Lecture 14 Flashcards
What are some audiology services that WIDHH provides?
Hearing assessments, hearing aid trials with new technology, speechreading classes, community education, lend an ear program
What is included in the aural rehabilitation model? (4)
Sensory management (hearing loss addressed) Instruction (how to use aids) Perceptual training (software to train you to hear) - improves scores on formal speech perception tests Counselling (how one functions with hearing aids)
Why is hearing assistance technology necessary?
To overcome the difficulties of hearing in adverse listening conditions
To alert individuals to important environmental sounds
What are the main obstacles of everyday listening environments?
Background room noise
Reverberation
Distance
What happens with background noise?
Noise masks the weaker transient consonant phonemes more than the longer and more intense vowels
-80-90% of the acoustic info important for speech perception comes from the consonants
What is signal-to-noise ratio?
What is it in classrooms?
What do children with HL need for SNR?
Level of speech signal relative to the level of noise measured in dB
Classroom environments can range from +5 to-7 dB SNR
Children with SNHL require 10-15dB SNR to achieve the same speech perception as children with normal hearing
What is the critical SNR?
Ratio at which 50% of speech is understood
Critical SNR for normal: -6dB
Critical SNR for severe to profound loss 15-20dB
What are typical classroom noise levels?
Unoccupied: 51-72dB
Teacher’s voice: 65dB
Overall range SNR: -7dB to +5dB
What are some populations that find it difficult to “Listen and Learn”?
Young children <15 years old
History of recurrent otitis media
Language disorder
Articulation disorder
What is reverberation? What is the result of this?
What is RT? When do people start having trouble understanding speech?
What do people with HL need for RT?
The prolongation or persistence of sound within an enclosure when sound waves bounce off hard surfaces
Result is masking or “smearing” of consonants
RT is the time sound decays by 60dB
Start having trouble understanding speech when RT =1.0 sec
HL need 0.4-0.5 sec
What does distance have to do with sound?
What do reflections do?
How can speech recognition be improved?
When distance between speaker and listener is doubled, sound decreases by 6dB (inverse square law)
Early sound reflections reach the listener 50ms after the direct sound; combine with direct sound to increase perceived loudness and intelligibility. Early reflections increase in small, highly reverberant rooms
Speech recognition can be improved by decreasing the distance between the speaker and the listener.
What happens beyond the critical distance of 2-6 m?
Reverberant sound energy dominates
What are some acoustic room modifications that can be made for those with HL?
SNRs should be above +15dB
Unoccupied noise levels should not exceed 30-35 dBA
RTs should not surpass 0.4 seconds
What are some practical room modifications for acoustics?
Acoustic ceiling tiles, carpeting, draperies, glides on chair legs, elevated projector tables, smaller desks (less-sound reflective surface)
Induction loop: how does it work?
Hearing aid switched to the telecoil settings, it detects electromagnetic field from phone or induction loops.
Electromagnetic energy > electrical energy
Electrical energy > acoustic signal
Small speaker and field created around speaker that is emitted around it
What is the telecoil sound quality?
Sound quality is not as ‘clean’ as a direct audio connection
Telecoils generally have a low frequency hum
