CSD 5400 REHABILITATION PROCEDURES FOR THE HARD OF HEARING Educational Management of Hard- of-Hearing and Deaf Children Assistive Listening Devices

Communication Needs Addressed by ALDs Face-to-face communication Home, medical treatment, church, restaurants Broadcast and other electronic media Radio, tv, movies, plays and theater Telephone conversations Sensitivity to alerting devices and environmental signals Doorbells, smoke alarms, telephone, alarm clocks

Noise Any unwanted or unintended sound that masks or renders inaudible the signal Ambient noise Background noise Signal-to-noise ratio dB unit

Reverberation An acoustic phenomenon caused by sound rebounding off the surfaces of an enclosure and physically interfering with the original signal Causes masking of the original signal and temporal smearing Reverberation time

When Reverberation and Background Noise Co-exist Finitzo-Hieber & Tillman (1978) Speech recognition scores of 12 normally hearing and 12 hearing impaired kids in different listening conditions

Assistive Listening Devices ALDs work by collecting sound from the sound source and delivering it to the user’s ear

Categories of ALDs Hardwire units The sound source and the listener are physically connected by a wire Listener is “tethered” to the sound source Direct audio input Pocket talkers Older systems Wireless units

Wireless Units Sound is transmitted from the sound source to the listener by means of radio waves (FM), infrared signals, or an induction loop system

Infrared Systems Sound is transmitted using a light signal Transmitter/emitter Photo detector diode Must be used indoors Theaters Places of worship

Induction Loop Systems Sound is transmitted by electromagnetic signals picked up by a listener’s personal hearing aid via a telecoil switch Theaters, classrooms, meeting rooms, places of worship Rather inexpensive, but can be plagued with technical problems

FM Systems Radio (FM) waves are used to transmit sounds from the source to the listener The most common system used in the classroom setting Microphone, transmitter, receiver

Benefits of the FM System S/N is improved The effects of reverberation are eliminated Both speaker and listener are not tethered (hardwired) FM signals can penetrate boundaries

Soundfield FM System Signal is delivered to loudspeakers set up around the room via FM transmitter Equipment isn’t child-specific Hard of hearing child isn’t singled out What kind of difference can this make in a “regular” classroom?? Hermantown Classroom FM study