title: Over-the-Counter Hearing Aids: A Lost Decade for Change.
abstract: BACKGROUND
  Hearing aids sold directly to consumers in retail stores or through the internet, without individual prescription by audiological professionals, are termed over-the-counter (OTC) devices. This study aimed to determine whether there was any change in the electroacoustic characteristics of OTC devices compared to research carried out a decade earlier. The previous results indicated that most OTC devices were low-frequency-emphasis devices and were unsuitable for elderly people with presbycusis, who were likely to be the major consumers of these products.
  
  
  METHODS
  Ten OTC devices were selected and their electroacoustic performance was measured. Appropriate clients for the OTC devices were derived, using four linear prescription formulae, and OTC suitability for elderly persons with presbycusis was investigated.
  
  
  RESULTS
  OTC electroacoustic characteristics were similar to those in the earlier study. Most OTC devices were not acoustically appropriate for potential consumers with presbycusis. Although several of the devices could match prescriptive targets for individuals with presbycusis, their poor electroacoustic performance--including ineffective volume control function, high equivalent input noise, and irregular frequency response--may override their potential benefit.
  
  
  CONCLUSIONS
  The low-cost OTC devices were generally not suitable for the main consumers of these products, and there has been little improvement in the appropriateness of these devices over the past decade.
authors.affiliation: Division of Speech and Hearing Sciences, Faculty of Education, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Zoe Yee Ting
authors.initials: ZY
authors.lastname: Chan
authors.affiliation: Division of Speech and Hearing Sciences, Faculty of Education, University of Hong Kong, Pokfulam, Hong Kong.
authors.forename: Bradley
authors.initials: B
authors.lastname: McPherson
mesh_terms: D000158:Acoustic Impedance Tests; D004423:Ear / Q000502:physiology; D019544:Equipment Failure Analysis; D005246:Feedback; D006310:Hearing Aids / Q000145:classification*; D006801:Humans; D008954:Models, Biological; D011304:Presbycusis / Q000628:therapy; D011474:Prosthesis Design