The primary goal of HPDs designed for musicians is to reduce sound exposure levels with minimal distortion to the music. Traditional HPDs typically attenuate higher-frequency sounds more than lower-frequency sounds, leading to muffled or distorted hearing.5 One approach to reducing sound levels with minimal distortion is to fit musicians with a uniform attenuation earplug (UAE), a filtered earplug designed to provide linear attenuation across a wide frequency range, typically from 250 to 4,000 Hz. Several types of UAE are available on the market. These best practices in fitting, verification, and patient counseling can help promote effective hearing protection practices among musicians.
For a laboratory to make a properly sized UAE, the clinician must take a deep ear impression that contains the entirety of the patient's concha and reflects as much of the ear canal as possible. At a minimum, the impression should extend to the second bend of the ear canal, preferably several millimeters beyond the second bend. As the ear canal is dynamic with jaw motion, the impression should be taken in the same position that the device will be used. For example, singers should open their jaw and sing while having an ear impression taken. A trumpet player should play or simulate playing his or her instrument while the impression cures. To ensure patient safety, clinicians should be well trained in taking deep ear impressions and managing any medical incident that may occur.
FITTING AND MODIFICATIONS
Clinicians should fit musicians with UAEs in person. Research shows that workers who wear custom hearing protection typically achieve poorer attenuation in their daily use than would be expected based on the HPD label.6 If the UAE is not comfortable, physical modifications can be done by the clinician, or the product can be returned to the laboratory. Modifications should be completed judiciously because reducing the length of the UAE can change its acoustic properties and reduce the uniformity of the attenuation.
Earplugs for musicians must provide high-fidelity sounds. Clinicians should verify that a high-fidelity HPD is made according to an individual's specifications and functions. Variance in ear canal shape and size affects the effectiveness of an HPD, so the performance of an earplug can vary widely depending on the individual fit. To ensure the best possible fit of an HPD, the clinician should verify the attenuation achieved by assessing the flatness or uniformity of the attenuation response across frequencies.
Several methods have been proposed to measure UAE attenuation, including probe microphone and real-ear attenuation at threshold (REAT) measures. Probe microphone measures are commonly recommended for measurement of earplug attenuation in the clinic and achieved by subtracting the sound level in situ with the HPD in the ear from the sound level of the open ear.3,7 REAT measures are the gold standard for calculating HPD attenuation, and require measuring hearing thresholds in a sound-attenuated booth with the HPD on and off to determine attenuation.
Portnuff and Price8 evaluated 30 UAE fittings by comparing attenuation measurements using the REAT and probe microphone methods with a modified probe microphone reference system designed for laboratory measurements. This study identified some key findings for the verification methods. First, the probe microphone measurements can provide efficient results. However, the probe tube may cause a leak in the earplug seal. It can be difficult for the clinician to assess whether this leak is due to the probe tube or a poorly sealed earplug. Second, Portnuff and Price identified REAT testing as a valid method for verification, with best results seen when using soundfield measurements (with contralateral ear masked) and second-best results seen when testing with circumaural earphones. Further research by Portnuff9 found that the best frequencies to test are 250, 1,000, 2,000, and 4,000 Hz. Low-frequency attenuation values can identify slit leaks in the earplug, and higher-frequency attenuation values can show the uniformity of the attenuation across frequencies.
At the University of Colorado Hospital, the protocol is to verify every UAE fitted in the hospital's Hearing and Balance Clinic. However, UAEs are commonly purchased at large events or festivals where impressions are taken and the earplug is mailed to the musician. Though this is convenient for the earplug user, this type of service delivery does not meet best practice standards.
REMEDYING POOR ATTENUATION
UAEs found to have inadequate uniform attenuation after verification need to be remade. Unfortunately, no research is available to date on the appropriate minimum level of attenuation uniformity or acceptable level of deviation from a truly flat attenuation. Therefore, clinicians should use their best judgment to determine the acceptable range of attenuation for their patients. If a UAE does not conform with the manufacturer's specifications or the patient's desires, the clinician should consider having the device remade or suggesting a different HPD.
EDUCATION AND COUNSELING
The use of an earplug will change the way that a musician hears an instrument. Most musicians who learn to play at a young age usually have a strong auditory memory and use their hearing to help fine-tune the timbre of their instrument. As such, they will need to re-learn how to play the instrument while using a UAE.10
A musician must play in his or her own environment to “ear train” with the new earplugs. Additional best practices include practicing with a UAE while using visual cues for loudness (e.g., a sound level meter), recording the practice session, then listening to the recording critically. Musicians have a tendency to play at higher intensity levels when using HPDs, so they must learn how to play at appropriate sound levels to avoid overplaying and reduce the risk of performance injury.
Musicians who are exposed to high levels of sound should be enrolled in a formal or informal hearing conservation program (HCP; Table 1). Clinicians should educate musicians about sound exposure and hearing loss prevention. This can motivate musicians to use HPDs and help them learn how to modify their sound exposure. Musician should understand that their overall sound exposure, including all occupational and recreational exposure, increases their risk for hearing loss when exceeding permissible exposure levels. Without proper education and motivation, musicians are unlikely to effectively reduce their exposure, whether through using HPDs or reducing sound levels.11 Musicians with significant sound exposure should also be enrolled in an audiometric monitoring program and monitor their hearing system function on an annual basis. Those who see shifts in their hearing thresholds may be motivated to take more significant action to prevent MIHL.
HPDs can be a valuable part of musicians' overall hearing conservation, but clinicians must make sure that custom devices are properly fitted, verified, and supported with proper education and counseling. Failure to do so may result in incorrect use of the device, which defeats the goal of using HPDs. For musicians, their sense of hearing is a critical instrument, and clinicians play a key role in educating these patients on how to best maintain and preserve this instrument for a lifetime.
Thoughts on something you read here? Write to us at HJ@wolterskluwer.com
1. Royster JD, Royster LH, Killion MC Sound exposures and hearing thresholds of symphony orchestra musicians J Acoust Soc Am 1991 89 6 2793–2803
2. Zhao F, Manchaiah VKC, French D, Price SM Music exposure and hearing disorders: An overview Int J Audiol 2010 49 54–64
3. Chasin M Musicians and the Prevention of Hearing Loss. San Diego, CA: Singular; 1996.
4. Phillips SL, Henrich VC, Mace ST Prevalence of noise-induced hearing loss in student musicians Int J Audiol 2010 49 309–316
5. Niquette P Hearing Protection for Musicians. Hear Rev. 2006:52, 55, 56, 58.
6. Berger EH, Franks JR, Lindgren F, et al International review of field studies of hearing protector attenuation. Scientific Basis of Noise-Induced Hearing Loss. New York, NY: Thieme Medical Publishers; 1996:361-377.
7. Trompette N, Kusy A, Ducourneau J Suitability of commercial systems for earplug individual fit testing. Appl Acoust. 2015;90:88-94. doi:10.1016/j.apacoust.2014.11.010.
8. Portnuff CDF, Price D Validation of clinical techniques for verification of uniform attenuation earplugs. Int J Audiol
. 2019;58(sup1):S33-S39. doi:10.1080/14992027.2018.1532119.
9. Portnuff CDF Hammershøi D, Boley J Best Practices for Fitting, Dispensing, and Verifying Hearing Protection Devices for Musicians. In: eds. 2018 AES International Conference on Music-Induced Hearing Disorders. Chicago, IL: Audio Engineering Society; 2018. doi:10.17743/aesconf.2018.978-1-942220-20-6.
Copyright © 2019 Wolters Kluwer Health, Inc. All rights reserved.
11. O'Brien I, Driscoll T, Ackermann B Hearing Conservation and Noise Management Practices in Professional Orchestras. J Occup Environ Hyg
. 2012;9(10):602-608. doi:10.1080/15459624.2012.715519.