Saturday 18 May 2013

BSHAA 18/05/13

BSHAA 17/05/13 pm

UCL Dr David McAlpine

Cocktail Party SNR issues.

Negative SNR possible thru natural hearing.

Separation of signal via brain. Binaural construction of 'sound' at retro-cochlear level. Localization and spatial release from masking noise. 
Social aspect of Binaural hearing.

Duplex theory of binaural hearing. Raleigh et.....
Interaural level dependency: HF
Temporal difference - discovered through phase differential. LF.
Observable binaural beats - phase shifting of diff frequency sound 'rotates' through stereo spectrum.

Binaural - unmasking; invert one signal to lift it from the noise.

Reflected surfaces - don't just use direct paths. Make the signal far more complex.

Integrating info across both ears: binaural presentation essential to tell differences. 

Limits of Binaural Hearing: still front/back issues. Ear localisation - pinna allows boosted signals. You need over a month to adapt to 'new' ears.

Restoration?  Do hearing aids restore binaural hearing? Compression might be an issue - linearity makes things better - FPL.??  

Dr. Todd Ricketts

Hearing aid features.....12 classes of features.

8 minors - Beamforming, Sophisticated Gain Processing, Tinnitus Masking, Bilateral sharing info; spatialization correction, remote mics, Extended HF - related to slope of loss, shallower slope better. Frequency lowering: no average benefit in adults. Trainable algorithms - some px, not all.

4 main areas; A-F grading/Target Px/Manufacturer Differences.

Digital Noise reduction: Gain lowering 
Fast Filtering : takes out noise between speech.
Results - Comfort improved, perceived quality improved - doesn't make SNR worse in adults: but no improvement in SNR. Less listening effort? -6dB not helping.

DNR:  Real World Benefit: C, Application: B+,MFR: SD

FBM performance - phase cancelling etc.
Widened application of hearing aids etc....
Issues - Entrainment, speed, effective magnitude.

Measure REAR using stored probe tube calibration - open fit. Fixed position - does it cause problems? Not with live speech signal.

Big variation in efficacy of FBM systems, lots of variation in gain 
Also variation in speed of FBM - Phone 'chirp'

FBM: RWB A-, App; A+, MFR: LD

Frequency Compression in Mild/Mod losses.
Limited performance  S sound only.
Doesn't hurt that much.


Wireless Routing Capability: Streamer device etc.
Issues with streamers - direct routing to come/battery issues.
Improved SNR etc.
Advantage limited for bilateral open fitted; marginal.
Closed fitting much better. Turn off  outside mic.
Better than telecoil/ bilateral better again.
Positioning issues resolved

Wireless BC/B-/LD.

Mel Ferguson - NIHR

10 million in UK with loss. 70+ years.
20% ITD HA. -£30m wasted.

Auditory Training - Does it work? Improvements - some evidence.
No improvement of speech in noise.

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