The world we navigate is full of sound. As this brief note is being written, the sound of lawn mowers, distant traffic, and snatches of conversations accompanied by rhythmic footfalls stream through windows and doors. When we attend to sounds in the environment, it is impossible not to analyze, and evaluate, and then react. We learn to distinguish information-bearing signals from those whose spectra, we’ve learned as listeners, merit minimal attention and low priority. Some sounds are intentionally attention-grabbing—sirens, doorbells, car horns, shouting—and intended to provoke responses from hearers in the vicinity. Indeed, many alerting sounds are constructed deliberately to be as compelling, and in a sense, as annoying as possible, cutting through distractions and other sounds to demand immediate and sustained attention (Patterson, 1990; Vastfjall et al., 2012). Unfortunately, such sounds may be particularly effective, perhaps overwhelming, for a segment of the population that suffers from experiences of excessive loudness, distraction, pain, and discomfort in their presence. The book Hyperacusis and Disorders of Sound Intolerance offers historical accounts, case studies, and new findings reported by individuals whose work in research labs and clinics focuses upon this underserved population.
At present, audiologists and their patients are adept at estimating thresholds of sensitivity, for example, pure-tone air and bone conduction thresholds. However, it is more challenging in the clinic to obtain important measures of suprathreshold processing, particularly those associated with atypical loudness and sound intolerances. As a result, individuals for whom the world of sound is unusually intense, vivid, perhaps perceived as toxic, endure problems that are difficult to assess and quantify. Interventions lack a substantive evidence base to support specific management approaches. Although most audiologists and otologists know of patients for whom everyday sound evokes discomfort, distress, aversion and in some, pain, such symptoms are difficult to quantify, and management correspondingly difficult to enact. Hyperacusis and Disorders of Sound Intolerance is intended to serve our professions’ abiding and growing need to understand sound intolerance mechanisms and their measurement. If, as is likely, the prevalence of tolerance-related complaints increases and diversifies over time, then the associated challenges will require more effort, empathy, and acceptance on the part of all stakeholders.
The book acknowledges the challenges that will be encountered. Indeed, even the vocabulary used to describe such experiences is varied and imprecise, including decreased, reduced, or collapsed sound tolerance, and several different uses of the term hyperacusis. Sometimes these terms end up signifying more or less the same thing, other times, any one of the terms can be ascribed several distinct meanings. Ultimately, the usage of each of these terms varies; given such fundamental differences, as authors and co-editors Marc Fagelson and David Baguley point out, it is not surprising that data regarding the epidemiology and natural history of hyperacusis are sparse, and inconsistent where it does exist.
From the perspective of recent and emerging investigations, authors Jos Eggermont and Roland Schaette report, in respective chapters, research involving animals and humans. Studies identify physiological mechanisms of loudness and sound-provoked pain perception that remain only partially understood, but whose existence will influence efforts to improve existing assessments and interventions. A group effort from Larry Roberts, Tanit Sanchez, and Ian Bruce reminds us there is lack of translation between the auditory neuroscience and its clinical community’s application of the science that remains difficult to bridge. Don McFerran’s chapter supports this notion as it comprehensively reviews the inventory of medical diagnoses and associated conditions that have influenced, for better or worse, management of sound intolerance.
The experiences of individuals with reduced sound tolerance is heterogeneous, and can vary on a day-to-day, or hour-to-hour basis. In some individuals tolerance is modulated by emotional and psychological state, personal history of trauma or trauma associations in addition to, or interacting with, the auditory environment. Gerhard Andersson’s history of applying psychological techniques of assessment and management for this patient group provides context to the oftentimes uneasy marriage of cross-disciplinary care. Similarly, as pointed out by Melissa Papesh and her co-authors, auditory-processing changes associated with traumatic brain injury require management that challenges standard audiologic rehabilitation.
Tools to assess the extent and severity of loudness tolerance symptoms are crude, and in some cases may be deeply uncomfortable for the patient, as may be the case in some methods of ascertaining the threshold of loudness discomfort using sound stimulation. Because patients with sound intolerance issues express unique impairments and aversions, the need to assess the patient’s self-assessed condition accurately requires validated intake instruments that are both comprehensive and specific. Kathryn Fackrell and Derek Hoare have each collaborated on intake and evaluation forms for sound-related disorders; their chapter addresses the development and use of these essential diagnostic components. Glynnis Tidball reviews audiologic measures that, while imperfect, remain in use and that, when interpreted reasonably, provide value to an intervention’s use and monitoring.
At present, the literature offers little in the way of hard evidence regarding therapy, and which interventions might be optimal for which type of symptoms or patients. Enriching or enhancing the patient’s auditory environment supports improvements in tolerance as well as accuracy monitoring the dynamic sound world. Grant Searchfield and Caroline Selvaratnam provide suggestions for hearing aid fitting approaches and clinical results that indicate the potential benefits of appropriately-fit devices for even the least tolerant patients. Influences of sound intolerance on pediatric patients remains underreported and poorly understood, however many relevant examples and interventions may be accessed, as indicated in the chapter by Veronica Kennedy and her co-authors. Also included is a chapter by musician and music engineer Rob Littwin. His is the story of a patient who received over many years information of mixed accuracy and effectiveness from many sources as he strove to recover from a dramatic, and career-threatening change in sound tolerance. His chapter includes specific listening regimens intended to change tolerance limits through the use of measured and safe sound experiences. Mr. Littwin’s history of sound recording gives a unique perspective to his experiences as a patient and as a seeker of solutions.
David M. Baguley
Patterson R. Auditory warning sounds in the work environment. Philos Trans R Soc Lond B Biol Sci. 1990;327(1241):485-92
Vastfjall D, Bergman P, Sköld A, Tajadura A, Larsson P (2012) Emotional Responses to Information and Warning Sounds. J Ergonomics 1:106. doi:10.4172/2165-7556.1000106