Systems that keep rockers and performance artists in tune—and safe

Personal monitoring systems have come a long way in terms of sound quality and comfort since their inception in the late 1980s. In fact, it’s fair to say that personal, or in-the-ear monitoring (IEM) systems, can be found on most major concert tours today, and the acceptance of these systems among performers is growing.

Manufacturers of personal monitoring systems offer extensive educational booklets on selection of an appropriate system and system operation, information that exceeds the space limitations of this overview. This article describes the mechanics and shortcomings of onstage monitoring, compares personal monitors to traditional floor wedge monitors and, most importantly, discusses the role of the audiologist in selecting the appropriate earpiece and guiding the musician to safe use.

Traditional Onstage Monitoring
Musicians need to hear themselves on stage over myriad competing sound sources. The PA system, crowd noise, onstage amplifiers, and escalating volume levels from other band mates trying to hear themselves all add to the difficulty in hearing one’s own instrument or voice during a live performance. The solution has been to place loudspeakers on stage and turn them around to face the performer. These highly directional speakers are typically wedge-shaped and are placed on the stage in front of the musician, pointing at their knees so they don’t block sight lines for the audience. Square-shaped speakers (called side-fills) are often added to both sides of the stage to provide even more sound reinforcement for the performers (Figure 1).

 FIGURE 1. Diagram of stage setup using loudspeaker floor monitors (Mon) and side fill amplifiers for guitarists (G), vocals (V), bass (K), and drums (D). Instrument amplifiers behind musicians not pictured.

With the ever-increasing size of venues and stages, more loudspeakers are needed to provide sound to all areas of the concert venue. Concerts of this magnitude require two sound engineers. The front of house (FOH) engineer mixes the main sound system for the audience, and he usually works from a sonically strategic position near the center and toward the rear of the main floor. The monitor engineer (ME), working out of sight from the side of the stage, creates separate mixes for the performers through the onstage loudspeakers and/or IEM systems, independent of the FOH mix.

These loudspeaker monitor systems present a variety of problems for the performers, the audience, and both of the engineers. The performers are forced to turn up the volume of their monitor loudspeakers to hear over the competing sound sources, while the monitor engineer is challenged to manage the resulting feedback from wedges. As a result, all onstage personnel are exposed to ear-shattering sound levels. In turn, the FOH engineer has no choice but to increase the volume of the house speakers to override the onstage sound that is now interfering with the FOH mix. The audience then suffers through excessive sound levels and compromises to the quality of the FOH mix.

Personal Monitoring
Personal monitoring has revolutionized onstage sound reinforcement. The development of personal monitors was driven by the need to provide an onstage listening experience that surpassed the limitations of traditional floor monitor systems.

Since the objective of onstage monitor systems is to allow the performers to hear themselves, and given the above-mentioned limitations of wedges, presenting the monitor mix through smaller speakers at or in the ear is an attempt to address the shortcomings of having speakers on stage. Bands using in-the-ear monitoring systems can remove all or most floor monitors from the stage, reducing onstage volume levels significantly. This in turn allows the FOH mix to be executed with greater fidelity and at more reasonable levels (Figure 2).

FIGURE 2. Diagram of stage setup using in-the-ear personal monitors. Instrument amplifiers are sometimes removed from stage as well.

 FIGURE 3. IEM system including transmitter, belt pack receiver/amplifier, and custom personal monitors.

A personal in-the-ear monitoring system consists of a belt-pack amplifier that is either hard-wired or wireless, and a set of earphones with tiny loudspeakers (Figure 3). An in-the-ear monitoring system offers the following benefits over traditional stage loudspeakers:

1) Improved sound quality
2) Improved pitch perception
3) Improved timing
4) Reduced feedback
5) Consistent sound quality between venues
6) Reduced vocal fatigue
7) Mobility (with wireless systems)
8) Portability
9) Lower sound levels and increased sound quality for the audience
10) Ability to reduce sound-level exposure for the performers

What Hearing Care Professionals Should Know
As the demand for this technology becomes greater, hearing care professionals are seeing an increasing number of musicians requesting “ear impressions” for custom-molded personal monitors. Since concert sound reinforcement strategies are foreign to most of us, the question is, “What does an audiologist need to know to provide a quality service to this new client base beyond shoving silicone in their ears?”

Before one can provide guidance on selection of earpieces and safe use, one should have a basic understanding of earpiece technology. The key to successful personal monitor use depends on the quality of the earphone. IEM earphones come in three types:

• Walkman®-style ear buds.
• Universal-fit earphones.
• Custom-molded earphones.

The goal is to provide a full-bandwidth stereo mix to the performer on stage while acoustically blocking out the competing sound sources. Good earphone designs allow the performer to hear more detail than is possible with floor monitors, resulting in reduced sound levels at the ear. Ear-bud type earphones are not favored for onstage applications, as they do not offer the degree of isolation required. For this reason, in-the-ear designs dominate the marketplace.

 FIGURE 4. Universal earphone (right) with custom sleeve (left).

Most IEM systems include a universal-fit earphone along with the wireless or hard-wired equipment so the musician can get started immediately (Figure 4). These earphones come with a variety of generic tip couplers, ranging from foam cylinder to silicone mushroom cap or triple flanged shapes, providing the user with options for the best comfort and isolation from ambient sound. These can be upgraded with a custom sleeve mold to provide more comfort and isolation and is preferred for active performers or those with small or sharply bending ear canals. These custom attachments are made of soft materials, much like a power BTE mold.

 FIGURE 5. Sensaphonics 2X-S two-speaker soft silicone custom IEM.

The best fit, comfort, and sound quality come from custom molded earpieces—used by virtually all performers who can afford them (Figure 5). Resembling in-the-ear hearing aids, the custom earphone completely encases micro-speakers that are positioned within each unique mold in a way that is more cosmetic and comfortable than the universal monitors. These custom personal monitors come in a variety of materials including soft (silicone), hard (acrylic), and hard acrylic with soft acrylic canal. Soft materials provide the best isolation and comfort for extended use.

Micro speakers (transducers) are categorized as either dynamic or balanced armature type. Dynamic diaphragms are found in Walkman-type earbuds. These buds are designed for the open ear canal and need air vents on the outside of the casing to allow full movement of the diaphragm. Consequently, custom monitors with dynamic type speakers offer little or no isolation because of the venting needed for maximized sound quality.

Balanced armature speakers are the same type of speaker that is found in hearing aid technology. However, because full bandwidth reproduction is required, special hybrid and, more recently, active speaker technology, are employed to meet performance demands. They come as a wideband single driver or in combinations of two or even three to satisfy the musician’s desire for fuller bass response. Musicians should be warned that, with additional speakers, come more volume. Three-speaker monitor output has been measured at 131 dBA at the eardrum during performance! No one is going to protect his/her hearing at that level.

Balanced armature transducers are more widely available than dynamic diaphragms because they actually sound better the more the ear is isolated from ambient sound, enhancing the signal (monitor mix) to noise (competing sound sources) ratio in the ear canal. The better the SNR, the lower the sound level needed to hear accurately. In short, soft materials provide the greatest amount of isolation, which in turn improves sound quality, thus allowing the user to hear accurately at safer levels.

Ironically (or perhaps inevitably), isolation also creates a new problem for the musician: Performers complain about feeling detached from the audience and fellow band members. They will often remove one earpiece in order to “feel the room again” or to communicate with band mates or the audience between songs. Inventive monitor engineers have maximized monitor mixes using advanced audio tools, often miking the audience to bring in the room sound to replicate hearing on stage as one would without something occluding the ear. Although these techniques have partially remedied the complaints associated with isolating monitors, they do not allow the musician to use the reflective properties of the head and pinna needed for localization. This is typically the main objection to going in-ear.

 FIGURE 6. Sensaphonics 3D Active Ambient IEM system.

A new system has been developed to address this obstacle. Tiny, hybrid mics, designed to take high SPL peaks without overloading, are embedded in the earpieces and equalized to the average response of an open ear canal (Figure 6). The ambient sound is now completely natural while directional cues are retained. The sound from these ambient mics is sent to a body pack, where an active circuit combines the signals with the input from the monitor system, producing a full mix of music and local ambient sound at the ear. As a result, the artist can speak with band members on stage during a performance while retaining the benefits of isolation.

The Safe Use of Personal Monitors
Given the fact that personal monitors are capable of producing damaging sound levels, how does one direct the musician to safe use and, more importantly, how does the musician decide what is a safe level to monitor? Currently, the only method to measure the sound levels from a personal monitor is through probe-mic measurements taken during a sound check or rehearsal. From these readings, musicians can be directed to safe levels using time-weighted averages.

It should be noted that club musicians play an average of 3 hours a night for as many nights per week as possible. Consequently, the safe limits must be lowered in accordance with time of exposure. Shows for artists playing on major tours last about 90 minutes each night for a few months out of the year, so louder exposures are allowed. Unfortunately, most probe-mic equipment is not portable or designed for A-weighted measurements, so the musicians are left with their own perception of what is deemed “too loud.”

A yet-to-be-published study of first-time users of personal monitors suggests that musicians tend to match the levels they were accustomed to while using floor monitors. Given their trained auditory memory for pitch and timing, this finding is not surprising. Why not loudness as well?

A: Left ear of Musician #1: Male guitarist/singer in a club band, who has worked 4 shows/week, 3 hours/night for 8 years

B: Right ear of Musician #1

C: Left Ear of Musician #2: male guitar player in a major touring act, arena venues, touring 6 mths/yr @ 1-2 hour shows for 6 years

D: Right Ear of Musician #2

FIGURE 7. Comparison of two professional musicians’ ears who have actively pursued hearing conservation: A singer/guitarist in a band who has regularly played club gigs during the last 8 years (7a-b), and a guitar player of a major touring band who has toured with the band 6 months per year for 6 years (7c-d).

However, it is possible to maintain one’s hearing by using personal monitors intelligently. Figure 7 portrays the baseline and follow-up audiograms on musicians in different musical environments. Musician 1 (Figures 7a-b) plays in a club environment, doing 3-hour shows 4-5 nights per week, while Musician 2 (Figures 7c-d) is in a major touring band playing large arenas for 3-4 months per year for about 90 minutes per show. Note that both were interested in preserving their hearing, used soft, isolating silicone molds with 2 speakers, and followed the safety recommendations of in-ear sound level measurements performed during sound check. Their repeat audiograms indicate no change in hearing over 6 years of major touring and 8 years of regular club gigging.

This emphasizes the importance of the audiologist’s role in guiding the musician to safe use. The following are some helpful tips to offer the musician:

1. Test and re-test hearing. Although this is not mandatory as in industry, it is still the foundation of any hearing conservation effort, and musicians should be strongly encouraged to participate. Identifying small changes in a short time sure beats finding larger ones after a few years of misuse.

2. Recommend isolating earmolds. The softer the material, the greater degree of isolation.

3. Avoid venting the monitor. Venting not only results in a reduction of bass response with armature-type transducers, but also allows stage volume to bleed into the ear uncontrollably. This forces the listener to turn up the volume of the belt pack to overcome the levels from competing sound sources.

4. Wear both earpieces! Removing one monitor causes the listener to increase the volume in the occluded ear to compensate for the loss of binaural summation. It also exposes the open unprotected ear to loud ambient sound levels. Furthermore, volume entering through the open ear can contribute to central masking, again resulting in the musician turning up the single monitor to perceive the same volume as when both monitors are used. Using stationary ambient (audience) mics or earpieces with integrated hybrid mics are the only safe methods for resolving problems associated with isolation.

5. Use peak limiters or compressors. Most systems include a peak limiter in the amplifier belt pack. Some bands use outboard limiters. Both methods help protect the user from loud bursts of sound and are an important link of the preservation chain. However, they do not prevent the performer from turning the volume to unsafe levels on a daily basis!

6. Know the danger signs. Be aware of warning signs such as tinnitus and temporary threshold shift (TTS) after a performance.

Because musicians have to see an audiologist to get the ear impressions required for custom monitors, we have a great opportunity to offer our valuable expertise in hearing conservation. I tell my clients: “You can use these and lose your hearing, or you can use these to preserve it. Which do you want to do?” Most will want to hear more. You’d be surprised at how often a musician comes in expecting only to get ear impressions for their new custom monitor and leaves appreciating the wealth of information given on how to preserve their hearing. Audiologists are needed not just to take impressions and provide safety information, but also to instill value in preserving hearing and motivating musicians to follow through.

Develop a case history form that identifies risk factors for hearing loss beyond exposure to loud music. Find out the performers’ motivation for using personal monitors. Test their hearing at all frequencies, including the half octaves. Educate them on the astonishing complexities of the hearing mechanism. Do this and you will not only be contributing to prolonging the careers of those artists who give us so much through their music, you will also be establishing yourself as an expert on personal monitoring.

 Michael Santucci, MS, is president of Sensaphonics Hearing Conservation Inc, Chicago, and offers seminars on protecting the hearing of those involved in the performing arts. His clients include major rock bands, NASA, Indy racing drivers, and television broadcasters.

Correspondence can be addressed to HR or Michael Santucci, Sensaphonics Hearing Conservation Inc, 660 N Milwaukee Ave, Chicago, IL 60622; email: [email protected].