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

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

HA Basics BTE  Behind the ear ITE  In the ear ITC  In the canal CIC  Completely in canal

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

Early Electronic HAs Carbon-based (early 20 th 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)

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

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

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?

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