IEC 60645 1 Edition 3 0 2012 02 INTERNATIONAL STANDARD NORME INTERNATIONALE Electroacoustics – Audiometric equipment – Part 1 Equipment for pure tone audiometry Électroacoustique – Appareils audiométr[.]
General safety requirements
Audiometers shall conform to IEC safety requirements (see IEC 60601-1) except where otherwise specified in this standard.
Acoustic safety requirements
As audiometers are capable of producing sound pressure levels that could cause hearing damage, a non-auditory warning indication to the operator is required for all settings above
Environmental conditions
The specifications shall be met for combinations of temperature within the range of 15°C to
35°C, relative humidity within the range of 30 % to 90 % and ambient pressure within the range of 98 kPa to 104 kPa
The actual values of the environmental parameters at the time of calibration shall be stated
Note that reference equivalent threshold sound pressure levels can vary significantly with ambient pressures outside the specified range Therefore, recalibration at the nominal ambient pressure of the user's site is essential when the calibration site and user site have different ambient conditions This ensures accurate and reliable sound pressure level measurements.
Warm-up time
The audiometer must meet performance requirements after the specified warm-up time and any necessary adjustments per the manufacturer's instructions The manufacturer shall specify the minimum warm-up time, which must not exceed 10 minutes when the device is kept at the ambient temperature of the test environment.
Power supply variation
Interruption of power supply
If any interruption of the power supply occurs for up to 5 s, the audiometer shall revert to a condition that will neither endanger the subject’s hearing, nor yield invalid results.
Mains operation
The specifications must be met when the combined long-term deviation in mains supply voltage and frequency is at its most unfavorable, within the limits of ±10% for the mains supply voltage and ±5% for the mains frequency.
Battery operation
The manufacturer must define the battery voltage range within which the audiometer specifications are guaranteed An appropriate indicator should be included to confirm that the battery voltage remains within these specified limits The audiometer's performance must comply with the specifications at all battery voltages within the defined range.
Other power supplies
If an audiometer is powered by sources other than mains or battery, the manufacturer must specify the type of power supply, along with its characteristics and tolerances, to ensure the audiometer meets its performance specifications.
Electromagnetic compatibility
During EMC immunity testing conducted under IEC 60601-1-2 standards, any unwanted sound emitted from air conduction transducers must not exceed a hearing level of 80 dB Compliance with this requirement is demonstrated using the methods outlined in subclause 13.3.
Unwanted sound
General
Subjective tests are essential for detecting unwanted sound from audiometers when objective acoustical measurements are impractical These tests must involve at least two otologically normal subjects with hearing threshold levels not exceeding 10 dB across test frequencies from 250 Hz to 8 kHz The testing environment should comply with the specifications outlined in Table 4 of ISO 8253-1:2010 For extended high-frequency (EHF) audiometers, testing must include frequencies up to the highest available frequency to ensure accurate assessment.
NOTE For the frequency range above 8 kHz test rooms according to ISO 8253-1:2010 have shown in practice to provide sufficiently low ambient noise levels.
Unwanted sound from an earphone
Unwanted sound in an earphone can result from electrical signals generated within the audiometer when the tone switch is "OFF." Additionally, an unwanted tone, often referred to as breakthrough or cross talk, may occur in the non-test earphone when the test tone is "ON." Specific requirements for addressing these issues, along with an indirect electrical measurement method and a subjective performance verification method, are detailed in section 13.4.1.
An unwanted tone may also occur in the earphone due to the tone switch not being completely effective Requirements for the tone switch are described in 8.6.
Unwanted sound from a bone vibrator
The manufacturer must specify the test frequencies at which the bone vibrator may emit sound that could reach the test ear via air conduction through the unoccluded ear canal, potentially compromising the accuracy of bone conduction measurements Additionally, the manufacturer should indicate the possible degree of this impairment Compliance with this requirement can be demonstrated using the method outlined in section 13.4.2.
Unwanted sound radiated by an audiometer
Audiometers designed for use with the subject in the same room must ensure that any operational sounds from the audiometer controls, as well as radiation from the audiometer or associated computer systems, remain inaudible at all hearing level settings up to and including 50 dB Compliance with this requirement can be demonstrated using the method outlined in section 13.4.3.
The noise limitation on controls is designed to prevent any sound that could provide the patient with clues potentially affecting test results This restriction does not apply to mechanisms like output selection switches or detents on frequency switches that produce noise when the subject is not undergoing testing.
Testing of automatic-recording audiometers
Automatic-recording audiometers shall be provided with means to adequately control the signals for the purpose of measuring the characteristics of the audiometer.
Interface connections
No unintentional change of the audiometer’s calibration shall be possible via any interface
Pure tones
Frequency range and hearing level range
Fixed frequency audiometers must include test frequencies with minimum hearing level ranges specified in Table 2 for supra-aural earphones and bone vibrators For Type 1 audiometers equipped with circumaural or insert earphones, the maximum hearing levels can be up to 10 dB lower than the values listed for frequencies between 500 Hz and 8 kHz Additionally, frequencies up to 8 kHz may be utilized to enhance testing capabilities.
RETSPL values are given in the ISO 389 series
Table 2 – Minimum number of frequencies to be provided and the minimum range of values of hearing level for fixed frequency audiometers
Frequency in Hz Type 1 Type 2 Type 3 Type 4
Air Bone Air Bone Air Bone Air
8 000 100 – 90 – 80 – – a Maximum hearing level to be at least equal to the tabulated values Minimum hearing level to be –10 dB or lower
EHF test signals within the frequency range of 8,000 Hz to 16,000 Hz must follow the one-sixth-octave frequencies specified in ISO 266 The mandatory test signal frequencies include 8,000 Hz, 10,000 Hz, 12,500 Hz, and 16,000 Hz, with their corresponding hearing level ranges detailed in Table 3.
NOTE Some EHF instruments have the capability of going up to 20 kHz, but at present no standardized reference threshold data are available
Table 3 – Minimum range of values of hearing level for EHF audiometers
* 16 000 60 a Minimum hearing levels to be -10 dB or lower for all frequencies
6.1.1.3 Test signal level range for earphones
The minimum hearing level shall be -10 dB or lower
NOTE 1 Due to the large spread of hearing threshold levels in normal hearing subjects at the highest frequencies a minimum hearing level of -10 dB is not sufficient to reach threshold in many subjects Consequently, a minimum hearing level of less than -10 dB is recommended
NOTE 2 No requirement is given for the range of output for loudspeakers and bone vibrators
For sweep frequency audiometers, the range of frequencies and hearing levels shall be at least equal to those given in Table 2 for fixed frequency audiometers.
Frequency accuracy
For fixed frequency audiometers, the frequencies shall be equal to the stated values within the following tolerances:
For continuous sweep frequency audiometers, the frequency of the test tone shall agree with the value indicated on the audiogram within ± 5,5 %.
Total harmonic distortion
The maximum total harmonic distortion shall not exceed the values given in Table 4
Table 4 – Maximum permissible acoustic total harmonic distortion, for supra-aural, circumaural, insert earphonesand bone vibrators
Frequency range in Hz 125 to 200 250 to 400 500 to 8 000 250 to 400 500 to 800 1 000 to
Total harmonic distortion is maintained at 3% or 6%, depending on the conditions, or at the maximum output level of the audiometer, whichever is lower For circumaural and insert earphones, the hearing level should be set 10 dB lower than the levels specified in the standard table to ensure accurate audiometric measurements.
Rate of frequency change
Automatic recording audiometers with continuous sweep frequency must offer a frequency change rate of one octave per minute ± 25% For audiometers providing fixed frequencies, a minimum duration of 30 seconds should be maintained at each frequency to ensure accurate and reliable measurements.
Frequency modulation
If frequency modulated tones are provided they shall have the following characteristics: a) Carrier frequency
The carrier frequency shall be chosen from the audiometric test frequencies specified in
Table 2 with a tolerance of ± 3,5 % of the stated value b) Waveform of modulating signal
The waveform of the modulating signal shall be either sinusoidal or triangular with symmetrical rising and falling portions on a linear or on a logarithmic frequency scale
If the modulating waveform is sinusoidal, its total harmonic distortion shall not exceed
For a triangular waveform, the ramps must maintain a linear form with deviations not exceeding 5% of the amplitude Additionally, the durations of the rising and falling portions should not differ by more than 10% The repetition rate of the modulating signal is also a critical parameter to consider.
The repetition rate of the modulating signal shall be within the range of 4 Hz to 20 Hz with a tolerance of ± 15 % of its stated value d) Frequency deviation
The frequency deviation shall be in the range from ± 2,5 % to ± 12,5 % of the carrier frequency with a tolerance of ± 15 % of its stated value
The manufacturer shall state the characteristics and tolerances of the signals provided.
External signal source
Signals
Audiometers may involve the use of speech signals or other complex signals in addition to, or instead of pure tones IEC 60645-2 specifies equipment for speech audiometry and
ISO 8253-3 specifies techniques for speech audiometry This standard does not specify the parameters required for speech audiometry or for the use of complex signals.
Frequency response
For a constant voltage applied to the external input socket, the earphone's output sound pressure level, measured using the same ear simulator as the audiometer calibration, must not deviate by more than ±4 dB from the average sound pressure level of all test signals within the 250 Hz to 4 kHz frequency range This ensures consistent and accurate audio performance across the specified frequencies.
+ − dB and above 4 kHz the tolerance is − + 6 4 dB
For the bone vibrator output, the manufacturer shall specify the frequency response and tolerances in the frequency range from 250 Hz to 4 kHz.
Electrical sensitivity
The manufacturer must specify the electrical sensitivity of the external input by indicating the voltage of a given input signal required to achieve a specified output sound pressure level, with the signal indicator set at its reference position.
Reference level for external signal source
The external signal shall be capable of being monitored by a signal indicator (see 8.2) The reference level shall be stated when the signal indicator is at its reference position.
Operator to subject speech communication
A testing facility must enable clear speech communication from the operator to the test subject under normal conditions, ensuring the speech signal level is carefully controlled to avoid impacting the reliability of the test results.
Subject to operator speech communication
A facility shall allow speech communication from the test subject to the operator under normal test conditions.
Masking sound
General
For audiometers that offer masking sound, all masking sound measurements must be conducted using the same ear simulator or mechanical coupler employed for pure-tone measurements to ensure accuracy and consistency.
This standard specifies requirements exclusively for pure tones, indicating that the appropriate masking noise should be narrow-band noise Additionally, IEC 60645-2 defines masking noise for speech signals when integrated into a pure-tone audiometer, ensuring accurate auditory testing.
Narrow-band noise
Where narrow-band masking is required, the noise band shall be centred geometrically around the test frequencies The band limits for the masking noise are given in Table 5
Outside the specified band limits, the sound pressure spectrum density level of the noise must decrease by at least 12 dB per octave over a minimum of three octaves Additionally, the noise level should be at least 35 dB lower than the level at the center frequency Measurements are required within the frequency range from 31.5 Hz onward.
10 kHz for instruments limited to 8 kHz For EHF instruments measurements are required up to 20 kHz
Due to the limitations of transducers, ear simulators, and mechanical couplers, bandwidth measurements at 4 kHz and above may not accurately represent the masking noise spectrum Therefore, for center frequencies above 3.15 kHz, measurements should be conducted electrically across the transducer terminals to ensure precise results.
Table 5 presents the upper and lower cut-off frequencies for narrow-band masking noise, defined at a sound pressure spectrum density level of –3 dB relative to the level at the center frequency of the band This data is essential for accurately characterizing the frequency range of masking noise in acoustic studies Understanding these cut-off frequencies helps optimize sound masking applications by ensuring precise control over the spectral bandwidth.
Lower cut-off frequency in Hz Upper cut-off frequency in Hz
NOTE 1 The bands of noise correspond to one-third octaves as a minimum and one-half octaves as a maximum
At center frequencies of 400 Hz and above, these bands are wider than the critical bands for the same effective masking, requiring an overall sound pressure level approximately 3 dB higher than critical bands for effective masking (see ISO 389-4) Using wider bands helps minimize the perceived tonality of masking noise, enhancing auditory comfort.
NOTE 2 The minimum and maximum lower and upper cut-off frequencies, f l (min.), f l (max.), f u (min.) and f u (max.), are given by the following formulae (see IEC 61260): f l (min.) = f m /2 1/4 f l (max.) = f m /2 1/6 f u (min.) = f m × 2 1/6 f u (max.) = f m × 2 1/4 where f m is the centre frequency
NOTE 3 The given values are rounded to the first three significant digits.
Other masking sound
If other types of masking sound are provided the manufacturer shall specify the frequency spectrum and use
Type of transducers
The types of transducers used in pure-tone audiometry consist of different types of earphone
(supra-aural, circumaural and insert), bone vibrators and loudspeakers.
Headband
A headband shall be provided to hold supra-aural or circumaural earphones or bone vibrators with a nominal static force as specified in the ISO 389 series for that model of transducer
Alternatively, if a transducer requires a different static force to be used, this shall be stated by the manufacturer, and an appropriate headband shall be provided.
Loudspeaker
Sound-field audiometry environments can differ significantly from free-field conditions when using a loudspeaker ISO 8253-2 outlines the characteristics of free-field, diffuse-field, and quasi-free-field conditions, along with the procedures and usage conditions for sound-field audiometry Manufacturers are required to specify the test conditions applicable to the measurement of loudspeaker output performance.
Marking
The signal level control shall be identified by the designation “Hearing Level” (HL) or an equivalent national designation
The zero marking on the hearing level control corresponds to the output from the transducers aligned with the reference equivalent threshold values specified in the relevant sections of ISO 389.
Signal indicator
If a signal indicator is provided (refer to Table 1), the manufacturer must specify a reference reading that corresponds to the correct level of the external input signal for proper operation This signal indicator can also be used to monitor internally generated signals, ensuring accurate performance and reliability.
The manufacturer must specify the signal indicator's characteristics, including time weighting, dynamic range, and rectifier properties For indicators designed for speech signals, compliance with IEC 60645-2 standards is required to ensure accurate performance.
The indicator shall be connected at a point in the circuit before the hearing level control
Provision shall be made in the amplifier for adjustments of its gain to accommodate a range of
20 dB in the overall level of the signal presented
The manufacturer must specify the output level measured on the ear simulator with the hearing level control set to the stated value This measurement should be taken with the input activated by a specified signal at a stated level, which causes the monitor indicator to reach its reference indication.
Accuracy of sound pressure level and vibratory force level
When a single signal channel is connected to the earphone, the sound pressure level produced, minus the reference equivalent threshold level, must not deviate by more than ±3.7 dB from the specified value at any hearing level dial setting across the indicated frequencies within the range.
125 Hz to 4 kHz and by not more than ± 6,2 dB at frequencies up to and including 8 kHz At higher frequencies this difference shall be within ± 6,5 dB
Similarly the force level produced by the bone vibrator minus the reference equivalent threshold force level shall not differ by more than ± 5,5 dB in the frequency range 250 Hz to
4 kHz and by ± 7,0 dB at higher frequencies
When multiple channels for signal and/or noise are connected simultaneously to a single transducer, the output level of either signal or noise must not deviate by more than ±1.7 dB from the level obtained with a single channel at frequencies between 125 Hz and 4 kHz For frequencies from 5 kHz to 8 kHz, a tolerance of ±3.2 dB is allowed, while frequencies above 8 kHz and up to 16 kHz require a tolerance of ±3.5 dB These requirements apply to hearing levels up to 20 dB below the maximum output level.
Sweep frequency audiometers shall meet the requirements above at all appropriate one-third- octave frequencies; the output level shall vary smoothly between these frequencies.
Hearing level control
Manual audiometers
A hearing level control must feature a single scale and a unified reference zero point applicable to all frequencies The indicator readings for hearing level should be clearly marked at consistent intervals to ensure accuracy and ease of interpretation.
5 dB or less, with the 0 dB setting at each frequency corresponding to the reference equivalent threshold level.
Automatic-recording audiometers
All automatic-recording audiometers must offer a rate of change of 2.5 dB/s, with optional additional rates of 1.25 dB/s and/or 5 dB/s The tolerance for these rates should be maintained within ±25%.
The smallest increment of the hearing level control shall be stated by the manufacturer.
Accuracy of control
The difference (in decibels) between the measured difference and the indicated difference between two successive hearing level settings shall be less than or equal to the smaller of:
• three-tenths of the indicated difference in decibels or
• 1,5 dB for settings of -10 dB HL to 0 dB HL
• 1,4 dB for settings of 0 dB HL to 45 dB HL
• 1,2 dB for settings of 45 dB HL or greater
Masking level control
General
The masking level control shall have only one reference zero point that is common for all frequencies The masking level shall be adjustable in steps of 5 dB or less.
Masking level
For narrow-band noise, the masking level control must be calibrated in decibels of effective masking according to ISO 389-4 If the exact bandwidth of the masking noise is unknown but falls within the limits specified in Table 1 of ISO 389-4:1994, the mean values from columns 1 and 2 should be used For other types of sound, the masking level control should be calibrated in sound pressure level, measured with the earphone on the same ear simulator used for pure tone calibration Additionally, the manufacturer must specify both the overall sound pressure level and the sound pressure level in one-third-octave bands across the stated frequency range of the masking noise.
For EHF instruments, the masking level can be determined using Table 1 in ISO 389-4:1994, which provides data for one-third-octave bandwidths A practical approximation is to increase the reference equivalent threshold sound pressure levels by 5 dB to estimate the masking level accurately.
Accuracy of masking levels
The level of the masking sound produced by an earphone shall not differ from the indicated value by more than − + 4 6 dB
The measured difference in output between any two indications of masking level shall meet the requirements of 8.4.3 for pure tones
For measurement purposes, it is often more convenient to route a pure-tone test signal through the masking attenuator, especially given the time-varying nature of the narrow-band masking signal This approach simplifies the process and ensures accurate results when the masking attenuator facility is available.
Masking level range
The masking sound must be provided at levels adequate to effectively mask pure tones in the same ear, specifically at a hearing level of 60 dB at 250 Hz, 75 dB at 500 Hz, and 80 dB for frequencies ranging from 1 kHz and above.
4 kHz The level of the masking sound shall be adjustable over a range from 0 dB hearing level to these levels.
Tone switching
Tone switch for manual audiometers
Manual audiometers must include a tone switch that allows for the presentation or interruption of the test tone This switch and its related circuitry should be designed to ensure that the subject responds solely to the test tone, avoiding any influence from mechanical noise or signal switching transients.
NOTE An audiometer may be equipped with an automatic gating function for controlling the duration and/or repetition rate of a tone pulse.
On/off ratio for manual audiometers
When the switch is in the "OFF" position and the hearing level control is set at 60 dB or below, the output must be at least 10 dB below the reference equivalent threshold level For hearing level settings above 60 dB with the switch still in the "OFF" position, the output should not increase by more than 10 dB for every 10 dB rise in the hearing level setting.
Rise/fall times for manual audiometers
When the tone switch is moved to the "ON" position the rise time requirements shall be as follows (see Figure 1):
– AC rise time shall not exceed 200 ms;
– BC rise time shall be at least 20 ms;
– between B and C the sound pressure level shall rise in a progressive manner without discontinuities
When the tone switch is moved to the "OFF" position, the fall time requirements shall be as follows (see Figure 1):
– DH fall time shall not exceed 200 ms;
– EG fall time shall be at least 20 ms;
– between E and G the sound pressure level shall fall in a progressive manner without discontinuities
During both the rise and decay of the tone, the sound pressure level produced by the earphone must not exceed 1 dB above its steady-state level when in the "ON" position.
NOTE The measurement of AC and DH may require special consideration due to the uncertainty involved.
Automatic pulsed presentation
Where automatic pulsed presentation is made available, the pulse sequence generated shall meet the following requirements (see Figure 1):
– rise time: BC shall be at least 20 ms and shall not exceed 50 ms;
– fall time: EG shall be at least 20 ms and shall not exceed 50 ms;
– rise/fall rates: between B and C and between E and G the sound pressure level shall vary smoothly and without discontinuities;
– "ON" phase: CE shall be at least 150 ms;
– "ON"/"OFF" times: FJ and JK shall each have values of (225 ± 40) ms;
– “ON”/”OFF” ratio: between G and I the output shall remain at least 20 dB below the maximum reached in the “ON” phase CE
Instant of switch operation (ON)
Instant of switch operation (OFF)
Figure 1 – Rise/fall envelope of test tones
Subject’s response time for automated test procedures
The time available for a subject to respond to a test stimulus shall be specified by the manufacturer who shall state the algorithm for the test procedure.
Subject’s response system
The subject’s response system is a means by which the tester is made aware that the subject has responded to the signal
The response system in audiometers typically consists of a hand-held switch that activates a visual indicator on the device In automatic-recording audiometers, the subject's switch usually controls a specific function, such as adjusting the level of the test signal, ensuring accurate and efficient hearing assessments.
The switch must be designed for easy and reliable one-handed operation, ensuring it operates silently to prevent any errors in hearing threshold level measurements.
General
The requirements of Clause 9 apply where means are provided for the alternate or simultaneous presentation of a reference tone and a test tone of the same or different frequency
The operator must be able to present tones conveniently with appropriate durations and intervals Besides the main hearing level control that adjusts the sound pressure level of the test tone, an additional hearing level control is required to set the reference tone level, referred to as the reference tone level control The frequency accuracy, distortion, stability, and rise and fall characteristics of the reference tone must comply with the specifications outlined in other relevant sections of the standard.
Frequencies
As a minimum, the one-octave frequencies provided in the range 250 Hz to 4 kHz and additionally 6 kHz shall be available as reference tones for air conduction tests.
General
Conformance to this standard is confirmed only when the measurement result, including the expanded uncertainty from the testing laboratory, falls entirely within the specified tolerances If measurements are not applicable, conformance must be demonstrated through alternative methods such as visual inspection or review of supporting documentation.
Environmental conditions and power supply variation
Compliance with the specifications in section 5.3 must be verified using one sample of each different type of earphone supplied with the audiometer This verification involves measuring frequency, distortion, and sound pressure level at a 1 kHz indicated frequency, set at a hearing level of 100 dB or the maximum hearing level setting, whichever is lower Distortion measurements should follow the guidelines outlined in section 6.1.3.
Environmental tests according to 5.3 shall be performed at the following three combinations of temperature and relative humidity, the ambient pressure being within the range specified in
– and one additional combination from within the range specified in 5.3
For the specified temperature and relative humidity conditions, testing must also be conducted at pressures of 98 kPa (±1 kPa) and 104 kPa (±1 kPa), unless there is objective evidence demonstrating that ambient pressure does not significantly impact the results.
Conformity with the specifications in sections 5.4 and 5.5 must be demonstrated using a single sample of the earphone type supplied with the audiometer that delivers the highest sound pressure level Compliance is verified by measuring frequency, distortion, and sound pressure level at a 1 kHz indicated frequency, either at a hearing level of 100 dB or the maximum hearing level setting, whichever is lower Distortion measurements should follow the guidelines specified in section 6.1.3.
Electromagnetic compatibility
During EMC tests, the audiometer must be tested with all manufacturer-specified accessories and units Additionally, the audiometer should be evaluated in various positions relative to the radiating antenna to ensure comprehensive compliance.
The EMC testing environment must maintain ambient acoustic noise below 55 dB, measured with a one-third-octave filter at 1 kHz During testing, the audiometer's hearing level control should be set to its minimum, the frequency control to 1 kHz, and the tone switch turned "ON" for the right-hand air conduction transducer, if applicable EMC tests are conducted across a frequency range of 80 MHz to 2.5 GHz in 1% increments, with dwell times adjusted according to the specific instrument under test Testing orientations include angles of 0, 90, 180, and 270 degrees to ensure comprehensive assessment.
Testing at a limited number of frequencies does not negate the need to meet the requirements of 5.6.
Unwanted sound
Unwanted sound from an earphone
Unwanted sound, which can produce very low acoustic levels that are challenging to measure directly, is often determined indirectly through equivalent electrical measurements One effective method involves measuring the root mean square (r.m.s.) voltage generated across a suitable dummy load replacing the test earphone This measurement is conducted using a sound level meter with time-weighted F, in accordance with IEC 61672 standards.
A resistance matching the nominal impedance of the earphone is suitable for testing at each frequency When the hearing level control is set to 60 dB with the tone off, the electrical signal across frequencies from 125 Hz to 8 kHz must be at least 10 dB below the reference equivalent threshold level for the center frequency of the one-third-octave band Additionally, with the tone on, any unwanted signal in the non-test earphone or dummy load should be at least 70 dB below the test tone when the hearing level control is set to 70 dB or higher.
For subjective measurements of unwanted sound from the non-stimulus earphone, no test subject should detect any sound in the non-stimulus earphone within the frequency range of 250 Hz to 6 kHz at any masking or hearing level control setting up to 70 dB For frequencies outside this range but within 125 Hz to 8 kHz, no sound other than the test sound should be detected up to a setting of 50 dB The test must be performed with the tone switch in both the "ON" and "OFF" positions.
For higher settings, an external electrical attenuator must be inserted into the stimulus earphone connection Compliance tests at these higher settings should be conducted with the external attenuator adjusted to a value equal to the number of decibels above the audiometer hearing level settings minus 70 dB or 50 dB, respectively During testing, the opposite earphone must be disconnected, and the audiometer output terminals connected to an appropriate dummy load to ensure accurate measurements.
In the EHF range, no test subject should perceive any unwanted sound from the transducer during the presentation of the test tone, even when the hearing level control is set to its maximum.
Many test subjects with minimal hearing ability at 14 kHz and 16 kHz demonstrate significantly better hearing at lower frequencies This important observation is not addressed in section 5.7 of the standard.
Unwanted sound from a bone vibrator
The influence of sound radiation from the bone vibrator on audiometric test results is assessed by first determining the bone conduction threshold at 2 kHz and above for each frequency provided by the audiometer, following ISO 8253-1:2010 standards, with the test ear occluded using an earplug that offers a mean attenuation of at least 20 dB as per ISO 4869-1 This step is then repeated without the earplug, and finally, the mean hearing thresholds from both conditions are calculated at each frequency to ensure accurate assessment.
The influence is considered negligible when the mean hearing threshold levels of 16 ears, meeting the criteria of section 5.7.1, show that the difference between each pair of mean values does not exceed 3 dB.
NOTE The maximum permissible total harmonic distortion given in Table 4 may lead to false bone conduction thresholds due to the perception of harmonics of lower test frequencies.
Unwanted sound radiated by an audiometer
The test for the requirements in 5.7.4 shall be made on at least two test subjects meeting the requirements of 5.7.1, wearing a pair of disconnected earphones and located at a distance of
The audiometer's electrical output must be measured at a distance of 1 meter and absorbed by a resistive load matching the earphone's impedance at 1 kHz When a bone conduction facility is available, the test should be repeated with the ears unoccluded to ensure accurate results.
Total harmonic distortion of test signals
Conformity with the specification in 6.1.3 shall be determined at the hearing levels listed in
According to the procedure specified in IEC 60268-3, distortion measurements should be conducted at Table 2 levels or the maximum hearing level setting on the audiometer, whichever is lower, excluding harmonics above 16 kHz For air conduction, distortion must be measured acoustically using an ear simulator designed for specifying equivalent reference threshold levels, while for bone conduction, distortion should be measured on a mechanical coupler.
Manufacturers must specify the frequencies and hearing levels at which the non-linearity of bone vibrators may affect the accuracy of bone conduction measurements, as setting a maximum permissible harmonic distortion alone cannot guarantee precise results for all types of hearing loss.
NOTE Due to the limitations of ear simulators and mechanical couplers, measurements of harmonics may not accurately describe the non-linear properties of the system.
Signal accuracy
Accuracy of sound pressure level and vibratory force level
Each individual earphone must demonstrate conformity with the specifications in section 8.3 by measuring the output at a hearing level setting of 70 dB or the maximum level, whichever is lower, across all available frequencies using a specified ear simulator For bone vibrators, the hearing level setting should be 30 dB or the maximum, whichever is lower, with measurements taken on a mechanical coupler as outlined in IEC 60318-6.
Accuracy of hearing level control
The accuracy of hearing level control must be tested at a minimum frequency of 1 kHz, with an additional test at 8 kHz if an EHF option is available Whenever feasible, acoustic measurements should be used to verify conformity with the requirements in section 8.4.3 If electrical measurements are conducted, they should be taken at the input to the transducer connected to an ear simulator, or alternatively, the transducer can be replaced by a dummy electrical load that simulates the transducer at the test frequency.
Masking sound
Narrow-band noise
Compliance with section 6.4.2 must be verified up to 3.15 kHz by acoustically measuring the masking noise spectrum using the same ear simulator employed for pure tone measurements For frequencies above 3.15 kHz, the measurement should be conducted electrically across the transducer terminals while positioned on the same ear simulator.
Masking level
Conformity with the specification in 8.5.3 shall be demonstrated using a sound level meter that conforms to the class 1 requirements of IEC 61672-1, by measuring the S time-weighted,
Z frequency-weighted sound level at a hearing level setting of 70 dB at all available frequencies and with the same ear simulator as used for the measurement of pure tones.
Headbands
General
The requirements outlined in section 7.2 are considered fulfilled if the headband static force meets the specifications of the ISO 389 series or the manufacturer's specifications for the specific transducer model, with the stated tolerances adjusted to include the maximum allowable measurement uncertainties as detailed in Table 8.
Supra-aural and circumaural earphone headband
To demonstrate conformity, the earphones must be positioned with a horizontal separation of 145 mm, while simultaneously adjusting the headband height to achieve a vertical distance of 129 mm This vertical measurement is taken from the center top of the headband to a line connecting the centers of the earphones The allowable tolerance for these dimensions is ± 5 mm.
Bone vibrator headband
To demonstrate conformity, the spacing between the bone vibrator and the opposite end of the headband must comply with the requirements specified in section 13.8.2 However, for forehead placement, the spacing should be set at 190 mm with a tolerance of ± 5 mm.
14 Maximum permitted expanded uncertainty of measurements U max
The table outlines the maximum permitted expanded uncertainty for a coverage factor of k = 2, relevant to the measurements conducted under this standard It provides a specific set of U max values applicable to both basic type approval measurements and periodic verification, ensuring consistent accuracy and compliance.
The expanded uncertainties of measurement listed in Table 8 represent the maximum allowable limits for demonstrating compliance with this standard If a test laboratory or maintenance service obtains an expanded uncertainty exceeding these limits, the measurement cannot be used to verify conformance to the standard’s requirements.
Table 8 – Values of U max for basic measurements
Measured quantity Relevant subclause number Basic
Sound pressure level 125 Hz to 4 000 Hz 8.3, 9.3.4 0,7 dB
Sound pressure level 5 000 Hz to 8 000 Hz 8.3, 9.3.4 1,2 dB
Sound pressure level 9 000 Hz to 16 000 Hz 8.3, 9.3.4 1,5 dB
Narrow-band masking noise cut-off frequencies 6.4.2 1 %
Masking level 125 Hz to 4 000 Hz 8.5.3 1,0 dB
Force level 250 Hz to 4 000 Hz 8.3 1,5 dB
Force level greater than 4 000 Hz 8.3 2,0 dB
Rate of change in level (%) 8.4.2 5 %
Linearity of hearing level control -10 to 0 dB
Linearity of hearing level control 5 dB to
Linearity of hearing level control above
Rise and fall time 8.6.3, 8.6.4 5 ms
Marking
The audiometer shall be marked with the name of the manufacturer, the model, the type (see
Table 1) and the serial number An individual instrument identification shall also be marked on the test signal transducers
The left and right earphones shall be readily identifiable If the earphones are colour coded the left earphone shall be coded blue and the right earphone red.
Instruction manual
An instruction manual must accompany the audiometer, detailing the instrument type as per the relevant standard and describing its features along with comprehensive operating instructions It should specify permissible power supply variations and environmental conditions to ensure compliance with performance requirements The manual must include guidelines for proper installation to minimize unwanted sound radiation Identification of transducers and their reference equivalent threshold levels should be provided, including the origin of reference levels if different from ISO, the ear simulator used for calibration, and the static force applied Additionally, it should clarify whether bone vibrator calibration pertains to mastoid or forehead placement, and describe the frequency response characteristics and masking effects of the masking sound supplied.
The manufacturer must specify the actual bandwidth of the narrow-band masking noise, the warm-up time, and the sensitivities and nominal impedances of all input facilities Additionally, the available voltage and nominal impedance of all output facilities, along with the pin assignment of all external plug connections, should be clearly stated For automatic-recording audiometers, the mode of operation and the rate of change of sound pressure level must be provided In the case of audiometers with continuously variable frequency, the rate of frequency change should be indicated Furthermore, when frequency-modulated signals are used, the manufacturer is required to detail the relevant characteristics and tolerances.
– the frequency of the modulating signal;
– the modulation waveform, i.e sine wave or triangular;
– the modulation range expressed as a percentage of the test frequency; j) sound attenuation characteristics of the earphones as measured in accordance with
ISO 4869-1 outlines key specifications for audiometers, including maximum hearing level settings at each test frequency and limitations due to harmonic distortion It addresses the effects of airborne sound radiation from bone vibrators and methods to ensure accurate test results The standard provides information on the time window for subject responses in automated test procedures, as specified in section 8.6.5 For battery-operated devices, details on battery type, checking methods, replacement procedures, and expected battery life are included Maintenance and calibration procedures, along with schedules, are guided by ISO 8253-1:2010 Additionally, an EMC warning is required to inform users about potential impacts of radiated electromagnetic fields, especially from high-powered medical devices, on audiometer performance.
IEC 61260, Electroacoustics – Octave-band and fractional-octave-band filters
ISO/IEC Guide 98-3, Uncertainty of measurement – Part 3:Guide to the expression of uncertainty in measurement (GUM:1995)
ISO 389-9, Acoustics – Reference zero for the calibration of audiometric equipment – Part 9:
Preferred test conditions for the determination of reference hearing threshold levels
4 Exigences pour des types spécifiques d'audiomètres à fréquences fixes 44
5.2 Exigences concernant la sécurité acoustique 46
5.4 Durée de mise en température 46
5.7.2 Sons indésirables émis par un écouteur 47
5.7.3 Sons indésirables émis par un ossivibrateur 47
5.7.4 Sons indésirables émis par un audiomètre 47
5.8 Essais des audiomètres automatiques enregistreurs 48
6.1.1 Domaine de fréquences et de niveaux d'audition 48
6.1.4 Vitesse de variation de la fréquence 50
6.3.4 Niveau de référence pour la source externe du signal 51
6.3.5 Communication verbale de l'opérateur vers le sujet 51
6.3.6 Communication verbale du sujet vers l'opérateur 51
8 Commande de niveau du signal 54
8.3 Exactitude des niveaux de pression acoustique et de force vibratoire 55
8.5 Commande de niveau du bruit de masquage 56
8.5.2 Niveau du bruit de masquage 56
8.5.3 Exactitude des niveaux de bruit de masquage 56
8.5.4 Domaine de variation de niveau du bruit de masquage 56
8.6.1 Interrupteur de son pour les audiomètres manuels 56
8.6.2 Rapport émission/coupure pour les audiomètres manuels 57
8.6.3 Durées d'établissement et d'extinction du son pour les audiomètres manuels 57 8.6.4 Présentation automatique de sons pulsés 57
8.6.5 Temps de réponse du sujet pour les procédures d'essais automatisées 58 8.6.6 Dispositif de réponse du sujet 58
9.3 Commande de niveau du son de référence 59
11 Sortie électrique des signaux d'essais 60
13 Exigences d’essai permettant de montrer la conformité 61
13.2 Conditions ambiantes et variations de la tension d’alimentation 62
13.4.1 Sons indésirables émis par un écouteur 62
13.4.2 Sons indésirables émis par un ossivibrateur 63
13.4.3 Sons indésirables émis par un audiomètre 64
13.5 Distorsion harmonique totale des signaux d'essai 64
13.6.1 Exactitude du niveau de pression acoustique et de force vibratoire 64
13.6.2 Exactitude de la commande du niveau d’audition 64
13.7.2 Niveau du bruit de masquage 65
13.8.2 Serre-tête pour écouteur supra-aural et circumaural 65
14 Valeurs maximales autorisées pour l'incertitude élargie des mesures U max 65
Figure 1 – Enveloppes des signaux d’établissement/d’extinction des sons d’essai 58
Tableau 1 – Caractéristiques minimales pour les audiomètres à fréquences fixes 45
Tableau 2 – Nombre minimal de fréquences à fournir et domaine minimal de valeurs de niveaux d’audition pour les audiomètres à fréquences fixes 48
Tableau 3 – Gamme minimale de valeurs de niveau d’audition pour audiomètres EHF 49
Tableau 4 – Valeurs maximales admissibles de la distorsion acoustique harmonique totale pour les écouteurs supra-auraux, circumauraux ou à emboutset pour les ossivibrateurs 50
Table 5 presents narrowband masking noise cutoff frequencies, detailing the lower and upper limits for an acoustic pressure spectral density level of –3 dB relative to the level at the median frequency of the band This data is essential for understanding frequency-specific masking effects in acoustic analysis.
Tableau 6 – Normes de référence pour obtenir le zéro audiométrique 60
Tableau 7 – Symboles pour la représentation graphique des niveaux de seuil d'audition 61
Tableau 8 – Valeurs de U max pour les mesures fondamentales 66
ÉLECTROACOUSTIQUE – APPAREILS AUDIOMÉTRIQUES – Partie 1: Appareils pour l’audiométrie tonale
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La Norme Internationale CEI 60645-1 a été établie par le comité d'études 29 de la CEI: Électroacoustique
Cette troisième édition annule et remplace la deuxième édition parue en 2001, et la
CEI 60645-4 parue en 1994 Elle constitue une révision éditoriale
Le texte de cette norme est issu des documents suivants:
Le rapport de vote indiqué dans le tableau ci-dessus donne toute information sur le vote ayant abouti à l'approbation de cette norme
Cette publication a été rédigée selon les Directives ISO/CEI, Partie 2
Une liste de toutes les parties de la série CEI 60645, présentées sous le titre général
Electroacoustique, peut être consultée sur le site web de la CEI
Future standards in this series will now carry the new general title mentioned above Existing standards within this series will be updated with this new title in the upcoming edition.
The committee has decided that the content of this publication will remain unchanged until the stability date specified on the IEC website at "http://webstore.iec.ch" within the data related to the searched publication On that date, the publication will be reviewed accordingly.
• remplacée par une édition révisée, ou
Advancements in hearing measurement technologies for diagnostic, preservation, and rehabilitation purposes have led to a wide variety of audiometers available on the market Audiometers can be viewed in terms of functional units that can be individually specified, allowing for clear definition of their properties This approach also facilitates the specification of other audiometric devices that incorporate these units The IEC 60645 series consists of multiple parts, with IEC 60645-1 being the first, addressing the requirements for pure-tone audiometers.
La prộsente norme dộcrit des appareils qui sont conỗus pour mesurer l’audition dans un domaine de fréquence compris entre 125 Hz et 16 000 Hz
En raison de la publication ultérieure des autres parties de la CEI 60645, il n'est à présent pas fait référence, dans la partie 1, à l'utilisation de bruit à large bande pour le masquage
Les exigences concernant les bruits de masquage à large bande se rapportent à leur utilisation avec les signaux de parole tels qu’ils sont décrits dans la CEI 60645-2
The testing requirements to demonstrate compliance are now specified independently Compliance with the specifications of this Standard is verified only when the measurement result, increased by the actual expanded uncertainty of the testing laboratory's measurement, fully falls within the tolerances specified in this Standard The tolerances that the audiometer manufacturer must meet are essentially the same as those given in the first edition of the Standard.
CEI 60645-1, alors que les tolérances qui sont applicables pour l’essai de l’audiomètre sont augmentées de la valeur U max par rapport à celles qui sont données dans la précédente édition
La série CEI 60645 est constituée des parties suivantes:
CEI 60645-1, Électroacoustique – Appareils audiométriques – Partie 1: Appareils pour l’audiométrie tonale
CEI 60645-2, Audiomètres – Partie 2: Appareils pour l’audiométrie vocale
CEI 60645-3, Électroacoustique – Equipements audiométriques – Partie 3: Signaux d’essai de courte durée
CEI 60645-4, Audiomètres – Partie 4: Equipement pour l'audiométrie étendue au domaine des fréquences élevées
CEI 60645-5, Électroacoustique – Appareillage audiométrique – Partie 5: Instruments pour la mesure de l’impédance ou de l’admittance aurale (impédancemètres ou admittancemètres)
CEI 60645-6, Électroacoustique – Equipements audiométriques – Partie 6: Instruments pour la mesure des émissions otoacoustiques
CEI 60645-7, Électroacoustique – Equipements audiométriques – Partie 7: Instruments pour la mesure des réponses du tronc cérébral à une stimulation auditive ÉLECTROACOUSTIQUE – APPAREILS AUDIOMÉTRIQUES – Partie 1: Appareils pour l’audiométrie tonale