In-ear monitor

Lore & Background

The origins of in-ear monitors as a tool in live music performance trace back to the mid-1980s. They were developed as an alternative to traditional stage monitor systems, which used floor wedges—loudspeakers placed on stage directed toward performers. Floor wedges increased onstage volume to potentially damaging levels and allowed sound to spill, muddying the stage mix. In contrast, IEMs allow each performer to have their own monitor mix, and since they wear an IEM in each ear, they can hear a stereo mix if the system permits, with different elements panned to each ear. More recent advances allow the user to adjust the amount of ambient noise filtered by the IEM.

Most professional stage in-ear monitor systems use wireless technology, consisting of a stationary offstage transmitter and an onstage receiver worn by the performer. Transmitters output either one stereo mix or two mono mixes, and any number of receivers can receive a single mix. The transmitters and receivers transfer audio wirelessly via VHF or UHF radio frequencies; UHF systems generally sound better and are less susceptible to frequency interference. The IEM cable plugs into a 3.5 mm stereo jack on the receiver pack, typically clipped onto the performer's belt, guitar strap, clothing, or placed in a pocket.

Custom-molded IEMs are made from impressions taken by an audiologist, using a high-viscosity impression material with a deep impression of the ear canal. The musician mimics their embouchure while the impression material sets for a comfortable fit during performance. Custom IEMs come in a variety of colors but are usually clear or skin-colored; some manufacturers can place custom artwork on them. Passive ambient IEMs have a small hole drilled into the earpiece to allow natural ambient sound in, while active ambient IEMs use external microphones to reproduce ambient sound that mimics the frequency response of the open ear.

Reader's Guide

In-ear monitors have significantly changed live sound reinforcement and personal audio monitoring. By replacing floor wedges, they reduce onstage volume, lowering the risk of hearing damage from loud instruments such as drum kits or large guitar stacks. They also improve the clarity of the mix for performers by eliminating sound spill. However, one trade-off is the loss of crowd noise and audience comments, such as calls for an encore. To address this, microphones are often placed near each side of the stage facing the audience to capture crowd noise back into the performers' mixes; larger shows may use several such microphones across the front of the stage.

The effectiveness of an IEM depends heavily on the seal created in the ear canal. Universal IEMs include various foam and silicone tips to achieve a comfortable seal, while custom-molded IEMs provide better comfort and isolation, offering between 25 and 34 decibels of noise reduction. Custom IEMs made of softer silicone can be inserted deeper for more isolation. Driver technology varies: balanced armature drivers, originally invented for hearing aids, are used extensively, with top models carrying up to 18 drivers for faster response and higher dynamic range. Dynamic drivers are cited for better bass response, planar magnetic drivers offer high clarity with low distortion, and electrostatic and electret drivers are rarer or used in hybrids. Hybrid IEMs combine driver types to optimize frequency ranges. Television studios use earpieces with a specialized intercom called an interruptible foldback (IFB) for communication.

Did You Know?

• Custom-molded IEMs can provide between 25 and 34 decibels of noise reduction.
• Some top IEM models carry as many as 18 balanced armature drivers.
• UHF wireless systems generally sound better than VHF systems and are less susceptible to frequency interference.
• Television studios use earpieces with an interruptible foldback (IFB) intercom system.