Comparison Test of Phonak SmartLink FM transmitter vs Comfort Digisystem Microphone DM10

Transcription

1 Comparison Test of Phonak SmartLink FM transmitter vs Comfort Digisystem Microphone DM10 Project Report, Nov 2011 Sergey Smirnov, PhD student Department of Electrical and Information Technology Lund University 1

2 1 3 HATS 1. Test Setup and Environment Speech output OUT 1 IN 5 B&K Microphone with preamplifier Hearing Aid 4 OUT 2 Noise output 2 Distance between source and HATS = 1.8m Computer with B&K software and Matlab 6 2

3 Test Layout 1.8 m 3

4 1 Head and Torso Simulator (HATS) [1] HATS Positioning HATS is placed in the middle of a standard office room 4.2mx3.5m. Artificial mouth Frequency spectrum of mouth is calibrated and frequency compensated at Mouth Reference Point (MRP) to be flat between 100 Hz and 10 KHz. The normal speech level is calibrated to be 65 db SPL one meter in front of the artificial mouth. 4

5 2 Nor276 Dodecahedron Loudspeaker [2] 5

6 3 Systems Under Test Two systems are used in the measurements with 3 different hearing aids: - Phonak SmartLink FM transmitter [6] - Comfort Digisystem Microphone DM10 with headset [7] Phonak SmartLink is placed on the HATS chest 20 cm below the MRP. Comfort Digisystem Microphone DM10 is placed on the HATS chest and connected to the headset. The headset of the DM10 system is placed on the right HATS ear. The headset's microphone is located 5,5 cm from the artificial mouth. 6

7 Phonak SmartLink FM transmitter Positioning 7

8 Comfort Digisystem Microphone DM10 Positioning (I) 8

9 Comfort Digisystem Microphone DM10 Positioning (II) The measurements for Comfort Microphone DM10 have been done with the headset in a typical position microphone is 5.5 cm from the artificial mouth (Figure 1) Figure 1 9

10 4 Hearing Aids The following hearing aid has been used in the measurements: - Phonak Exelia Arts [9] Hearing aid has been connected to the transmitting devices and placed in a separate room. The volume of the hearing aid is adjusted after connection to produce similar amplitude characteristics of the recorded speech. 10

11 5 Microphone - B&K free-field microphone with pre-amplifier and Nexus Conditioning Amplifier 2692c [8] have been used to record speech signals coming out from the hearing aids. - Hearing aid and microphone have been connected by plastic tubing and covered by the absorbents (acoustic foam) in order to decrease an influence of surround. 11

12 6 Computer with PULSE software and Matlab Bruel & Kjaer s PULSE platform for and vibration analysis [4] Matlab Software [10] 12

13 Test Speech and Noise Signals 3 test speech signals have been used for measurements - Real speech, multiple speakers from TIMIT database [13] - Artifical female speech, ITU-T P.50 standard [11] - Artifical male speech, ITU-T P.50 standard Babble [14] and ICRA from ICRA- CD [12] have been used as signals. The signals are A-weighted and calibrated to be 0 db one meter in front of the artificial mouth, then the is scaled to produce -10, -5, 0 (no scaling applied), 5, 10 and 15 db SNRs at the reference point 1 meter from the artificial mouth. 13

14 Test Procedure 1) Speech calibration is done. 2) A hearing aid is connected to a transmitting device and placed in a separate room. 3) Hearings aid and recording microphone are connected by plastic tubing and covered by the absorbents (acoustic foam). 4) The volume of the hearing aid is adjusted if required. 5) Speech signals are played through the artificial mouth without and with the at different SNRs through loudspeaker [2]. Simultaneously, the output signal from the hearing aid is recorded. 14

15 2. Speech Quality Measures Perceptual evaluation of speech quality (PESQ) is used to assess speech quality as defined in ITU-T P (wideband, sample rate 16kHz) standard [5]. At high SNRs (10, 15 db) PESQ occasionally fails to align properly the reference and output signals and, therefore, provides incorrect unreliable MOS values. These values have been removed from the final plots. 15

16 PESQ Wideband MOS-LQO Mean Results, Phonak Exelia Arts 2,5 2 1,5 1 ComfortAudio DM-10 Phonak SmartLink 0,5 0 silence babble - 10dB babble - 5dB babble 0dB babble 5dB babble 10dB - 10dB - 5dB 0dB 5dB 10dB 15dB Phonak Exelia Arts 16

17 3. SNR Mean Results SNRs are calculated on the output noisy speech signal from the hearing aids (on the receiving end). 17

18 SNR Mean Results, Phonak Exelia Arts SNR ComfortAudio DM-10, db SNR Phonak SmartLink, db babble - 10dB babble - 5dB babble 0dB babble 5dB babble 10dB babble 15dB - 10dB Phonak Exelia Arts - 5dB 0dB 5dB 10dB 15dB 18

19 4. Segmental SNR Mean Results Segmental SNRs are calculated on the output noisy speech signal from the hearing aids (on the receiving end). 19

20 Segmental SNR Mean Results, Phonak Exelia Arts Segmental SNR ComfortAudio DM-10, db Segmental SNR Phonak SmartLink, db 0-5 babble -10dB babble -5dB babble 0dB babble 5dB babble 10dB babble 15dB -10dB -5dB 0dB 5dB 10dB 15dB -10 Phonak Exelia Arts 20

21 Conclusions Phonak SmartLink FM transmitter and Comfort Digisystem Microphone DM10 have equal speech quality in free conditions (no is added). However, with the presence of, SmartLink s speech quality drops faster with decreasing SNRs Comfort Digisystem Microphone DM10 has better SNRs and segmented SNRs in noisy conditions 21

22 References [1] Head and Torso Simulator [2] Noise Source Hardware, Nor276 Dodecahedron Loudspeaker, from Norsonic [3] LAN-XI data acquisition hardware (Type 3160-B-042) [4] PULSE platform for and vibration analysis [5] ITU-T P.862: Perceptual evaluation of speech quality (PESQ): An objective method for end-to-end speech quality assessment of narrow-band telephone networks and speech codecs [6] Phonak SmartLink FM transmitter, [7] Comfort Digisystem Microphone DM10, [8] Nexus Conditioning Amplifier 2692-c rs/2692c.aspx 22

23 [9] Phonak Exelia Arts, [10] Matlab, [11] ITU-T P.50, [12] ICRA CD, [13] TIMIT database, [14] SPIB Infobases, 23