
An in-ear monitor (IEMs), in-ear, or colloquially earpiece is a listening device placed into the ear. More narrowly, the term in-ear monitor is defined as such a device used by
musician
A musician is someone who Composer, composes, Conducting, conducts, or Performing arts#Performers, performs music. According to the United States Employment Service, "musician" is a general Terminology, term used to designate a person who fol ...
s,
audio engineer
An audio engineer (also known as a sound engineer or recording engineer) helps to produce a recording or a live performance, balancing and adjusting sound sources using equalization, dynamics processing and audio effects, mixing, reproduc ...
s and
audiophile
An audiophile (from + ) is a person who is enthusiastic about high-fidelity sound reproduction. The audiophile seeks to achieve high sound quality in the audio reproduction of recorded music, typically in a quiet listening space in a room with ...
s to listen to music or to hear a personal mix of vocals and stage instrumentation for
live performance or
recording studio
A recording studio is a specialized facility for Sound recording and reproduction, recording and Audio mixing, mixing of instrumental or vocal musical performances, spoken words, and other sounds. They range in size from a small in-home proje ...
mixing, often specifically in order to hear themselves through a sound system in real time. They are also used by
television presenters
A television presenter (or television host, some become a "television personality") is a person who introduces or hosts television show, television programs, often serving as a mediator for the program and the audience. It is common for people ...
to receive vocal instructions, information and breaking news announcements from a producer that only the presenter hears. They are often custom-fitted to an individual's ears to provide comfort and a high level of
noise reduction
Noise reduction is the process of removing noise from a signal. Noise reduction techniques exist for audio and images. Noise reduction algorithms may distort the signal to some degree. Noise rejection is the ability of a circuit to isolate an u ...
from ambient surroundings. Their origins as a tool in live music performance can be traced back to the mid-1980s.
A
stage monitor system is any system that provides a mix of audio sources to a performer on stage. Traditionally, loudspeakers were placed on the stage directed toward the performers. These loudspeakers can have disadvantages. First, floor wedges greatly increase the onstage volume, in some cases to levels which could potentially damage hearing. Second, while floor wedges can be placed in front of a particular singer, guitarist, bassist, or drummer, the other musicians can often hear the other musicians' wedge mixes. In a sophisticated monitoring system, every band member can have their own monitor mix, which is their particular preference of vocals or instruments.
Since performers wear an IEM in each ear, they can also hear a stereo mix if a particular monitor system allows it. This can allow the additional definition of the audio by
panning different elements (vocals, drums, etc.) to each ear. More recent advances allow the user to adjust the amount of ambient noise filtered by the IEM.
One additional consideration for mixing IEMs is that while eliminating floor wedges can improve the overall clarity of the mix for the performers and decrease the overall volume onstage, one important piece that is often lost is crowd noise and crowd comments, such as the audience calling for an encore. It is not uncommon for a microphone to be placed near each side of the stage, facing the audience, to provide a method to capture some of the crowd noise and audience comments back into the performers' IEM mixes. Larger live shows can have several microphones for this purpose spread across the front of the stage, which can also be sent to a
multitrack recording
Multitrack recording (MTR), also known as multitracking, is a method of sound recording developed in 1955 that allows for the separate recording of multiple sound sources or of sound sources recorded at different times to create a cohesive who ...
device used in an
outside broadcast
Outside or Outsides may refer to:
* Wilderness
Books and magazines
* ''Outside'', a book by Marguerite Duras
* Outside (magazine), ''Outside'' (magazine), an outdoors magazine
Film, theatre and TV
* Outside TV (formerly RSN Television), a televi ...
production truck, or other destinations.
Transmitter and receiver
Most professional stage in-ear monitor systems use wireless technology to send the mix to the IEMs. This type of system consists of a stationary offstage transmitter and an onstage receiver (about the size of a deck of cards) that is worn by the performer. There is generally a transmitter for each monitor mix and there is always a receiver for each IEM. The transmitters usually output either one
stereo
Stereophonic sound, commonly shortened to stereo, is a method of sound reproduction that recreates a multi-directional, 3-dimensional audible perspective. This is usually achieved by using two independent audio channels through a configurat ...
mix or two
mono mixes. When the transmitters are set up for two mono mixes, one transmitter can be used for two different mixes. Any number of receivers can receive a single mix.
The transmitters and receivers transfer audio wirelessly via a
VHF or
UHF radiofrequency. Generally speaking, UHF systems sound much better than VHF systems and are more expensive.
UHF systems usually are less susceptible to frequency interference which adds to their level of quality.
Earpieces

The in-ear monitors themselves are the last stage of the signal path in the system. They are placed in the external ear canal and seal against its sides; the effectiveness of this seal is a major part of the effectiveness of the IEM.
Universal IEMs typically include a variety of foam and silicone tips in each pack, with the goal that one pair may create a comfortable seal for the user's ears. If a universal IEM earpiece does not fit a specific person, they may need to order custom in-ear monitors. If there is not a good seal, ambient noise leakage is increased.
Custom molded IEMs are more comfortable to wear and better isolate ambient noise. Depending on the quality of the fit and length of the canal portion of the earpiece, a custom fit in-ear monitor will generally provide somewhere between 25 and 34
decibels
The decibel (symbol: dB) is a relative unit of measurement equal to one tenth of a bel (B). It expresses the ratio of two values of a power or root-power quantity on a logarithmic scale. Two signals whose levels differ by one decibel have a ...
of noise reduction. This means that loud onstage instruments, such as
drum kit
A drum kit or drum set (also known as a trap set, or simply drums in popular music and jazz contexts) is a collection of drums, cymbals, and sometimes other Percussion instrument, auxiliary percussion instruments set up to be played by one p ...
or large 8x12" guitar stacks, are less likely to cause hearing damage for onstage musicians wearing IEMs.
Custom in-ear monitors come in a variety of colors but are usually clear or a color that closely matches the skin color of the performer. Some manufacturers can also place custom artwork directly on the custom in-ear monitors. The IEM cable plugs into a 3.5 mm stereo jack on the receiver pack; typically clipped onto the belt, guitar strap, clothing of the performer, or placed in a pocket. Impressions for custom in-ear monitors are typically taken by an audiologist. To achieve maximum isolation, the audiologist should use a high-viscosity impression material with a deep impression of the ear canal. The musician should also mimic their embouchure while the impression material is setting so that the fit is comfortable while performing. Custom in-ear monitors made of a softer silicone material can be inserted deeper in the ear canal and will provide more isolation from outside noise.
Some performers desire a more natural sound from their IEMs with both the music mix and ambient sounds. Passive ambient IEMs have a small hole drilled into the earpiece to allow some natural ambient sound into the ear canal. This can potentially lead to increased sound exposure as it reduces the signal-to-noise ratio for the mix and causes the musician to increase the levels from the IEM. Active ambient IEMs use external microphones to reproduce the ambient sound in the mix that mimics the frequency response of the open ear and may sound more natural to the performer.
Television studio
A television studio, also called a television production studio, is an installation room in which video productions take place, either for the production of live television and its recording onto video tape or other media such as SSDs, or for ...
s use earpieces with a specialized type of
intercom
An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which funct ...
called an
interruptible foldback (IFB), as a means of communication.
Driver technology
Balanced armature
Originally invented for hearing aids, balanced armature drivers are nowadays used extensively in modern in-ear monitors.
In-ear monitors can function with as little as one armature driver but some of the top models of in-ear monitors can carry as many as 18 balanced armature drivers for faster response, higher dynamic range, and more detailed sound. Notable examples include the
Ultimate Ears Pro UE LIVE (6 balanced armature drivers and 2 dynamic drivers), JH Audio's Layla (12 balanced armature drivers), Noble Audio's K10U (10 balanced armature drivers), and 64 Audio's A18t (18 balanced armature drivers).
Dynamic
The dynamic driver contains a diaphragm with a voice coil attached to it. When an electric current passes through, the voice coil vibrates between the two permanent magnets resulting in the diaphragm moving and producing sound. Adherents of the dynamic driver cite better bass response.
Planar Magnetic
Planar magnetic drivers consists of a thin membrane-like diaphragm lined with a conductive material sandwiched between two permanent magnets. Similar to dynamic drivers, electric current is passed through the magnets causing the diaphragm to produce sound. The large diaphragm allows for high clarity and detail across a wide frequency range with low distortion. Despite early IEMs exhibiting common weaknesses of planer magnetic drivers such as its size and high price, innovations in planar magnetic drivers now allow for newer IEMs that are both smaller and more affordable.
Electrostatic
Electrostatic drivers consists of a thin diaphragm between two metal plates (
stators) and contains no moving parts. Sound is emitted as the alternating flow of static electricity vibrates the suspended diaphragm. Electrostatic in-ear monitors are rare as they are more expensive to manufacture and require a signal amplifier to function. Examples include the STAX SR-003MK2, Shure KSE1200 and KSE1500.
Electret
Functioning identically to electrostatic drivers, electret drivers are permanently charged eliminating the need for an external amplifier. Electret drivers are commonly used as
tweeters paired with other driver types as hybrid IEMs.
Hybrid
Hybrid in-ear monitors utilizes a combination of different driver types. Common hybrids are made up of at least one balanced armature and dynamic drivers. This setup enables each driver to operate at their optimal
audio frequency
An audio frequency or audible frequency (AF) is a periodic vibration whose frequency is audible to the average human. The SI unit of frequency is the hertz (Hz). It is the property of sound that most determines pitch.
The generally accepted ...
range (dynamic drivers for bass response and balanced armature drivers for middle and high frequencies).
Wire
IEMs typically feature a wire-over-ear or wire (straight) down design.
Wire down is easier to put in with one hand, making it more popular for casual use, where it maybe inserted and removed multiple times per day. It can also be more comfortable, as wearing wire-over-ear with glasses may cause extra pressure and chafing behind the ears.
Wire-over-ear is preferred for professional use, providing a more discreet (run wire behind back, in shirt), secure fit (wire hooks onto ears) with reduced
microphonics.
Some wires may come with
MMCX connectors to allow replacement once worn out, add-ons like in-line microphone or bluetooth connectivity or upgrading to cables of higher quality or different appearance.
Safety
Many performers choose to use IEMs as a way to reduce their overall exposure to loud sound and prevent hearing loss. However, education on the use of IEMs is a crucial factor for limiting exposure as performers have a tendency to set their IEMs to similar intensity levels that were previously used in their floor monitors. Musicians need to train themselves to listen at lower levels to take full advantage of the sound level reduction capability of IEMs.
Some musicians with two IEMs may choose to take out one of them during a performance to hear more ambient sound. The increased risk of hearing damage in this scenario are twofold. Removing one IEM negates the improvement in
signal-to-noise ratio
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in deci ...
from isolation and the binaural summation effect which causes an increase in perceived loudness from using two sound sources. Therefore, the performer will likely turn up the IEM in the other ear to improve the signal-to-noise ratio. Also, the ear without an IEM is potentially exposed to loud ambient sound.
Many IEMS use peak limiters or compressors to limit potential damage from sudden loud sounds. However, this does not prevent the performer from turning up the IEM to unsafe levels.
See also
*
*
MMCX connector
*
Studio monitor
Studio monitors are loudspeakers in speaker enclosures specifically designed for professional audio production applications, such as recording studios, filmmaking, television studios, radio studios and project or home studios, where accurate ...
References
External links
*
*
{{Singing
Headphones