BS EN 60318-4:2010 pdf download
BS EN 60318-4:2010 pdf download.Electroacoustics一Simulators of human head and ear Part 4: Occluded-ear simulator for the measurement of earphones coupled to the ear by means of ear inserts.
3.10
effective volume
equivalent volume of air of the acoustic compliance of the ear simulator formed by the cavity and the microphone at a frequency of 500 Hz
unit: mm3
4 Construction
4.1 General
The occluded-ear simulator shall be constructed of hard, dimensionally stable, non-porous and non-magnetic material. The general construction of the occluded-ear simulator and mounting of the microphone shall aim at minimizing the response of the microphone to vibration (for example from an earphone) or to extraneous sound outside the cavity.
NOTE 1 The eicternal diameter of the occluded-ear simulator should be kepi as small as possible in order 10 minimize diffracl,onal errors wfi.cti might affect the measurements when th occluded.-ear simulator has to be placed in a tree sound field.
NOTE 2 In order to avoid a possible sound attenuation caused by the dust protector (see Figure Al). an earphone Calibration should be performed above 10 kHZ at least every two years with the occluded-ear simulator equipped with and wrthout is dust protector in place Th, two results should not differ by more than 0,2 dO at frequencies up to 16 ktlz. if thu Is not the case at join. frequencies, earphone measurements at those frequencies shotAd generally be performed mttioul the dust protector.
The construction of the occluded-ear simulator shall permit the location of a transducer at the reference plane for calibrating the simulator.
Where tolerances are specified in this part of lEG 60318, these shall be reduced by an amount equal to the actual expanded measurement uncertainly of the test laboratory before deciding if a device conforms to the stated requirement
4.2 Principal cavity dimensions
The diameter Of the principal cavity shall be (7,50 ± 0,04) mm.
The length of the principal cavity shall be such as to produce a half-wavelength resonance of the sound pressure at (13.5 ± 1,5) kHz.
4.3 Calibrated pressure-type microphone
A calibrated microphone is located at the base of principal cavity of the occluded-ear simulator. The acoustic impedance of the microphone diaphragm shall be high, so that the equivalent volume is less than 20 mm3 over the specified range of frequencies. The microphone shall conform to the requirements of IEC 61094-4 for a type WS2P microphone. The microphone shall be coupled to the principal cavity with a seal that prevents acoustic leaks.
In the frequency range 20 Hz to 10 kHz, the overall sound pressure sensitivity level of the microphone and associated measuring system shall be known with an uncertainty not exceeding 0.3 dB for a level of confidence of 95 %. For measurements above 10 kHz. the overall pressure sensitivity level of the microphone and associated measuring system over the specified frequency range shall be known with an uncertainty not exceeding 0,5 dB for a level of confidence of 95 %.
The make and model of the microphone shall be specified by the manufacturer of the occluded-ear simulator.
The calibration should be performed for the atmospheric reference conditions given In 5.1 wIth
the rolowing tolerances:
Ambient pressure: ± 3 kPa
Temperature: ± 3 C
Relative humidity: ± 20 %
If It Is not possible to perform the calibration at reference conditions, the calibration shall be
referred to the atmospheric reference conditions given in 5.1, see 181, 191.
6 Coupling of earphones and hearing aids to the occluded.ear simulator
6.1 AudIometers wIth lns.rt earphones
Insert earphones with standardized reference equivalent threshold Sound pressure levels shall be connected to the occluded-ear simulator as specified in the relevant ISO standards. For other earphones, the manufacturer of the audiometer shall describe the method of connection,
NOTE Retetence hearing miegnoid eound pressure levels 01 insert earpilones to, audiometers and it. connection to the Occluded-ear simulator are standardized In ISO 389-2 III. ISO 389-5121 and ISO 3894(3)
6.2 In-the.ear hearing aids (custom made)
The hearing aid shall be connected directly to the cavity of the occluded-ear simulator as indicated in Figure 1. The connection between the hearing aid and the occluded-ear simulator shall be made airtight by using a suitable seal. In doing so. care shall be taken not to introduce additional volume to the cavity which can affect the measured performance of the hearing aid.
In the same way, a hearing aid equipped with a separate ear insert can be measured.
