IEC 60118-1:1999 pdf download – Hearing aids -Part 1: Hearing aids with induction pick-upcoil input

IEC 60118-1:1999 pdf download – Hearing aids -Part 1: Hearing aids with induction pick-upcoil input.
IEC 60118-1 specifies a method of determining the eiectroacoust,c performance of hearing aids fitted with an induction pick-up coil and used in an audio-frequency magnetic field. The Induction pic1-up performance Is measured in a loop simulating conditions of use in room applications
NOTE — Prfrmancq of Induction pick-up cods in telephone mapnei’c fields may ditlaq Lrom rsS*iiis obtained using this standard.
2 Normative references
The following normative documents contain provisions which, through reference In this text. constitute provisions of this part of IEC 60118. At the time of publication, the editions indicated were valid. All normative documents are subject to revision, and parties to agreements based on this part of IEC 60118 are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below. Members of IEC and ISO maintain registers of currently valid International Slandards
IEC 601 18•0:1983, Hearing aids — Part 0; Measurement of electroacoustical characteristics Amendment 1(1994)
IEC 60711:1981, Occluded-ear simulator for the measurement of earphones coupled to the ear by ear inserts
3 DefInitions
Terms and definitions other than those below are specified in lEG 60118-0 and IEC 60711.
3.1
test point
the position at which the strength of the magnetic field is defined
3.2
test space
a space which contains the test point where the hearing aid Is to be placed for testing
3.3
frequency response
the sound pressure level measured in the ear simulator expressed as a function of frequency under specified test conditions
3.4
magneto-acoustical sensitivity
at a specified frequency and under essentially linear inputioutput conditions, the quotient of the Sound pressure in pascals (Pa) produced by the hearing aid in the ear simulator and the magnetic field strength in mA/m at the test point
3.5
magneto-acoustIcal sensitivIty level (MASL)
twenty times the logarithm to the base 10 of the ratio of the magneto-acoustical sensitivity to the reference sensitivity 20 iaPal(I mAim) expressed In decibels
NOTE — To calculat, th, magn,lo-acouztical sensitivity level (MASh Irom measure4nents in this standard tile following IornuIa may be used.
NASh – output SPL —20 Ig mA!mlf dB
whr.
H is the magnetic held strength at the lest point In mAim.
3.6
maxImum magneto-acoustical sensItivIty level
the maximum obtainable MASL, allowing all possible settings of the hearing aid controls
4 Test conditions
4.1 General
Throughout this standard, all Sound pressure levels are relerred to 20 Pa and measured according to lEG 60118-0 and IEC 60711. Magnetic field strength is expressed in amperes.metre or milliamperesdmetre.
4.2 Residual output level
When the input signal to the hearing aid under test is turned off, the residual output level, due to, br example, ambient hum, noise and stray blelds In the test space, shall drop at least 10 dB and preferably 20 dB or more from the output level with the signal on.
4.3 MagnetIc field source
4.3.1 The test space shall be remote from any field-disturbing iron or other ferromagnetic material or other material In which eddy currents can be Induced that could give rise to a field disturbance.
4.3.2 The magnetic field source shall be provided with a calibration expressing the relationship between the magnetic field strength in amperesimetre at the test point and the input Current In amperes.
4.3.3 The magnetic field source shall be of such shape and dimensions that inside a sphere of diameter 10 cm of which the centre Is the test point, the deviation from nominal values in magnitude and direction is less than ±5% and ±10°, respectively.
NOTE – A quare loop with a Ext. length a greater than 0.5 m or a circular loop with a diameter d’ greater than 0.56 m wit meet these specification.