Earplug Use


The proper use of hearing protection is not well defined for someone with hyperacusis. If you do not use hearing protection, you run the risk of setbacks or social isolation. If you use hearing protection too often, you run the risk of lowering tolerances further or hindering recovery. Anxiety that often accompanies protection behavior may enhance hyperacusis symptoms as it heightens loudness and pain sensations to a degree. Earplug use is a complex, individual decision that needs to be made with careful consideration of the risks of overprotection. In general, it is more natural for someone with hyperacusis to wear earplugs more often than is necessary which is why emphasis is usually placed on reducing protection.

Overprotection

The overuse of hearing protection is almost universally discouraged based on evidence that it will lower loudness thresholds over time. Risks of overprotection include increased auditory gain, anxiety induced hypersensitivity, and reinforcement of negative associations with sound. Positive results from studies of Sound Therapy & Counseling reinforce the notion that overprotection can prevent people from building sound tolerance. These treatments emphasize a gradual increase in sound exposure rather than sound isolation. It is often recommended that those with hyperacusis walk the fine line between setbacks and overprotection rather than follow a course of isolation and hypervigilance. Practically applying this guideline is not always straightforward.

Click to Show: Evidence, Severe Hyperacusis, Case Study

Earplugs and Increased Auditory Gain
Challenges with Severe Hyperacusis
Overprotection Case Study

Earplugs and Increased Auditory Gain

The study most often cited to support the negative impact of long-term earplug use is the 2003 study led by Craig Formby. This study comprised two groups of individuals with normal hearing. One group wore earplugs for two weeks and the other wore noise generators for 2 weeks. The sound tolerance of those who wore earplugs was reduced on average by 7 dB. The sound tolerance of those who wore noise generators was increased on average by 7 dB. Recovery to original thresholds (a change of 7 dB on average) occurred within 1 week, suggesting that earplugs have a measurable impact on auditory gain. It should be noted that when this experiment was repeated in 2007, there was negligible change in auditory gain after 2 weeks for those who wore earplugs however after 4 weeks there was on average a 6 dB reduction in loudness tolerance. The sample sizes of both studies were unusually small (10 and 8, respectively).

Assumptions in Application to Hyperacusis

  1. The assumption that sound tolerance will reduce more than 7dB is not strongly supported by these studies. In each study, the average sound tolerance changed by a maximum of 7dB whether it was over 1 week, 2 weeks, or 4 weeks. A similar study (Munro 2014) showed thresholds could be mostly restored within 24 hours of earplug removal suggesting this sort of study is not measuring long term plasticity changes relevant to overprotection concerns or sound therapy treatment. For more robust findings, the study should be repeated with a larger sample size and followed over a longer period of time.
  2. There is an assumption that the loudness discomfort thresholds of those with normal hearing and those with hyperacusis are determined by a similar mechanism. At the very least, there is an assumption that the discomfort (loudness or pain) is triggered in hyperacusis patients after the enhanced gain. In 2009, Munro and Blount performed a study similar to Formby that showed this gain similarly shifts acoustic reflex thresholds, suggesting that some gain adjustment occurs early in the auditory system. Potential hyperacusis neurological mechanisms and middle ear mechanisms related to acoustic reflex could be impacted by this gain change. A cochlear mechanism might not be impacted by this gain change. A repeat of the study using individuals with hyperacusis split into subtypes (pain and loudness) would address this more directly.

Challenges with Severe Hyperacusis

While a person with LDLs in the 80s may have little trouble with most household activities without earplugs, a person with LDLs in the 50s can experience pain by simply turning on a water tap. A more problematic issue arises when unexpected environmental sounds cause setbacks, motivating the severe hyperacusis patient to wear protection when sound levels would on average be pain free. For those with severe hyperacusis, even mild sounds can cause physical pain which can make outsiders view their protection behavior as “overprotection.” However, a common theme in most sound therapies is to not push through pain. Thus for severe hyperacusis patients, guidelines can be inconsistent. Whatever the hearing protection used, it is generally recommended that a conscious effort be made to gradually increase sound exposure, ideally with the help of counseling.

A few studies have attempted to address this dilemma of under- vs over-protection by using electronic devices with loudness compression. A study led by Carol Sammeth of Indiana University School of Medicine used such devices with 14 severe hyperacusis patients with mixed success. Most of the severe hyperacusis patients opted to use the devices only in certain circumstances. Myriam Westcott described the usage of a similar device in 4 of her patients (Westcott 2006). The 3 patients who were able to use the device had hearing loss. The 4th patient without hearing loss “found the proximity of even soft sounds intolerable because they were perceived as right next to the ears.” A 2000 study by the Washington University School of Medicine tried a similar method with a 52 year old severe hyperacusis subject. After one year, he still used the devices “all of the time.” Practical issues such as hiss from electronic noise, sound while speaking or eating, and uncomfortable amplification of softer sounds would need to be managed. Although these modified hearing aids with compression and sound isolation may work for some, higher quality sound reproduction and additional customization may be necessary in reducing irritation for others. Sound-compressing earmuffs and earplugs are already commercially available for gun use however compression will not start until 85 dB.

Case Study: Overprotection

Since hyperacusis can improve slowly, it is important to adjust protection behavior as pain thresholds increase. The full case study of a hyperacusis patient written by Norma Mraz and Robert Folmer can be found on Audiology Online. The individual in the study played guitar and developed hyperacusis at age 33. Over the next 10 years his conditioned worsened. He went on long term disability and isolated himself in a rural home. To protect from sound, he did not shower, covered the windows with bricks, muted his television, moved the refrigerator outside, and used earmuffs while typing, cooking, and for other common activities. His LDLs were measured to be 55 dB.

He went through a gradual course of TRT. Over the next 27 months, his living conditions improved. He was able rinse a cloth to wash, removed bricks from the windows, started to play the guitar again, and enrolled at a local university. His post-treatment LDLs, however, were not documented. LDL measurements taken before his treatment caused distress so it is possible he chose to not have them taken at the end of treatment. If this was part of a LDL based study (e.g. a TRT study), he may be dropped from the equation for success rates.

Underprotection

Increased sound exposure can lead to setbacks. A setback is a sudden drop in sound tolerance as opposed to the gradual reduction in sound tolerance that occurs during overprotection. Setbacks are expected during recovery however they are an under-researched aspect of hyperacusis. Setbacks lasting several days are common. Setbacks lasting weeks, months, or years occur less often but can be deeply discouraging. Anecdotally, it seems setback duration and setback severity reduce to a degree in time. Setback duration and severity also seem to be correlated with hyperacusis severity. While there are over 2200 posts on hyperacusis setbacks in the patient forum on chat-hyperacusis.net, no academic papers could be found using a pubmed search. Some clinicians will inform the patient that sound levels below 85 dB (equivalent to noise from heavy traffic) are safe as they are unlikely to cause long-term hearing loss. While this is comforting and good to know, the relevance to setbacks is unclear as long-term hearing loss (often outer hair cell loss) is not suspected to be related to hyperacusis setbacks. Sound levels that trigger setbacks may be dependent on baseline LDLs and the particular subtype of hyperacusis (pain or loudness). There is a glaring need for research into setbacks to assess the consequences of underprotection. Setback thresholds, duration, severity, and frequency should be studied in relation to long-term recovery. Only then should maximum “safe” sound levels be defined.

Click to Show: Evidence

In the 1999 hyperacusis study led by Mart Anari, 67% of patients reported that their tolerance had worsened after exposure to loud sounds; the duration of the setback was usually between 1-3 days. The 2013 CBT clinical trial led by Linda Juris found that 76% patients reported increased sensitivity after sound exposure. A 2007 TRT study by Formby et al looked at the treatment results of 68 patients after therapy. Although a large percentage of the patients had a positive impact from TRT, 7% of the patients who were willing to go to follow up testing showed a loss in tolerance. This loss was not small, at 10dB on average. This highly suggests setbacks.

In the book Tinnitus Retraining Therapy by Jastreboff and Hazell, the authors note that there can be long term consequences when exposing severe hyperacusis patients to sound near their maximum tolerance levels for long periods:

“When [severe] patients are exposed to continuous high levels during pink-noise therapy, cumulative effects occur and tinnitus and hyperacusis are set permanently to a much higher level than before treatment began”
 
-Tinnitus Retraining Therapy by Jastreboff and Hazell

This is an example of long term setbacks resulting from sound levels likely safe for normal ears. The authors state that sound therapy should instead be set to a low volume and increased very gradually depending on the tolerances of the patient. This example is not meant to discourage gradual sound reintroduction. Gradual sound reintroduction is encouraged as results from recent studies suggest it is an effective tool for recovery. Instead, this example is meant to provide evidence for the intuitive assumption that hearing protection and sound environment need to be adjusted according to hyperacusis severity rather than an absolute 85dB value with no proven relevance to hyperacusis. It is clear that further study into setbacks is needed.

Asymmetrical Protection

There are cases of hyperacusis that affect one ear more than the other. This quickly leads to the question, “What happens if I only protect my bad ear?” There is limited research on this topic. Studies suggest that auditory gain in the protected ear will increase. If the asymmetrical symptoms are related to a contraction of the acoustic reflex, sound into the unprotected ear can trigger the reflex in the protected ear as well, which would limit the effectiveness of protection. There are similar concerns about asymmetrical protection as there are for general overprotection.

Click to Show: Evidence

Kevin Munro and Jennifer Blount from the University of Manchester performed a study of asymmetrical (monaural) earplug usage over a one week span. They found that the ipsilateral acoustic reflex threshold (reflex caused by sound on same side) of the protected ear decreased on average by 5 dB while the ipsilateral acoustic reflex threshold of the unprotected ear increased by 3 dB. There appears to be a balancing effect of the gains, leading to higher sensitivity in the protected ear and lower sensitivity in the unprotected ear. Another study led by Munro involved the asymmetrical usage of hearing aids. In this study, LDLs between the right and left ears deviated by an average of 5 dB after one week with the amplified ear able to tolerate more sound than the unamplfied ear. A longer study would show whether LDLs of the protected ear change at a more rapid rate with monaural earplug usage compared to the binaural earplug Formby experiments.

Next: Pain Thresholds


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References

Anari M, Axelsson Alf, Eliasson A, Magnusson L. Hypersensitivity to Sound: Questionnaire data, audiometry and classification. Scand Audiol 1999:28:219-230.

Formby C, Sherlock L, Gold S. Adaptive plasticity of loudness induced by chronic attenuation and enhancement of the acoustic background. J. Acoust. Soc. Am. 2003:114:55-58.

Formby C, Sherlock L, Gold S, Hawley M. Adaptive Recalibration of Chronic Auditory Gain. Seminars in Hearing 2007:28(4):295-302.

Formby C, Gold S, Keaser M, Block K, Hawley M. Secondary Benefits from Tinnitus Retraining Therapy: Clinically Significant Increases in Loudness Discomfort Level and Expansion of the Auditory Dynamic Range. Seminars in Hearing 2007:28(4):227-260.

Jastreboff P, Hazell J. Tinnitus Retraining Therapy. Cambridge University Press. 2007.

Mraz N, Folmer R. Overprotection-Hyperacusis-Phonophobia & Tinnitus Retraining Therapy: A Case Study Audiology Online 2003:http://www.audiologyonline.com/articles/overprotection-hyperacusis-phonophobia-tinnitus-retraining-1105.

Munro K, Walker A, Purdy S. Evidence for adaptive plasticity in elderly monaural hearing aid users. NeuroReport 2007:18(12):1237-1240.

Munro K, Blount J. Adaptive plasticity in brainstem of adult listeners following earplug-induced deprivation. J. Acoust. Soc. Am. 2009:126(2):568-571.

Munro K, Turtle C. Plasticity and modified loudness following short-term unilateral deprivation: Evidence of multiple gain mechanisms within the auditory system. J. Acoust. Soc. Am. 2014:135(1):315-322.

Sammeth C, Preves D, Brandy W. Hyperacusis: Case studies and evaluation of electronic loudness suppression devices as a treatment approach. Scand Audiol 2000:29:28-36.

Pienkowski M, Tyler R, et. al. A Review of Hyperacusis and Future Directions: Part II. Measurement, Mechanisms, and Treatment. American Journal of Audiology 2014:23:420-436.

Valente M, Goebel J, Duddy D, Sinks B, Peterin J. Evolution and treatment of severe hyperacusis. J Am Acad Audiol 2000:11:295-299.

Wang Y, Ren C. Effects of Repeated “Benign” Noise Exposures in Young CBA Mice: Shedding Light on Age-related Hearing Loss. Journal of the Association for Research in Otolaryngology 2012:13:505-515.

Westcott M. Acoustic shock injury (ASI). Acta Oto-Laryngologica 2006:126:54-58.