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1、 AS 60118.02007 IEC 60118-0 Ed. 2.0 (1983) Includes Amendment 1:1994 Australian Standard Hearing aids Part 0: Measurement of electroacoustical characteristics AS 60118.02007 This Australian Standard was prepared by Committee AV-003, AcousticsHuman Effects. It was approved on behalf of the Council of
2、 Standards Australia on 3 November 2006. This Standard was published on 20 February 2007. The following are represented on Committee AV-003: Association of Accredited Certification Bodies Association of Australian Acoustical Consultants Association of Consulting Engineers Australia Audiological Soci
3、ety of Australia Australasian Faculty of Occupational Medicine Australian Acoustical Society Australian Chamber of Commerce and Industry Australian Council of Trade Unions Australian Industry Group Department of Consumer then adjust the gain control to the reference test gain position. c) Vary the f
4、requency of the sound source over the recommended frequency range 200 Hz to 8 000 Hz, keeping the input SPL constant at 60 dB. d) Repeat the test in c) with the various tone control settings to be tested. e) The frequency responses at the various tone control settings should be plotted together with
5、 the basic frequency response as the ear simulator SPL versus frequency. 7.6 Effect of gain control position on frequency response The purpose of this test is to show the effect, if any, of gain control positions on the frequency response of the hearing aid. 7.6.1 Test procedure: a) Proceed as in It
6、ems a), b) and c) of Sub-clause 7.3.1. b) Adjust the gain control from a full-on position downward in approximately 10 dB steps at the reference test frequency. c) At each setting of the gain control vary the frequency over the recommended range from 200 Hz to 8 000 Hz keeping the input SPL constant
7、. d) The frequency responses at each gain control position should be plotted as the ear simulator SPL versus frequency. 7.7 Characteristics of the gain control The purpose of this test is to determine the characteristic of the gain control and pre-set gain controls, if any, expressed as acoustic gai
8、n relative to full-on acoustic gain, versus mechanical settings of the control. Standards Australia www.standards.org.au 10 7.7.1 Test procedure: a) Turn the gain control full on. b) Adjust the input SPL as in Item b) of Sub-clause 7.3.1. c) Determine the acoustic gain. d) Repeat the test with a suf
9、ficient number of other settings of the gain control to cover the range of the control. e) Plot the acoustic gain relative to the full-on acoustic gain versus settings of the gain control, using a linear scale for the positions of the control. 7.8 Effect on the full-on acoustic gain of variation of
10、battery or supply voltage The purpose of this test is to determine the effect on the full-on acoustic gain of variation of battery or supply voltage. 7.8.1 Test procedure: a) Proceed as in Items a), b) and c) of Sub-clause 7.7.1. b) Repeat the test for various values of the supply voltage within the
11、 specified voltage range for normal operation of the battery. c) Plot the full-on acoustic gain relative to the full-on gain obtained at normal battery voltage versus voltage. 7.9 Effect on the full-on acoustic gain of variation of internal resistance of battery or supply The purpose of this test is
12、 to determine the effect on the full-on acoustic gain of variation of internal resistance of battery or supply. 7.9.1 Test procedure: a) Proceed as in Items a), b) and c) of Sub-clause 7.7.1. b) Repeat the test at a constant supply voltage for various values of the internal resistance within the res
13、istance range of interest for the battery types recommended for the hearing aid. c) Plot the acoustic gain relative to the gain obtained at normal internal resistance versus internal resistance. 7.10 Effect on OSPL90 of variation of battery or supply voltage The purpose of this test is to determine
14、the effect on OSPL90 of variation of battery or supply voltage. 7.10.1 Test procedure: a) Turn the gain control full on. b) Adjust the frequency to the reference test frequency. c) Adjust the input SPL to 90 dB. d) Measure the OSPL90 e) Repeat the test for various values of the supply voltage within
15、 the voltage range for the hearing aid. f) Plot the OSPL90 values relative to the value obtained at normal battery voltage, versus voltage. 7.11 Battery current The purpose of this test is to determine the current drawn from the battery by the hearing aid. www.standards.org.au Standards Australia 11
16、 7.11.1 Test procedure: a) With the gain control in the reference test gain position, measure the battery current at the reference test frequency and at an input SPL of 60 dB. The direct-current measuring system shall have the following characteristics: 1) An accuracy of 5% at the value of current m
17、easured. 2) A direct current resistance not exceeding 50/I, where I is the current being measured, in milliamperes. 3) An alternating current impedance not exceeding 1 over the frequency range 20 Hz to 5000 Hz. NOTE - One method of realizing Item 3 above is to bypass the current meter with an 8 000
18、F capacitor. The capacitor should not shunt the battery or power supply. 7.12 Measurement of amplitude non-linearities in hearing aids The purpose of this test is to determine the degree of the amplitude non-linearity in the sound output under specified conditions. The amplitude non-linearity can be
19、 described by the degree of: a) Harmonic distortion Distortion products are generated, by the action of a non-linear transfer function, at integer multiples of the test signal frequency. The harmonic distortion products appear at frequencies above the input signal frequency. At higher frequencies th
20、e distortion products may fall outside the frequency range of the earphone as measured in the ear simulator. Therefore, at higher frequencies, non-linearity is not sufficiently represented by this measurement. However, for the lower frequency range, the harmonic distortion products give a suitable d
21、escription of the non-linearity. b) Intermodulation distortion Distortion products are generated by the action of a non-linear transfer function on an input signal composed of at least two signals of different frequencies. Intermodulation distortion products, for instance those measured by the diffe
22、rence- frequency distortion method are more sensitive to non-linearity in the higher frequency range than are harmonic distortion products (for further information, see Appendix A). 7.12.1 Harmonic distortion Harmonic distortion is measured using an input signal of one sinusoidal tone having the fre
23、quency f. The distortion products have as frequencies nf, n being an integer. Total harmonic distortion, or harmonic distortion of the nth order, is defined as the ratio of the output sound pressure of the total harmonic distortion products, or at the frequency nf respectively, to the total output s
24、ound pressure and can be expressed as a percentage or in decibels. The total harmonic distortion is given by the formula: 222 234 2222 1234 . . PPP PPPP + + Standards Australia www.standards.org.au 12 and harmonic distortion of the nth order by the formula: 2 2222 1234 . n P PPPP+ where P1 is the so
25、und pressure of the fundamental frequency of the signal in the ear simulator and P2, P3, P4, . Pn, are the sound pressures of the harmonic components of the second, third, fourth . nth order. 7.12.2 Test procedure a) Adjust the gain control of the hearing aid to the reference test gain position. The
26、 position of other controls shall be stated in the report; these should preferably be set to a position that gives the widest bandwidth. b) Vary the frequency of the sound source over the frequency range 200 Hz to 5 000 Hz with an input sound pressure level of 70 dB and analyze the output signal for
27、 levels at the harmonic frequencies nf or record the total harmonic distortion content. The bandwidth of the filter should be stated. For continuous recording the sweep rate shall be such that the response does not differ by more than 1 dB from the steady-state value at any frequency. In the event t
28、hat the response curve rises 12 dB or more between any test frequency and its second harmonic, distortion tests at that frequency may be omitted. NOTE - A total harmonic distortion meter, whose function is described by the first formula of Sub- clause 7.12.1 measures the residue after the fundamenta
29、l component is removed. Thus noise, such as ambient noise in the test space or self-noise in the hearing aid, will appear as a distortion product. The reading of distortion on the distortion-meter should decrease by at least 10 dB when the input signal is turned off. Otherwise, the accuracy of the m
30、easurement will be degraded. c) If required, repeat the procedure described in Item b) with other input sound pressure levels. d) Plot the harmonic distortion versus the frequency of the sound source and/or versus the input sound pressure level. 7.12.3 Intermodulation distortion Difference-frequency
31、 distortion Difference-frequency distortion is measured using an input signal composed of two sinusoidal signals f1 and f2 having amplitudes within 1.5 dB of each other, f2 being higher in frequency than f1 The levels of the second order (f2 f1) and the third order (2 f1 f2) distortion products shal
32、l be measured and expressed as a percentage or in decibels referred to the output level of f2. Higher order components may also be measured. 7.12.3.1 Test procedure a) Adjust the gain control of the hearing aid to the reference test gain position. The position of other controls shall be stated in th
33、e test report. b) Adjust the frequencies of the test signals f1 and f2 such that f2 f1 = 125 Hz. NOTE - Frequency differences other than 125 Hz may be appropriate and when used the frequency difference should be stated, for example if the signal-to-noise ratio is too low at 125 Hz, a higher frequenc
34、y difference may be used. c) Select a suitable number of frequencies f1 and f2 of the sound source or sources within the frequency range 350 Hz to 5 000 Hz, maintaining the selected difference frequency and keeping the sound pressure level of each of the two test tones at 64 dB. Measure the sound pr
35、essure levels at the frequencies f2 f1 and 2f1 f2 with a suitable filter. The output level at the filter terminals should decrease by at least 10 dB when the test signal f2 is switched off. The bandwidth of the filter should be stated. d) If additional information with respect to input level is deem
36、ed to be significant, repeat the procedure described in Item c) at other appropriate input levels. www.standards.org.au Standards Australia 13 e) Plot the difference-frequency distortion products as two curves or tabulate them for each input level, one for the second order, and one for the third ord
37、er products as a function of the higher frequency f2. NOTE - Although the upper limit of the frequency range is restricted to 5 000 Hz, it is recognized that a considerable amount of intermodulation distortion may occur at input frequencies higher than 5 000 Hz. 7.13 Effect on amplitude non-linearit
38、ies of variation of battery or supply voltage and internal impedance The purpose of this test is to determine the effect on the amplitude non-linearity of variation of battery or supply voltage and of variation of internal impedance of the battery or the power supply. Repeat the procedure described
39、in Sub-clause 7.12 using appropriate battery or supply voltages within a range stated by the hearing aid manufacturer. 7.14 Internal noise generated in the hearing aid The internally generated noise in the hearing aid can be measured in a simple manner as described in Sub-clause 7.14.1, or, alternat
40、ively analyzed in third-octave bands, as described in Sub-clause 7.14.2. The method used shall be reported with the results. 7.14.1 Simplified method With this method, the internally generated noise is expressed as an equivalent input noise level. The ambient noise in the test space shall be negligi
41、ble. NOTE -Without measuring the spectrum of the ambient noise in the test space, as in the third-octave band method, it is difficult to assess its contribution to the total noise level measured in the ear simulator. Therefore, care should be taken to ensure that this ambient noise does not influenc
42、e the test results. 7.14.1.1 Test procedure a) Adjust the gain control of the hearing aid approximately to the reference test gain position. For the purpose of this test a precise position of the gain control is not required. The position of other controls shall be stated in the test report. b) Meas
43、ure the output sound pressure level Ls in the ear simulator at the reference test frequency with a pure-tone input sound pressure level L1 of 60 dB. NOTE - For automatic gain control (AGC) hearing aids, an input sound pressure level of 60 dB may be too high and should be reduced to a lower level whi
44、ch ensures essentially linear input/output conditions. In this case, the input sound pressure level should be stated. c) Switch off the sound source and measure the sound pressure level L 2 in the ear simulator caused by the internally generated noise. To determine that the noise in the ear simulato
45、r and the ear simulator microphone system is adequately low, the measured noise should decrease by at least 10 dB when the hearing aid is turned off. d) Calculate the equivalent input noise level LN as follows: LN = L2 (Ls L1) where: L2 is the sound pressure level in the ear simulator as measured in
46、 Item c) Ls is the sound pressure level in the ear simulator at the reference test frequency as measured in Item b) L1 is the input sound pressure level at the reference test frequency (60 dB) 7.14.2 Third-octave band analysis method With this method the internally generated noise as a function of f
47、requency is expressed in terms of the equivalent input sound pressure level in third-octave bands (see IEC 60225: Octave, Half-octave and Third-octave Band Filters Intended for the Analysis of Sounds and Vibrations). Standards Australia www.standards.org.au 14 7.14.2.1 Test procedure a) With the sou
48、nd source switched off, the sound pressure level of the ambient noise in the test space shall be measured in third-octave bands with centre frequencies lying in the frequency range 200 Hz to 5 000 Hz. The ambient noise level in the test space shall be at least 10 dB below the equivalent input noise
49、level as calculated in Item e). b) Adjust the gain control of the hearing aid to the reference test gain position as described in Sub-clause 7.14.1, using the third-octave band filter centred at 1 600 Hz. c) With the sound source switched off, measure the sound pressure level of the output noise in the ear simulator for third-octave bands with centre frequencies in the range 200 Hz to 5 000 Hz (Figure 1a, page 45). To determine that the no