other reasons, such as when walking, driving, or riding near or in vehicle traffic.
Generic or custom-pass ear plugs are made of silicone rubber, elastomers, or foams. Custom in-ear headphones use castings from the ear canal to create custom-molded plugs that provide added comfort and sound insulation.
Paired pasphone earphones
This type combines the advantages of earbuds and in-ear headphones - depending on the environment and user requirements, they provide passive noise reduction for quality mode (conversation or active music listening) or they provide control over the surround sound environment in the standby or standby mode. background sound/listening music).
Headset
A headset is a headphone combined with a microphone. The headset provides an equivalent function of the phone handsets with hands-free operation. Among the applications for headsets, in addition to telephone use, are aviation, theater or television studio intercom systems, and consoles or PC games. The headset is made with a single earpiece (mono) or double earpiece (mono for both ears or stereo). The headset microphone arm is an external microphone type where the microphone is held in front of the user's mouth, or the voicetube type where the microphone is placed in the earpiece and the utterance reaches with a vacuum tube.
Phone headset
The telephone headset is connected to a fixed-line telephone system. The phone headset works by changing the handset of the phone. The headset for a standard wired phone is equipped with a standard 4P4C commonly called the RJ-9 connector. The headset is also available with 2.5 mm jack sockets for many DECT phones and other applications. A cordless bluetooth headset is available, and is often used with cell phones. Headsets are widely used for telephone intensive work, especially by call center workers. They are also used by anyone who wants to hold a phone conversation with both hands free.
For older phone models, the headset microphone impedance is different from the original phone, requiring phone amplifier for the phone headset. A phone amplifier provides basic pin settings similar to a telephone headset adapter, but also offers voice amplification for microphones and speakers. Most models of phone amplifiers offer volume control for the loudspeaker as well as a microphone, mute function and switch between headset and handset. The phone amplifier is powered by a battery or AC adapter.
Ambient noise reduction
Unwanted noise from the environment can be reduced by sounding from the ear with passive sound insulation, or, often simultaneously with isolation, by active noise cancellation.
Passive noise insulation essentially uses the earphone body, either above or in the ear, as a passive earplug that only blocks sound. The type of headphones that provide the most attenuation is the headphones of the canal inside the ear and the closed headphones, both circumaural and supra aural. The open-back and earbud headphones provide some passive sound insulation, but much less than others. Typical closed headphones block out 8 to 12 dB, and in-ear anywhere from 10 to 15 dB. Some models have been specially designed for the drummer to allow the drummer to monitor recorded sounds while reducing the direct sound from the drum as much as possible. Headphones like this are claimed to reduce noise around 25dB.
Active noise-canceling headphones use microphones, amplifiers, and speakers to take, amplify, and play ambient sounds in reversed-phase; this to some extent undo the unwanted sound from the environment without affecting the desired sound source, which is not taken and reversed by the microphone. They need resources, usually batteries, to drive their circuits. Active noise cancelling headphones can reduce ambient noise by 20 dB or more, but active circuits are especially effective at constant noise and at lower frequencies, rather than sound and sharp sound. Some noise-suppression headphones are designed primarily to reduce low-frequency engines and travel noise on airplanes, trains and cars, and are less effective in environments with other types of noise.
Transducer technology
Headphones use different types of transducers to convert electrical signals into sound.
Move-coil
Moving coil movers, more commonly referred to as "dynamic" drivers are the most commonly used types of headphones. It consists of a stationary magnetic element affixed to the headphone frame, which forms a static magnetic field. Magnets in headphones usually consist of ferrite or neodymium. Sound coils, light wire coils, suspended in magnetic magnetic fields, attached to the diaphragm, are usually made of light, high-stiffness-to-mass-ratio of cellulose, polymer, carbonaceous material, paper or the like. When the current varies from the audio signal passed through the coil, it creates a varying magnetic field that reacts to the static magnetic field, exerting different forces on the coil causing it and the apertured attached diaphragm. The vibrating diaphragm pushes in the air to produce sound waves.
Electrostatic
The electrostatic driver consists of a thin, electrically charged diaphragm, usually a coated PET film membrane, suspended between two perforated metal plates (electrodes). An electric sound signal applied to the electrode creates an electric field; depending on the polarity of this field, the diaphragm is pulled towards one of the plates. Air is forced through perforation; combined with the constantly changing electrical signals driving the membrane, sound waves are generated. The electrostatic headphone is usually more expensive than the coil-moving, and is relatively rare. In addition, a special amplifier is required to amplify the signal to deflect the membrane, which often requires an electrical potential in the range of 100 to 1000 volts.
Because the membrane diaphragm is very thin and light, often just a few micrometers thick, and in the absence of moving metal, the frequency response of electrostatic headphones usually extends well above the audible limit of about 20 kHz. High frequency response means that a low level of midband distortion is maintained at the top of the audible frequency band, which is generally not the case with movable moving coils. Also, frequency responses are regularly visible in high frequency areas with no moving coil drivers. Well-designed electrostatic headphones can produce much better sound quality than any other type.
Electrostatic headphones require a voltage source that produces 100 V to more than 1 kV, and is in the user's head. Since the invention of the isolator, there is no real danger. They do not need to provide a significant electrical current, which further limits the electrical hazard to the wearer in the event of an error.
Electret
Electrical drivers function along the same electromechanical means as electrostatic drivers. However the electret driver has a permanent charge built in it, while the electrostatic has a charge applied to the driver by an external generator. Electrons and electrostatic headphones are relatively uncommon. Authentic originals are also usually cheaper and lower in technical capability and precision than electrostatic. The patent application from 2009-2013 has been approved which shows by using different materials, namely "Fluorinated cyclic olefin electret film", the frequency response frequency diagram can reach 50 kHz at 100dB. When these new enhanced electrets are combined with traditional dome headphone drivers, headphones can be manufactured that are recognized by the Japanese Audio Society as worthy of joining the Hi Res Audio program. US Patent 8,559,660 B2. 7,732,547 B2.7,879,446 B2.7,498,699 B2.
Orthodynamics
Orthodynamic headphones (also known as Planar Magnetics) use similar technology for electrostatic headphones, with some fundamental differences. They operate the same as Planar Magnetic Speakers.
The orthodinamic driver consists of a relatively large membrane containing an embedded wire pattern. These membranes are hung between two sets of permanent magnets, opposite directions. The current passing through the wire embedded in the membrane produces a magnetic field that reacts with a permanent magnetic field to induce motion in the membrane, which produces sound.
Balanced armature
A balanced armature is a sound transducer design intended to improve the electrical efficiency of an element by removing pressure on the diaphragm characteristics of many other magnetic transducer systems. As schematically shown in the first diagram, it consists of a rotating magnetic armature that moves so that it can move in a permanent magnetic field. When precisely centered in a magnetic field there is no total force on the armature, hence the term 'balanced'. As illustrated in the second diagram, when there is an electric current through the coil, it memagnitasi armatures one direction or another, causing it to rotate one way or another about the pivot so as to move the diaphragm to make sound.
The design is mechanically unstable; a slight imbalance keeps the armature attached to one magnetic pole. A hard enough restoring force is required to hold the armature in the 'balance' position. Although this reduces its efficiency, this design can still produce more noise from less power than others. Popularized in the 1920s as Baldwin Mica Diaphragm radio headphones, balanced armature transducers were perfected during World War II for use in military-powered sound phones. Some of them achieve amazing electro-acoustic conversion efficiency, in the range of 20% to 40%, for narrow bandwidth voice signals.
Today they are usually only used in ear headphones and hearing aids, where their high efficiency and small size are the main advantages. They are generally confined to the extremes of the auditory spectrum (eg below 20 Hz and above 16 kHz) and require a better seal than other racer types to give their full potential. The high-end models can use some armature drivers, dividing the frequency range between them using a passive crossover network. Some combine haunted drivers with small moving coil drivers to increase bass output.
The initial loudspeaker for the radio receiver uses a balanced armature driver for its cone.
Thermoacoustic Technology
The thermoacoustic effect produces sound from the audio frequency of a Joule heating conductor, an effect that is not magnetic and does not vibrate the speaker. In 2013, a thin thread of carbon nanotube threads based on thermoacoustic mechanisms was demonstrated by a research group at Tsinghua University. The self-produced thin CNT earpiece has a working element called thin thread CNT thermoacoustic chip. Such chips are composed of a thin CNT thread layer supported by silicon wafers, and periodic grooves with a certain depth are made on the wafer by micro fabrication methods to suppress heat leakage from the CNT yarn to the substrate.
Other transducer technology
Transducer technology used much less commonly for headphones including Heil Air Motion Transformer (AMT); Piezoelectric film; Planar magnetic tape; Magnetostriction and Plasma-ionization. The first Heil AMT headphone is marketed by ESS Laboratories and is essentially an ESS AMT tweeter from one of the company's speakers driven in full range. Since the turn of the century, only Precide of Switzerland produces AMT headphones. Piezoelectric film headphones were first developed by Pioneer, their two models using flat film sheets that limit the maximum volume of air movement. Currently, TakeT produces piezoelectric film headphones shaped similar to AMT transducers but, like the Precide driver, has variations in the size of the transducer folds above the diaphragm. It also incorporates a two-way design with the inclusion of a special tweeter/supertweeter panel. The folded shape of the diaphragm allows transducers with larger surface areas to fit in smaller spaces. This increases the total volume of air that can be moved on each transducer journey considering the radiating area.
The Magnetostriction headphones, sometimes sold under the Bonephones label, work by vibrating against the sides of the head, transmitting sound through bone conduction. This is helpful in situations where the ear should be blocked, or for a deaf person for reasons that do not affect the neural hearing aid. Nevertheless, the headphone magnetostriction is limited in their loyalty compared to conventional headphones that rely on normal ear work. In addition, in the early 1990s, a French company called Plasmasonics tried to market plasma-ion headphones. No known examples of remaining functionality.
Benefits and limitations
Headphones can prevent others from hearing the sound, either for privacy or to prevent disturbing others, such as listening in the public library. They can also provide greater sound loyalty levels than loudspeakers at the same cost. Part of their ability to do so comes from the lack of need for corrective room maintenance with headphones. High quality headphones can have very low frequency responses up to 20 Hz in 3 dB. While the loudspeaker must use relatively large speaker drivers (often 15 "or 18") to reproduce low frequencies, the headphones can accurately reproduce bass and sub-bass frequencies with the speaker driver only 40-50 millimeters (or smaller, as is the case with headphone in-ear monitor). The impressive low frequency performance of headphones is possible because it is much closer to the ear so they only need to move relatively small air volumes.
Marketed claims such as 'frequency response 4 Hz to 20 kHz' are usually overkill; product responses at frequencies lower than 20 Hz are usually very small. Headphones are also useful for video games that use 3D position processing audio algorithms, as it allows players to better assess the position of an off-screen sound source (such as an opponent's tracks or gunfire).
Although modern headphones have been widely sold and used for listening to stereo recordings since the Walkman release, there is a subjective debate about the nature of their stereo sound reproduction. The stereo record represents the position of the horizontal depth gesture (stereo separation) through the volume and the questionable phase noise difference between the two channels. When the sounds of the two speakers mix, they create the phase difference that the brain uses to find direction. Through most headphones, since the right and left channels do not join this way, the illusion of the phantom center can be considered lost. The sound of loud panning is also heard only in one ear and not from one side.
Binaural records use different microphone techniques to encode direct directions as phases, with very few amplitude differences below 2 kHz, often using a doll's head. They can produce a very real spatial impression through headphones. Commercial records almost always use stereo recording, rather than binaural, because listening to the loudspeaker is more common than listening to headphones.
It is possible to change the spatial effect of stereo sound on headphones, to be closer to presenting the reproduction of speakers, using cross-frequency-dependent feeds between channels.
Headsets can have ergonomic benefits over traditional phone handsets. They allow call center agents to maintain better posture without the need to hold the handset hands or tilt their heads aside to carry them.
Hazards and volume solutions
Using headphones at a sufficiently high volume level may cause temporary or permanent hearing loss or deafness. The volume of headphones often have to contend with background noise, especially in noisy places such as subway stations, airplanes, and large crowds. Extended periods of exposure to high sound pressure levels made by headphones at high volume settings can be detrimental; however, one hearing expert found that "less than 5% of users chose volume levels and listened often enough to risk hearing loss." Some manufacturers of portable music devices have tried to introduce safety circuits that limit output volumes or warn users when hazardous volumes are in use, but the concept has been rejected by the majority of people who buy, preferring high volume personal selections. Koss introduced the "Safelite" cassette line in 1983 with such warning lights. The line was halted two years later due to lack of interest.
The French government has imposed restrictions on all the music players sold in the country: they should not be able to produce more than 100dBA (the threshold of hearing damage when listening is extended is 80dB, and the threshold of pain, or theoretically direct hearing loss, is 130dB). Motorcyclists and other sports-power riders benefit by using legal foam earplugs to do so to avoid excessive street noise, engines, and wind, but their ability to hear music and speak intercom actually increases when they do it. The ear can usually detect 1-billion atmospheres of sound pressure level, making it very sensitive. At a very high level of sound pressure, the muscles in the ears tighten the tympanic membrane and this leads to minor changes in the geometry of ossicles and stirrings that result in a lower power transfer to the inner ear oval window (acoustic reflex).
The risk of hearing loss also depends on exposure time. The higher the volume, the faster the hearing loss occurs. According to the OSHA safety guidelines, workers should be exposed to 90dBA noise for up to 8 hours to avoid hearing loss. Increased to 95dBA only cut safe exposure only 4 hours. But there is little specific consensus about the level of exposure that is safe. NIOSH has a recommended 8 hour exposure limit for 85dBA. In addition, the increase to 93dBA rather than 95dBA divides the safe exposure time to 4 hours.
Some studies have found that people are more likely to increase volume to unsafe levels during heavy exercise. A study in Finland recommends that athletes should adjust their headphone volume to half of their normal loudness and only use it for half an hour.
Noise cancellation of headphones can be considered dangerous due to lack of awareness that the listener may have with his environment. Headphone noise absorbers are so effective that a person may not be able to hear the traffic coming or take notice of the people around them. There is also a general danger that music in headphones can distract the listener and lead to dangerous situations.
The usual way to limit the volume on a device that drives headphones is to limit the output power. This has an undesired additional effect as it relies on the efficiency of headphones; devices that generate the maximum power allowed may not generate enough volume when paired with low-efficiency, high-impedance equipment, while the same amount of power can reach dangerous levels with very efficient earphones.
See also
- Bone conduction
- Digital audio player
- Earpad
- Headphone amplifier
- In-ear monitor
- List of headphone manufacturers
- Headphones noise silencer
References
External links
- Audio Benchmarking Headphone Test Files
Source of the article : Wikipedia
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