IEC TS 62886:2016
(Main)Electroacoustics - Hearing aids - Method for measuring electroacoustic performance up to 16 kHz
Electroacoustics - Hearing aids - Method for measuring electroacoustic performance up to 16 kHz
IEC TS 62886:2016(E) which is a Technical Specification, describes a coupler and measurement methods to characterise the electroacoustic performance of hearing aids and insert earphones primarily in the range of 8 kHz to 16 kHz.
General Information
Standards Content (Sample)
IEC TS 62886 ®
Edition 1.0 2016-08
TECHNICAL
SPECIFICATION
colour
inside
Electroacoustics – Hearing aids – Method for measuring electroacoustic
performance up to 16 kHz
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IEC TS 62886 ®
Edition 1.0 2016-08
TECHNICAL
SPECIFICATION
colour
inside
Electroacoustics – Hearing aids – Method for measuring electroacoustic
performance up to 16 kHz
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 17.140.50 ISBN 978-2-8322-3620-8
– 2 – IEC TS 62886:2016 IEC 2016
CONTENTS
FOREWORD . 5
INTRODUCTION . 7
1 Scope . 8
2 Normative references. 8
3 Terms, definitions and abbreviated terms . 8
3.1 Terms and definitions . 8
3.2 Abbreviated terms . 9
4 Mechanical design of the 0,4 cm coupler . 9
4.1 General . 9
4.2 Cavity dimensions . 10
4.2.1 Critical dimensions . 10
4.2.2 Effective coupler volume . 10
4.2.3 Diameter of the coupler cavity . 11
4.3 Verification procedure of the effective coupler volume . 11
4.3.1 General . 11
4.3.2 Test set-up . 11
4.3.3 Effective volume of the coupler under test . 11
4.4 Measuring microphone . 12
4.4.1 General . 12
4.4.2 Preferred microphone . 12
4.4.3 Alternative microphones . 12
4.5 Static pressure equalisation vent . 12
5 Calibration . 12
5.1 Reference environmental conditions . 12
5.2 Calibration procedure . 13
6 Coupling of receivers and hearing aids to the coupler . 13
6.1 Coupling to a hearing aid receiver by means of tubing . 13
6.2 Coupling to a hearing aid embedded in or connected to an earmould . 13
6.3 Coupling to a receiver in the canal (RIC hearing aid) . 14
6.4 Coupling to a BTE hearing aid with 2 mm continuous internal diameter
tubing . 15
6.5 Coupling to a BTE hearing aid with earmould simulator . 16
6.6 Coupling to a BTE hearing aid with thin tubing . 17
7 Transfer impedance of the 0,4 cm coupler . 18
3 3
8 Comparison of the 0,4 cm , the 2 cm coupler and the occluded-ear simulator . 19
8.1 Sound pressure level frequency response curves . 19
8.2 Comparison of the coupler impedance with typical source impedances . 20
8.3 Influence of sound source impedance on measured level difference between
3 3
the 0,4 cm coupler and the 2 cm coupler . 21
9 Maximum permitted expanded uncertainty for coupler conformance testing . 22
10 Measurements using the 0,4 cm coupler . 23
10.1 General . 23
10.2 Test enclosure and test equipment . 23
10.3 Extended frequency range for total harmonic distortion measurements . 23
10.4 Presentation of data . 24
10.4.1 General . 24
10.4.2 Presentation as 0,4 cm coupler data . 24
10.4.3 Presentation as normalised to 2 cm coupler data . 24
10.5 Maximum permitted expanded uncertainty of measurements performed using
the 0,4 cm coupler . 24
Annex A (informative) Response transforms between the 0,4 cm coupler and the
occluded-ear simulator . 26
A.1 General . 26
A.2 Simulation model of the human ear and approximation of λ/2 resonances . 26
A.3 Measured and simulated transform responses of a standard-fitting . 28
A.4 Transform curves for CIC-fitting and deep-insertion-fitting . 29
Annex B (informative) Measurement and modelling of the transfer impedance of the
0,4 cm coupler . 33
B.1 Measurement procedure . 33
B.1.1 Transfer impedance . 33
B.1.2 Calibration of the volume velocity source at 250 Hz . 33
B.1.3 Calibration of the volume velocity source over the frequency range from
100 Hz to 60 kHz . 34
B.1.4 Test set-up for measuring the coupler transfer impedance . 34
B.2 Measurement of the coupler transfer impedance . 35
B.3 Electrical analogue representation of the coupler as a tube model . 38
Bibliography . 41
Figure 1 – Mechanical design of the 0,4 cm coupler, shown with removable coupling
plate with a nipple for the attachment of coupling tubing . 10
Figure 2 – Coupling to a hearing aid receiver by means of coupling tubing . 13
Figure 3 – Coupling to an ITE hearing aid . 14
Figure 4 – Coupling to a receiver in the canal (RIC hearing aid) . 15
Figure 5 – Coupling to a BTE hearing aid with 2 mm continuous internal diameter
tubing . 16
Figure 6 – Coupling to a BTE hearing aid with earmould simulator . 17
Figure 7 – Coupling to a BTE hearing aid with thin coupling tubing . 18
Figure 8 – Magnitude frequency response of the transfer impedance × frequency and
the related equivalent volume. 19
3 3
Figure 9 – Comparative measurement of the 0,4 cm coupler, the 2 cm coupler and
the occluded-ear simulator frequency responses . 20
Figure 10 – Magnitude frequency responses of acoustic impedance of the 2 cm , the
0,4 cm coupler and various hearing aid types . 21
Figure 11 – Deviation from the normalized coupler volume ratio as a function of the
effective volume of the sound source V . 22
s
Figure A.1 – Electrical analogue model of the human ear . 27
Figure A.2 – Measured transform response of a standard-fitting . 28
Figure A.3 – Comparison between the measured and the simulated standard-fitting
transform response . 29
Figure A.4 – Transform responses for (a) standard-fitting, b) CIC-fitting and (c) deep-
insertion-fitting . 30
Figure B.1 – Test set-up for measuring the coupler transfer impedance . 35
Figure B.2 – Average frequency response of 8 coupler measurements . 35
Figure B.3 – Average transfer impedance of the 0,4 cm coupler . 36
– 4 – IEC TS 62886:2016 IEC 2016
Figure B.4 – Transfer impedance times frequency re 1 Pa/m in dB and as equivalent
volume in mm in the frequency range 100 Hz to 60 kHz . 36
Figure B.5 – Electrical analogue model based on a tube model . 39
Figure B.6 – Comparison between the measured (solid line) and the simulated (dashed
line) transfer impedance . 39
Figure B.7 – Frequency responses of simulated 0,4 cm coupler input and transfer
impedances . 40
Table 1 – Values of U for basic measurements .
...
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