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Hearing Aids (HA)

Hearing Aids (HA). Or technology to the rescue Upcoming Talk: Isabelle Peretz Musical & Non-musical Brains Nov. 22 @ 12 noon + Lunch Rm 2068B South Building. Finishing up with Tinnitus. One last method of treatment Tinnitus retraining therapy

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Hearing Aids (HA)

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  1. Hearing Aids (HA) Or technology to the rescue Upcoming Talk: Isabelle Peretz Musical & Non-musical Brains Nov. 22 @ 12 noon + Lunch Rm 2068B South Building

  2. Finishing up with Tinnitus • One last method of treatment • Tinnitus retraining therapy • Habituation to tinnitus sound to reduce aversiveness

  3. HA Basics • BTE • Behind the ear • ITE • In the ear • ITC • In the canal • CIC • Completely in canal

  4. HA History • Ear trumpets • Prehistoric • Hollowed ram horns • Speaking tubes (17th century) • Direct sound from mouth • Aurical Aids • In-ear, around ear • Limited frequency range • Effective at less than 1000 Hz • Artificial ear drums (19th century) • Perforated ear drum • Try to insert rubber, cotton or dermal layer • Wire attachment to ossicles • Ineffective

  5. Early Electronic HAs • Carbon-based (early 20th century) • Carbon microphone • Sound  Diaphram: moves carbon globules • Motion of carbon in electric field creates current • Gain 30 dB SPL • Problems • Static, no additional amplification • Bulky, large battery • Benefits • Greater frequency range (500 – 2000 Hz) • Vacuum Tube (circa 1920) • Multiple vacuum tubes response to current in microphone • Problems • Expensive, Multiple batteries, bulky • Benefits • Powerful (up to 140 dB SPL gain)

  6. Analogue Technology (75% sold) • HA: no more vacuum tubes by 1953 • Transistors introduced 1952 • Transistors: Cheaper to produce, much less energy required, equal power • Head-mounting • Eye-glass, Barrettes • Allowed for integrated circuits • Multiple transistors & resistors in same area • Benefits • Cheaper, less bulky, improved frequency range • Problems • No signal processing • All linear changes in amplification

  7. HAs Design • Microphone  Amplifier  High/Low pass filters  Attenuators  Adder  Variable gain amplifier  speaker (output)

  8. Digital HAs (25%) • Convert analogue signal to digital • Advantages • Much greater capacity for signal processing • Preprogrammed environments • Less energy consumption • Lighter • Cheaper to produce • Problems • Programmability?

  9. HA Effectiveness • HOH Population 40% neutral or dissatisfied with HA (Cochran, 2002) • No difference between Digital & Analogue • Problems • Battery 100 hrs (1 week to 10 days) • Will run out, must be replaced/recharged • Limited benefit in noise • Best if 1 meter or less

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