1. Assistive Devices Objectives Describe effects of FM system on speech perception Recommend appropriate assistive listening devices for a given child.

2. Assistive Devices - FM ANSI Standard 12.60 - Classroom acoustics Noise no greater than 30 dB-A Reverberation time (RT60) no greater than 0.6/0.7 s

3. Assistive Devices - FM 60 dB room noise 4’ away: 66 dB +6 SNR 8’ away: 60 dB 0 SNR 16’ away: 54 dB -6 SNR

4. Assistive Devices - FM Mic 1’ to mouth 60 dB room noise 1’ away: 78 dB +18 SNR 1’ away: 78 dB +18 SNR 1’ away: 78 dB +18 SNR

5. Assistive Devices - FM Types Microphones Lavalier Boom Handheld Receivers Self contained Direct audio input to CI or HA Induction Neckloop T-Coil

6. FM Microphone Styles

7. FM Receivers

8. Soundfield FM

9. Desktop FM

10. Conundrum of the FM v. HA/CI Microphone FM only – only teacher’s voice is audible FM+Mic – teacher plus environment audible For severe/profound loss, also own voice is audible

11. Adaptive FM FM system automatically adjusts level of hearing aid/CI microphone Subjectively preferred Better performance on speech recognition (Thibodeau 2010)

12. Troubleshooting FM Transmitter and receiver must be on same channel Both need to be charged Cables need to be connected

13. Bluetooth adapters Music Music or

14. Other ALDs Closed/open captioning Vibrating alarm clocks Flashing alerts phone, doorbell Amplified telephone Phone relay Voice Carry-Over TTY relay IM relay (AT&T and AOL Instant Messenger)

15. Factors affecting classroom understanding

16. Signal to noise ratio Affected by Noise and Distance

17. Critical distance Where indirect sound level equals direct sound level Indirect energy Direct energy

18. Within 1/3 of critical distance Direct energy 10 dB above indirect Within 1/3 of critical distance Critical distance

19. Beyond 3x critical distance Direct energy 10 dB below indirect More than 3x the critical distance Critical distance

20. Directional microphones are only effective within critical distance!! Critical distance