Possibilities for the evaluation of the benefit of binaural algorithms using a binaural audio link

Transcription

1 Possibilities for the evaluation of the benefit of binaural algorithms using a binaural audio link Henning Puder Page 1

2 Content Presentation of a possible realization of a binaural beamformer iscussion of various methods for beamformer performance evaluation Page 2

3 Beamforming: Target Maximum possible attenuation of interfering sources around the head when a source from the frontal direction is present at the same time. Target: chieve a more narrow frontal beam db db db Signal frequency: f = 1 khz Omni directional setting ifferential beamformer Page 3

4 Beamforming audio streaming Processing Monaural Processing Monaural Processing Processing data exchange Page 4

5 Freq. nalysis Monaural Beamformer Restauration of Spatial Cues Beamforming, Ref:[1] Beamformer Noise reduction Head movement Signal transmission between the hearing aids compensation Page 5

6 Freq. nalysis Monaural Beamformer Restauration of Spatial Cues Beamforming Beamformer Target Noise reduction Signal transmission between the hearing aids Target and Noise estimation Head movement daptive compensation Noise Cancellation Mon. Output Interferer reference: Interferer Page 6

7 Freq. nalysis Monaural Beamformer Restauration of Spatial Cues Beamforming Target detected at 0 Target detected at +10 Target detected at -10 Beamformer Noise reduction Head movement Signal transmission between the hearing aids compensation Page 7

8 Freq. nalysis Monaural Beamformer Restauration of Spatial Cues Beamforming Beamformer Noise reduction uto-ps Estimation Cross-PS Estimation Head movement compensation X (, ) (, ) (, ) L X t f L SS t f NLN t f L SS ( t, f) W ( t, f ) X (, ) LX t f L Target-PS Estimation ( t SS, f ) Page 8

9 Freq. nalysis Monaural Beamformer Restauration of Spatial Cues Beamforming Beamformer Noise reduction Signal transmission between the hearing aids Head movement compensation Intelligent combination to - preserve interferer cancellation and - restore binaural cues based on mon. output Page 9

10 Evaluation Subjective listening / demo evaluation. Measurements with sequential irectivity Index (si). Studies with test subjects: Speech reception threshold (SRT) measurements Listening effort measurements: Subjective rating procedures Objective EEG-based measurements Page 10

11 Sequential irectivity Index (si) Measurements Ref:[2] esired: No test-settings Include all features related to directionality Get close to realistic use-case Consider target and interferers Observation of Interferer-to-target ratio However: How to separate effects on target and interferer? Page 11

12 Sequential irectivity Index (si) Measurements Perform two consecutive test runs with simultaneous target and interferer. Interferer is altered in phase. Playback: signals target interferer play back first run play back second run symbol Recording: same initial conditionsequal behavior of time-variant processes no phase alteration by signal processing However: works fine for most power/level- based and power-optimizing algorithms like beamforming ssuming pseudo-linear processing of the object under test! Page 12

13 Beamforming Results: Stronger focus to the front direction. More attenuation to the side speakers (e.g. +/- 45 ) Sound examples: Setup: english french japanese Omni directional setting ifferential beamformer beamformer db db 0 db spanish italian Omni-directional signal: beamforming: 180 Page 13

14 SRT measurements: Clinical Study Results, Ref:[3] Target speech and background competing signal material using Oldenburg Satztest (OLS), Ref:[4], for site1 and Hearing-In-Noise Test (HINT) material used for site 2, Ref:[5] 1 meter Background competing signal with also OLS/HINT sentences presented (uncorrelated) from 7 loudspeakers with gaps between sentences removed dditional speech babble was added at 15 db below the sentences. Background noise was constant at 72 db SPL Setup Page 14

15 SRT measurements: Clinical Study Results, Ref:[3] SRT improvement by binaural beamformer compared to omni: approx. 5 db ~ 5dB SRT advantage compared to Normal listeners: approx db ~ 5dB > 2.5dB > 2dB Standard presentation and scoring methods for both the OLS and the HINT were used. t both sites, a speech-in-noise test was administered to allow for calculation of the 50% correct point for speech recognition. Site 1: OLS (Oldenburger Satztest) mean normal hearing age group (n=15) was 64.5 and (n=29) 68.8 for the hearing impaired group. Site 2: HINT (Hearing In Noise Test) mean normal hearing age group (n=14) was 58.8 and 65.8 (n=14) for the hearing impaired group. Page 15

16 Listening Effort Listening Effort Study Results, Ref:[6] Subjective listening effort (LE) evaluation for 9 HI subjects 9 HI subjects: - mean age 68 years, - 4FHL: 57 db Individual target level adjustment for 80% correct word scoring in Omni setting Listening effort decreased in mean from Considerable to Little effort P=0.001 Extreme effort Very much effort Considerable effort Moderate effort Little effort Very little effort Omni beamforming No effort Page 16

17 Listening Effort Listening Effort Study Results, Ref:[6] Evaluation of listening effort (subjective ratings) at -3.5 db SNR comparing NH and HI test persons. Spread of the LE results in relation to the HL. Extrapolation of the fitted curve indicates a lower listening effort for NH persons with the beamformer. Page 17

18 Listening effort: Subjective rating and objective EEG based listening evaluation, Ref:[7,8] Evaluation with hearing impaired persons: Benefit of Narrow irectionality 60% improvement (site 3, p=0.04) 37% (site1) and 40% (site 3, p = 0.05) reduction in listening effort EEG based Evaluation Subjective Rating Site 1: Hearing and ging Research Laboratory (HRL), University of Iowa, Iowa City, I, US Site 3: National coustic Laboratories (NL), Sydney, ustralia Page 18

19 Listening effort: Subjective rating and objective EEG based listening evaluation, Ref:[7] Evaluation compares normal hearing persons and hearing impaired using Narrow irectionality => Listening effort for hearing-impaired individuals essentially the same as for individuals with normal or near-normal hearing for the same speech-innoise task EEG based Evaluation Subjective Rating Page 19

20 Listening effort: Subjective rating and objective EEG based listening evaluation, Ref:[7] Individual person s results: - Results show a continuously decreasing objective listening effort - Overall increase of recognition rates; some subjects profit already from monaural, some more from binaural technology. Subject 1 Subject 2 Page 20

21 Processing: utomatic Control For a natural listening experience: Important to activate and set the strength of the binaural beamformer in relation to the listening situation. Based on several measures such as Classifier decision Input signal level Noise floor level ominant speech signal direction the appropriate beamformer setting is chosen. Only when necessary, the binaural beamformer is activated (optimized power consumption). Page 21

22 Summary Presentation of an example of binaural hearing aid technology Evaluation results based on si measurements SRT improvements and SRT comparisons with NH persons Listening effort measurements using EEG based evaluations and Subjective effort ratings Page 22

23 References [1] H. Kamkar-Parsi, E. Fischer, & M. ubreville (2014). New Strategies for Enhanced Hearing. Hearing Review, 21(10), [2] M. ubreville & S. Petrausch, "irectionality assessment of adaptive binaural beamforming with noise suppression in hearing aids," 2015 IEEE International Conference on coustics, Speech and Signal Processing (ICSSP), South Brisbane, QL, 2015, pp [3] T. Powers & M. Froehlich (2014). Clinical Results with a New Wireless irectional Hearing System. Hearing Review, 21(11), [4] B. Kollmeier & M. Wesselkamp(1997). evelopment and evaluation of a German sentence test for objective and subjective speech intelligibility assessment. J. coust. Soc. m.,102(4), [5] M. Nilsson, S.Sol, J. Sullivan(1994). evelopment of the Hearing in Noise Test for the measurement of speech reception thresholds in quiet and noise. J. coust. Soc. m., 95(2), [6] J. Mejia, L. Carter, H. illon, V. Littmann: Listening Effort, Speech Intelligibility, and Narrow irectionality. Hearing Review. 2017;24(1):22. [7] V. Littmann, YH. Wu, M. Froehlich, T. Powers: Multi-center evidence of reduced listening effort using new hearing aid technology. Hearing Review. 2017;24(2): [8] C. Bernarding,. J. Strauss, R. Hannemann, H. Seidler, and F. I. Corona-Strauss, Objective assessment of listening effort in the oscillatory eeg: Comparison of different hearing aid configurations, in Conf Proc IEEE Eng Med Biol Soc, 2014, pp Page 23