Micromeritics - Fundamental and Derived Properties of Powders
FMs and ALDs
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
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)