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Amplification systems: Hearing aids

Amplification systems: Hearing aids. May be analog or digital Consists of a microphone, amplifier, and loudspeaker. Earlier: Linear. Now, compressive with automatic gain control Directional microphones

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Amplification systems: Hearing aids

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  1. Amplification systems: Hearing aids May be analog or digital Consists of a microphone, amplifier, and loudspeaker. Earlier: Linear. Now, compressive with automatic gain control Directional microphones Different types of hearing aids: Body level, BTE, ITE, ITC, CIC, Bone-conduction, Eyeglass, disposable, CROS. http://www.nidcd.nih.gov/health/hearing/hearingaid.htm#4 http://www.ahaanet.com/hearingaidstyles.asp

  2. Hearing aid characteristics • OSPL • Gain: • Full on gain versus reference test gain • Functional gain versus insertion gain • Frequency response • Distortion • Battery drain, equivalent input noise level

  3. Implants Bone-conduction implants http://products.cochlearamericas.com/baha/introduction-to-baha-baha-and-natural-hearing Middle ear implants http://www.hearingcenteronline.com/newsletter/august00c.shtml Auditory brainstem implants http://www.earinstitute.org/news/facts/abifact.htm

  4. Cochlear implants Direct stimulation of the auditory nerve http://www.nidcd.nih.gov/health/hearing/coch.asp http://www.mayoclinic.com/health/medical/IM02586 • Consists of external and internal units. • External: Microphone that picks up acoustic signals, converts it to electrical signals and feeds it to a speech processor. Speech processor then delivers these coded signals to a transmitter, which converts it to magnetic impulses • Internal: Receiver and electrode array. Candidacy issues: Age, hearing loss

  5. Cochlear implant

  6. Issues in amplification Candidacy: Should depend on individual’s specific needs. Goal of amplification: To restore sensitivity, clarity (in quiet and noise) and to prevent amplification to intolerable levels. Earlier: Comparative methods Now: Prescriptive methods Verification of hearing aid performance very important. Compensate for insertion loss. Real ear measures.

  7. Assistive listening devices Allows the signal to be closer to the amplification system. Interface can be FM, infrared, or electromagnetic coupling . Other types: For awareness. Example: Visual or vibrotactile devices.

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