History and Basics of Hearing Aid Amplification

Key Points
  • What and when were the important advances in audiology and technology over time
  • How have these events impacted where we are today?
  • Where are we headed?
  • What are the next challenges?

Timeline: 1800's to 1970

  • 1800 F.C. Rein (first HA manufacturer)
  • 1819 Acoustic Throne
  • 1850's - Ear Trumpet
  • 1876 Bell invented the telephone
  • 1900 - 1st electronic hearing aid
  • 1906 - DeFrost Vacuum tube
  • 1921 - Vacuum tube hearing aid
  • 1937 1st wearable hearing aid
  • 1940 Selective amplification formula
  • 1946 Harvard Report
    • ​this report erroneously stated that most patients perform better with the same frequency response
  • 1947 Transistor
  • 1952 Transistor in hearing aids
  • 1954 Eyeglass hearing aids
  • 1968 directional microphones

Timeline: 1970's - 1980's

  • 1970 Custom products
  • 1975 compression - starting to be automatic
  • 1978 - audiologists dispense hearing aids legally
  • 1979 Skinner - audibility & bandwidth
  • 1980 - Schwartz and Walden - identified the problem in testing as word recognition being unreliable
  • 1981 Studebaker - 845 words to determine a 4% significant difference in word recognition
  • mid 1980's 1st digital
  • 1985 DSL 3.0; 1986 NAL-R
  • 1985 Probe microphone measurement equipment
  • 1985 Wide dynamic range compression implemented
  • 1987 Programable

Timeline: 1990's

  • 1990 Valid, reliable self-evaluation measures
  • 1993 IHAFF calls for three dimensional hearing aid fitting targets
  • 1994 Hearing in Noise testing
  • 1995 First custom digital product
  • 1996 Noise reduction algorithms
  • 1997 Directional and Omnidirectional
  • 1998 RECD
  • 1999 NAL-NL1

Timeline 2000's

  • Digital Benefits
  • 2001 Dead Regions
  • 2002 Adaptive Feedback Control
  • 2002 Probe Mic Signals
  • 2003 Touchless Telecoil
  • 2004 Customizing features
  • 2005 Feedback management systems/open fit/drastic increase in channels
  • 2005 Surge of evidence based practice guidelines (IHAFF)
  • 2005 Expansion as a programmable feature
  • 2006 Wireless communication between hearing aids
  • 2006 rechargeable batteries
  • 2006 built-in FM receiver in several levels of technology
  • 2006 Acceptable Noise Level Test as a predictor
  • 2007 FCC ruling on cell phone compatibility
  • 2007 DSL; NAL-NL2
  • 2007 Wiresless paradigm shift

Timeline 2010-2020

  • 2011 "Wireless" programming
  • 2012 New and improved BiCROS
  • 2012 PSAPs - new and improved
  • 2013 Evidence base for using REAR probe microphone measures to verify audibility
  • 2015 Wearables
  • 2016 Federal interest in benefits of Hearing aids and healthy aging
Catherine Palmer: "No patient should leave a hearing aid fitting without the clinician knowing what SPL is reaching the eardrum and without a clear understanding of the audibility that has been restored across input levels."