INTRODUCTION TO HEARING DEVICES

Transcription

1 INTRODUCTION TO HEARING DEVICES Neuchâtel, June 12 th 2014, Louisa Busca Grisoni CONTENTS 1 NORMAL HEARING (NH) AND HEARING LOSS (HL) 2 HEARING DEVICES 3 SIGNAL PROCESSING IN HEARING DEVICES 4 CONCLUSIONS Page 2 1

2 NORMAL HEARING AND HEARING LOSS Page 4 2

3 PHYSIOLOGIE External - middle- Inner -ear Page 5 PHYSIOLOGIE INNER EAR Page 6 3

4 0.3 nm Very complex micro and nano mechanism Hair cells: inner haircell sensor outter haircell amplifier Page 7 HAIR CELLS Page 8 4

5 Cochlea active sound analyzer! Low frequencies Highfrequencies Helmholtz Piano, 1873 Page 9 NON LINEAR MECHANISM DYNAMIC RANGE Extremly Loud Dynamic range of a bicycle 7:1 Very soft Dynamic range of the ear :1 Page 10 5

6 Bike with a dynamic of: :1 One spin for the whole Tour de France! Page 11 NON LINEAR MECHANISM FREQ. SELECTIVITY Page 12 6

7 HEARING LOSS Hearing Loss (HL) Conductive HL Mixed HL Sensorineural HL Outer Ear Middle Ear Inner ear Retro- Cochlea Central system Page 13 HEARLING LOSS IN DEV. COUNTRIES 1/1000 child is born deaf 17/1000 have some type of hearing loss at 18 Hearing loss in adult population Mild HL Moderate HL Severe HL Profound HL [db HL] [db HL] [db HL] [db HL] 16.9% 4.6% 0.7% 0.2% Page 14 7

8 HEARING LOSS Normal hearing Hearing Loss a o u e i m f sch s w a o u e i m f sch s w Not audible Not audible Frequency khz Frequency khz Page 15 HEARING LOSS Normal hearing Recruitment Loss of frequency selectivity Loss of binaural cues Loss of temporal selectivity Hearing Loss a o u e i m f sch s w Not audible Frequency khz Page 16 8

9 SPEECH UNDERSTANDING IN NOISE Contrast (SNR db) Hearing Loss db Mild hearing loss Moderate hearing loss Severe hearing loss Killion 1997 Page 17 HEARING DEVICES 9

10 TREATMENT OF HEARING LOSS Page 19 Page 20 10

11 BONE ANCHORED HEARING AID (BAHA) How does it work A percutaneous bone screw (3) is inserted into cranium behind ear. An abutment (2) connects sound processor (1) to implanted bone screw (3). Sound is transferred through vibration and is made possible through intimate contact between BAHA system and cranium. What are the limitations? Issues Maximum power output Sound quality, spacial hearing Daily maintenance Trauma (pediatrics) Aesthetics ~5 900 CHF Page 21 ENVOY ESTEEM How does it work? The device is implanted under the skin behind the ear Two leads extend into the middle ear from the device: one to the ear drum to senses movements (sound) and another to delivers a customized dose of energy to the cochlea. Issues De-articulated of ossicular chain Analog Signal processing Surgery is extremely complex, high revision and complications rates ~13 k ~200 units sold annually WW Page 22 11

12 How does a CI works? COCHLEAR IMPLANT Page 23 AdvancedBionics.com Page 24 12

13 COCHLEAR IMPLANT Page 25 Page 26 13

14 SIGNAL PROCESSING IN HEARING DEVICES LOTS OF FEATURES Amplification & Compression RealEar restituting pinna effect NoiseBlock steatdy state noise reduction EchoBlock reverberation canceller WindBlock wind noise reduction SoundRelax impulse noise reduction SoundRecover frequency compression UltraZoom monaural front facing adaptive beamformer SondFlow scene classifier WhistleBlock feedback canceller Stereozomm binaural adaptive beamformer Zoomcontrol flexible directional beamformer DuoPhone audio streaming ear to ear QuickSync bilateral controls Page 28 Fall_Launch_2010_Ambra_GB_Page 28 14

15 BLOCK DIAGRAM HEARING SYSTEM SOUND PROCESSING NO DELAY (<10 MS) NO POWER (< 2MW TOTAL) Sound Pick Up front mic rear mic Analysis Filterbank FFT Analysis Filterbank FFT Sound Cleaning Adaptive Beamformer Real Ear Sound Mic Matching Feedback Cancellation wireless audio + Noise Reduction: Stationary Noise Impulsive Noise Wind Noise Reverberation Environment Classification Environment Detection Steering Output: - Acoustic - Mechanic - Electric. Signal Out Synthesis Filterbank IFFT Gain Calculation (incl. amplitudecompression) Frequency Compression Audibility & Loudness Page 29 DSP SIGNALFLUSS GENERATION I (1996) Page 30 15

16 DSP SIGNALFLUSS GEN II (2000) Page 31 DSP SIGNALFLUSS GENERATION III (2006) Page 32 16

17 DSP SIGNALFLUSS - GENERATION IV (2012) Page 33 17