1 - AS 1088.0-1987 HEARING AIDS - MEASUREMENT OF ELECTROACOUSTICAL CHARACTERISTICS
4 - PREFACE
5 - CONTENTS
6 - 1. Scope
6 - 2. Object
7 - 3. General conditions
7 - 4. Explanation of terms
7 - 4.1 Ear simulator
7 - 4.2 Substitution method
7 - 4.3 Comparison method
7 - 4.4 Pressure method
7 - 4.5 Simulated in situ method
7 - 4.6 Reference orientation (of a hearing aid)
8 - 4.7 Reference point (of a hearing aid)
8 - 4.8 Test point
8 - 4.9 Supply voltage
8 - 4.10 Acoustic gain
8 - 4.11 Full-on acoustic gain
8 - 4.12 Maximum acoustic gain at a specified frequency
8 - 4.13 Saturation sound pressure level
8 - 4.14 Maximum saturation sound pressure level
8 - 4.15 Output sound pressure level for an input sound pressure level of 90 dB (OSPL90) at a specified frequency (or frequencies
8 - 4.16 Reference test frequency
9 - 4.17 Reference test gain control position
9 - 4.18 Reference test gain
9 - 4.19 Frequency response
9 - 4.20 Comprehensive frequency response curves
9 - 4.21 Basic frequency response curve
9 - 4.22 Steady state input-output graph
9 - 5.Test equipment
9 - 5.1 Acoustical requirements for the test enclosure
10 - 5.2 Sound field at the test point
10 - 5.3 Ear simulator
10 - 5.4 Equipment for the measurement of sound pressure level in the ear simulator
11 - 5.5 Equipment for automatic sweep frequency recording
11 - 5.6 Calibration of free-field sound pressure level
11 - 6. Test conditions
11 - 6.1 Choice of test point
12 - 6.2 Calibrating the sound field
12 - 6.3 Locating the hearing aid for tests
13 - 6.4 Normal operating conditions for the hearing aid
14 - 7. Measurements
14 - 7.1 Maximum saturation sound pressure level
14 - 7.2 Output sound pressure level frequency response for an input SPL of 90 dB
15 - 7.3 Full-on acoustic gain frequency response
15 - 7.4 Comprehensive frequency responses and basic frequency response
16 - 7.5 Effect of tone control position on the basic frequency response
16 - 7.6 Effect of gain control position on frequency response
17 - 7.7 Characteristics of the gain control
17 - 7.8 Effect on the full-on acoustic gain of variation of battery or supply voltage
17 - 7.9 Effect on the full-on acoustic gain of variation of internal resistance of battery or supply
18 - 7.10 Effect on OSPL90 of variation of battery or supply voltage
18 - 7.11 Battery current
18 - 7.12 Measurement of amplitude non-linearities in hearing aids
21 - 7.13 Effect on amplitude non-linearities of variation of battery or supply voltage and internal impedance
21 - 7.14 Internal noise generated in the hearing aid
22 - 7.15 Characteristics of hearing aids with induction pick-up coil input
24 - 7.16 Characteristics of hearing aids with automatic gain control circuits
24 - 8. Frequency response recording chart
25 - APPENDIX A - HARMONIC AND INTERMODULATION DISTORTION