This standard covers the design of instruments, mainly for measuring the modulus of acoustic impedance/admittance of the external ear using a 226 Hz probe tone. This standard also specifies the characteristics specified by the manufacturer, gives the performance indicators of four types and the facilities to be provided for three of them. It also specifies the methods used for type approval tests other than routine calibration. GB/T 15953-1995 Instruments for measuring acoustic impedance/admittance of the ear GB/T15953-1995 Standard download decompression password: www.bzxz.net
This standard covers the design of instruments, mainly for measuring the modulus of acoustic impedance/admittance of the external ear using a 226 Hz probe tone. This standard also specifies the characteristics specified by the manufacturer, gives the performance indicators of four types and the facilities to be provided for three of them. It also specifies the methods used for type approval tests other than routine calibration.

GB/T15953--1995
This standard is formulated based on the International Electrotechnical Commission standard 1EC1027 Instruments for the measurement of otoacoustic impedance/admittance (1991-03 Edition). Since this international standard is technically mature, widely promoted internationally, and meets the product specifications used in various parts of my country, it is adopted as an equivalent to adapt to the needs of international trade, technical and economic exchanges and the adoption of international standards as soon as possible. Appendix A of this standard is a prompt appendix.
This standard is proposed by the China Institute of Metrology. This standard is under the jurisdiction of the China Institute of Metrology. The drafting unit of this standard: China Institute of Metrology. The main drafters of this standard are Zhang Jucai and Shi Zhengping. GB/T15953—1995
IEC Foreword
I) Formal resolutions or agreements on IEC technical documents prepared by technical committees attended by all national committees with special interest in the project express, as far as possible, international consensus on the subject matter involved. 2) They are used internationally in the form of international recommendations and are adopted by national committees in this sense. 3) In order to promote international unification, IEC hopes that all national committees will adopt the texts of IEC recommendations as national regulations as far as possible, where national conditions permit. Any deviation between IEC recommendations and corresponding national regulations should be clearly stated in the latter as far as possible. Foreword
This standard is provided by IEC Technical Committee 29\Electroacoustics\. The text of this standard is based on the following documents:
Six-month method
29(CO)156
Voting report
29(CO)143
One-month method
29(CO)144
Full information on the voting for the approval of this standard can be found in the voting report shown in the table above. The following announcements are referenced in this standard:
Voting report
29(CO)155
126(1973); IEC reference coupling cavity for hearing aids coupling headphones to the human ear by insert earphones. 6011(1977): Medical electronic equipment, part 1: General requirements. 645-1(1992): Audiometer + Part 1: Pure tone audiometer. 711(1981): Insert earphones are used to couple the earphones to the human ear. Occluded ear simulator for measuring headphones coupled to the human ear. Other bulletins cited,
IS0 Standard 389 (1985): Acoustics - Standard reference for calibration of pure air conduction audiometers Level 1 Supplement 01:1983
Supplement 02:1986
GB/T15953-1995
Developments in the field of diagnostic audiometry have led to the design of a range of instruments for evaluating the acoustic impedance/admittance of the human ear. Such instruments use acoustic probe signals with different rate and time characteristics. Their practical use exploits a wide range of variations in acoustic impedance/admittance. Such variations can be induced by changing the air pressure in the external auditory canal or by stimulating the middle ear muscle reflex. 1 Scope
National Standard of the People's Republic of China
Instruments for measuring acoustic impedance/admittance of the ear
Instruments This standard covers the design of instruments, mainly measuring the modulus of acoustic impedance/admittance of the external ear using a 226Hz probe tone. This standard also specifies the characteristics specified by the manufacturer, gives the performance indicators of four types and the facilities to be provided for three of them. It also specifies the methods used for type approval tests other than routine calibration. This standard is intended to ensure that measurements with comparable test conditions using different instruments that comply with this standard can be included. This standard does not intend to restrict the development and utilization of new characteristics, nor does it hinder innovative methods. 2 Reference standards
The provisions contained in the following standards constitute the provisions of this standard through their use in this standard. At the time of publication of this standard, the following versions are: valid. All standards are subject to revision, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB4854-84 Standard zero-level GB for calibration of pure tone audiometers 7311—87 Audiometer
SJ/Z 9144—87 Test disc IEC reference coupler for hearing aid earplugs Test base Occluded ear canal cavity simulator for earplugs SJ/Z 9150—87
IEC601-1(1977)
Medical electronic equipment Part 1, General requirements 3 Definitions
This standard adopts the following definitions:
Note: The units of this standard follow the International System of Units, but other units are often used in audiological test results. To convert them into the International System of Units, Appendix A is specially compiled.
3.1 Aural impedance/admittance aural impedance/admittance Except for special derived standards, this standard adopts aural impedance/admittance as the general term for ear acoustic impedance/admittance. 3.2 Acoustic impedance Ecoustie fmpedance The complex ratio of the average sound pressure on the entire surface to the volume velocity through the surface on a given surface. Symbol is Z., unit is Pascal seconds per cubic meter (Pa, s/m\). The modulus is usually measured. 3.3 Acousticresistance
The real component of the complex acoustic impedance. Symbol is R, unit is Pascal seconds per cubic meter (Pa·s/m\). 3.4 Acousticreactance
The real component of the complex acoustic impedance is symbolized by X, unit is Pascal seconds per cubic meter (Pa·s/m\). 3.5 Acoustic admittance Acoustic admittance The reciprocal of the acoustic impedance of a given surface. Symbol is Y, unit is cubic meter per Pascal second (m\/Pa·s), therefore the admittance on a given surface is the complex ratio of the volume velocity through the surface to the average sound pressure on the surface, and the quantity measured is usually the modulus. National Technical Standards
3.6 Acoustic conductance GB/T 15953-1995
The real component of complex acoustic admittance. Symbol is G, and the unit is m3/Pa-second (m/Pa·s). 3.7 Acousticusceptance
The imaginary component of complex acoustic admittance. Symbol is B, and the unit is m3/Pa·s (m\/Pa·s). 3.8 Acoustic inertance
The ratio of the rate of change of the volume velocity obtained by the excitation sound. Symbol is M. The unit is Pa-second-squared per cubic meter (Pa,/m\). 3.9 Acoustic compliance The ratio of volume displacement to acoustic compliancy. Symbol is (, unit is cubic meter per Pa (m\/Pa). 3.10 Equivalent volume equivalenlvolume The volume of a hard-walled circular air cavity that provides equivalent acoustic impedance/admittance. It can be expressed by the formula: V.=-YPC=.2.C.
Where: .
Equivalent volume.rra\;
The ratio of the specific heat of air at constant pressure to the specific heat of air at constant volume, approximately 1.40Air pressure, Pa
The temperature at the time of measurement and the air density at atmospheric pressure, kg/m; The temperature at the time of measurement and the speed of sound at atmospheric pressure, m/31C. Acoustic compliance, m'/Pa.
1In practice, the impedance/admittance of the probe pure audio room at 226Hz has been used as the equivalent volume of air. 2For the pure frequency of the probe at 226Hz, as long as the physical volume does not exceed 5 cm., the equivalent volume of air is equal to its physical volume. 3.11 Relative pressure in the external auditory canal relative pressure in the external auditory canal is the difference between the pressure in the external auditory canal and the atmospheric pressure, in units of 10Pa (daPa). Note: In audiological measurements, the air pressure is usually expressed in terms of the height of a supported water column, in units of mmH,. The corresponding international unit is 10 Pa+. For comparison with inertial measurement, it is recommended to use 10 Pa (daPa) (1 daPa = 1.02 mmH,0). 3.12 Probe Probe
is a device that is inserted into the external auditory canal to connect the instrument to the human ear. 3.13 Probe cuff
is a device used to seal the probe from the external auditory canal. 3.14 Probe signal prabe signal
is an acoustic signal sent by the probe to the external auditory canal, used to measure acoustic impedance/admittance. 3.15probeearprobeear
ear with probe inserted,
3. 16 measurement planemeasurement planeThe plane in which the front surface of the probe is perpendicular to the volume velocity measurement. 3.17tympanometry
The measurement of the change in middle ear acoustic impedance/admittance with air pressure in the external auditory canal. Note: The measured acoustic impedance/admittance value will be related to the rate and direction of change of air pressure and also to the time required to maintain a constant pressure in the external auditory canal.
3.17.1 Measurement plane tympanometrymeasurement plane tympanometryThe measurement of the change in ear impedance/admittance in the measurement plane, including the combined impedance/admittance of the middle ear and part of the external auditory canal. 3.17.2 Tympanometry Measurement of the difference between the acoustic impedance/admittance of the ear in the external auditory canal for a given probe fit at a specified reference pressure and at a test pressure. Note: The reference pressure band is the difference between 20 daPa and the indicated pressure. It may also be defined as 200 daPa relative to ambient pressure. It gives an indication of maximum admittance or minimum impedance. 3.18 Tympanogram A graphic representation of the change in the impedance/admittance of the middle ear in the external auditory canal with atmospheric pressure. 3.19 Middle-ear muscle reflex Change in the tension of the middle ear muscles in response to a stimulus. This change can be accounted for by the change in acoustic impedance/admittance in the external auditory canal. 3.19.1 Acoustic reflex A reflex of the middle ear muscles induced by acoustic stimulation.
3.19.2 Non-acoustic reflex A reflex of the middle ear muscles not induced by acoustic stimulation. 3.20 Acoustic reflex activating stimulus A stimulus used to induce an acoustic reflex.
3.21 Stimulusear
The ear that provides the reflex activating stimulus to induce the middle ear reflex. 3.22 Ipsilateral reflex A reflex of the middle ear muscles induced in the stimulated ear. 3.23 Contralateral reflex A reflex of the middle ear muscles induced in the ear opposite to the stimulated ear. 4 Characteristics to be specified by the manufacturer
4.1 Impedance/admittance measurement system
4.1.1 Effects of ambient temperature and atmospheric pressure The effects of ambient temperature and atmospheric pressure are critical factors in impedance measurements. The manufacturer shall provide the user with data that will allow correct calibration when using a suitable test chamber as specified in Section 7. 4.1.2 Probe dimensions
The manufacturer shall provide specified information on the dimensions of the probe and any associated tubes between the probe and the instrument. Note: Probes with standard characteristics and dimensions are desirable, but recent developments may not specify any dimensional requirements. 4.1.3 Maintenance information
The manufacturer shall provide information on cleaning, maintenance and replacement of the probe, any associated tubes and probe clips. The manufacturer shall also give advice on the intervals for repeating these procedures.
4.1.4 Probe signal characteristics
4.1.4.1 Frequency
The probe signal frequency for Type 1 to Type 3 instruments shall be 226 Hz. The manufacturer may also provide any additional probes that meet the tolerances of 5.2.2.
Note: Under standard atmospheric conditions (atmospheric pressure of 110 kPa and temperature of 20°C), the acoustic admittance of a 1 cm variable air cavity at a frequency of 226 Hz is 10-m/1n. 4.1.4.2 Signal level
The manufacturer shall specify the tolerances of the probe signal sound pressure level given in 5.2.3 and its variation with load volume and its measurement conditions. 4.1.4.3 Unstable probe signal
For probe signals that are not stable, the manufacturer shall specify the time characteristics and spectral characteristics of the probe signal and shall also specify the procedures and tolerances for measuring these characteristics.
4.1.5 Acoustic impedance/admittance indicator
Manufacturing process type and units used, differential, and its dependence on the annual pressure 4.1.6 Electrical output
GB/T15953--1995
When there is an electrical output, the manufacturer shall state the sensitivity expressed in voltage/indication: any DC bias, type of circuit (single-ended or differential), type of plug and socket used, and the minimum electrical load impedance for the specified sensitivity. If relevant to 4.1.7, the time characteristics of the electrical output shall also be specified.
4.1.7 Time characteristics
For instruments providing measurements of the time characteristics of acoustic reflections, the initial latency, rise time, terminal latency, fall time and overshoot-undershoot characteristics shall be relevant to obtaining accurate measurements. For all types of impedance/admittance instruments, the manufacturer shall specify these characteristics and provide tolerances for each characteristic.
4.2 Pneumatic Systems
4.2.1 Pressure Control Systems
The range of pressure changes relative to sub-atmospheric pressure must be specified and, when there is a dynamic change, the rate of change shall also be specified. 4.2.2 Pressure Indicators
The pressure in the external auditory canal shall be expressed by an analog or digital display. The accuracy of the display and the limits relative to atmospheric pressure and sea level shall also be specified.
4.2.3 Electrical Outputs
When electrical outputs are provided, the sensitivity shall be stated in units of voltage/air pressure (V/daPa). The specification shall also include any DC bias, the type of auxiliary output circuit (single-ended or balanced), and the type of plug and socket used. The minimum load disturbance for the specified sensitivity shall also be stated. The time characteristics of the electrical output system shall be specified in terms of the rise time of the system response to a step-by-step pressure change. 4.3 Acoustic reflex activation (stimulation) system
The manufacturer shall specify the type of stimulus signal used. For acoustic stimulation, the manufacturer shall specify the pure tone frequency, tolerance, maximum harmonic distortion, type of noise used and its characteristics and tolerance. For non-acoustic stimulation, the manufacturer shall specify the stimulus type and describe its characteristics and tolerance. 4.3.1 Stimulus level control
The manufacturer shall specify the accuracy, range, interval and maximum output level of the acoustic signal stimulus level control used, as well as other relevant characteristics. 4.3.2 Stimulus presentation control
For acoustic stimulation, the manufacturer shall specify the "on" and "off" ratios, rise and fall times, and the residual A-weighted sound pressure level in the "off" condition. If pulse signals are used, the manufacturer shall specify the time characteristics and tolerances. For non-acoustic stimulation, the manufacturer shall also specify the applicable stimulus presentation control. 4.3.3 Electrical output
When electrical output is used, the manufacturer shall specify the type of electrical signal, output voltage, plug and socket type, minimum load impedance at the specified output voltage, and the time relationship between the output signal and the reflected activation signal. 5 Technical requirements for ear impedance/admittance instrument
This instrument can be designed to measure one or more components of ear impedance/admittance. International units must be used or derived. The measurement unit should be indicated on the front panel of the instrument.
5.1 General requirements
Table 1 gives the mandatory functions of the three types of instruments. The technical requirements for each mandatory function are given in this clause. Type 4 instruments do not specify mandatory functions.
Probe signal pure tone frequency 226Hz
Ear impedance/admittance test system
Measurement plane tympanometric measurement
, ear canal compensation tympanometric measurement
Electrical output and/or recorder
Pneumatic system
Manual pressure change
Automatic pressure change
Electrical output and/or recorder
Acoustic reflex stimulation system
Opposite measurement route
Same measurement route
Acoustic stimulation
Broadband noise
Stimulation level control
1) Indicates that the two must be layered...bzxZ.net
GB/T15953—1995
Table 1 Mandatory functions of ear impedance/admittance meter
2) For type 1 instruments, in addition to the visible indicator, additional functions should be added, 5.2 Measurement System
5.2.1 Units of Measurement
The units of measurement shall be reflected on the instrument front panel or on the device indicating the measurement result. The International System of Units shall be used. 5.2.2 Probe Signal
Types 1, 2 and 3 shall provide a 226 Hz pure tone probe signal. The actual frequency shall not deviate from this nominal frequency by more than ± 3%. When measured in accordance with Chapter 6, the total harmonic distortion shall be less than 5%. If pure tones other than 226 Hz are provided, the frequency accuracy and harmonic distortion shall comply with this requirement.
5.2.3 Probe signal level
For any frequency pure tone, fixed broadband and non-stable probe signal, the signal level required to stimulate the middle ear muscle reflex should be as small as acceptable. For the 226 Hz pure tone probe signal, the sound pressure level measured in Chapter 6 should be 90 dB or less. Note: When the probe signal is used as a reflex activation stimulus, the required signal level is less than the average broadband level of the middle ear acoustic reflex of a sufficient number of normal otological population minus two times the standard deviation. *The definition of normal otological population refers to GR 4854--B4 as "a healthy person without any ear disease symptoms, unconnected ear canal, and no history of excessive noise exposure".
5.2.4 Measurement range
For the 226 Hz probe pure tone, the minimum range expressed in equivalent air volume should be: 0.2 for measuring the plane tympanogram cm~～5cm For the ear canal compensation tympanogram, the 1.2 type is 0--2cm, and the 3 type is 0～1.2cm. The manufacturer shall explain the sensitivity of the acoustic reflex measurement system and the stimulation level that may undergo simulated changes. It may be attached when the reflex-induced stimulation occurs.
GB/T15953—1995
Note: For the simulated measurement of the hard-walled cavity, it is not necessary to provide the conditions that occur in the human ear, so the method of simulating the measurement in the human ear is not specified. 5.2.5 Measurement accuracy
The difference between the impedance/admittance indication value and the actual value shall not exceed ±5% of the equivalent volume or ±0.1cm; or ±10\m\/Pa·8, whichever is larger. The manufacturer shall explain the dynamic and Deviations between static operating modes and measurement methods. 5.2.6 Electrical output
If an electrical output is available, the instrument output should be linear with respect to acoustic impedance/admittance. The total tolerance described in 5.2.5 should be maintained when measuring with an electrical output. If feasible, the full-scale indication of the acoustic impedance indicator should be equivalent to an output voltage of not less than 0.5V and be able to drive a load of 100k.
Note: For single output, zero DC bias is desired. 5.2.7 Time characteristics
The various time response parameters defined in 4.1.7 and measured according to the procedure described in 6.1.2 should not exceed 50ms, and overshoot and undershoot should not exceed 10%.
Note, for measurements above 226 5.3 Pneumatic system
5.3.1 Pressure range
For type 1 and type 2 instruments, the relative pressure range shall be at least +200 daPa to +600 daPa. For type 3, the range shall be specified by the manufacturer, but shall not exceed the maximum limits specified in 5.3.2. 5.3.2 Maximum limits
When measuring with a 0.5 cm3 cavity, the limits of relative pressure shall be -800 daPa and +600 daPa, applicable to all types. All types of instruments shall have an automatic system to prevent the pressure from suddenly reaching or exceeding the limits. 5.3.3 Accuracy of relative pressure indicator
For type 1 and type 2 instruments, the actual relative pressure produced in the 0.5 cm3 to 5 cm3 cavity shall not deviate from the indicated relative pressure by more than ±10 daPa. or ±10%, whichever is greater. For Type 3 instruments, the actual relative pressure produced in a 0.5 cm3 to 2 cm\ cavity shall not deviate from the indicated relative pressure by more than ±10 daPa or ±15%, whichever is greater. These specifications are consistent with the pressure change rate provided. 5.3.4 Rate of pressure change
Type 1 and Type 2 instruments shall provide at least the possibility of changing the relative pressure (increase or decrease) by 50 ±10 daPa/s measured in a 0.5 m3 to 5 crr volume.
Note: Other rates of change may also be provided.
5.3.5 Electrical output
If an electrical output is provided, the output shall be linear in relative pressure. When measuring on an electrical output, the total tolerances described in 5.3.3 shall be maintained. If applicable, the full scale indication of the relative pressure indicator shall correspond to an output pressure of not less than 10.5 V and be capable of driving a load of 100 k.
Note: It is desirable to use a single-ended output with a DC bias. 5.4 Acoustic reflex activation stimulation system
5.4.1 General requirements
Except as provided below, the technical requirements for the acoustic reflex activation stimulation system shall be found in Chapters 7, 8 and 10 of GB7341-87. 5.4.2 Stimulus signal
5.4.2.1 Pure signal
When fixed frequency is used, it should be obtained from the standard audiometry frequency. Type 1 instruments should provide at least 500, 1000, 2000, 10001Iz for contralateral and ipsilateral acoustic reflex stimulation and measurement. Type 2 instruments should provide at least 500.1000.2000Hz for contralateral or ipsilateral acoustic reflex stimulation and measurement. Yan Jian
5.4.2-2 Pure harmonic distortion
GB/T15953-1995
Table 2 gives the maximum total harmonic distortion corresponding to each frequency and stimulation level. For higher stimulation levels, the total harmonic distortion of on-ear headphones should not exceed 5%, and that of insert or probe headphones should not exceed 10%. Table 2 Pure tone harmonic distortion
Frequency, Hz
Stimulus level
Hearing level, dB
Sound pressure level, dB
Maximum total harmonic distortion
On-ear headphones
500--4 000
Insert earphones
1000--3 000
1 If the maximum output of the instrument is less than the hearing level or sound pressure level given in Table 3, the requirements given in this table shall apply to the maximum output of the instrument. 2 For any given instrument, the hearing level and sound pressure level given in the table may be selected and they do not represent equivalence. For the values ​​of on-ear headphones, refer to GB4854. For the sound pressure level values ​​of insert earphones, refer to SJ/Z9144 acoustic coupling chamber or SJ/Z9150 blocked ear simulator. The manufacturer shall state which one is selected. 5.4.2.3 Broadband Noise
If broadband noise is provided, the spectral levels measured acoustically for on-ear headphones shall be within ±5 dB relative to the 1000 Hz output level over the frequency range of 250 Hz to 4000 Hz, and within ±10 dB for insert or arm-reaching headphones. 5.4.2.4 Other Stimuli
If other types of stimuli are provided, the manufacturer shall describe their characteristics. 5.4.3 Stimulus Level Control
5.4.3.1 Markings
The front panel, stimulus level control, or linear display of an instrument calibrated in accordance with this standard shall be identifiable. For on-ear headphones, it should be marked as "hearing level dB" according to GB4854. For insert headphones, it should be marked as "sound pressure level dB" or "hearing level dH". The manufacturer should explain the process used to derive the reference equivalent listening sound pressure level. The maximum level of each pure tone frequency and each broadband noise should be indicated. For other headphones specified in GB4854, the reference equivalent listening sound pressure level can be determined by the diameter sequence recommended in Appendix A2 of GB485-84. 5.4.3.2 Hearing separation and minimum range
For type 1 and type 2 instruments, the stimulus level control should at least include the range listed in Table 3. The stimulus level reading should be expressed in intervals of 5dI3 or less.
Stimulation level
Hearing level range for on-ear headphones
Table 3 Minimum hearing level range or sound pressure level range for different stimuli 250 Hz
Hearing level range for insert or probe earphones
Also sound pressure level range for insert or probe earphones
*In the case of noise, it can also be specified according to the sound pressure level. 500Hz-2000Hz
50~320
50~100
60~110
4 000 Hz
50--120
51~-80
6 000 H
50~-100
50~115
1 The noise stimulation of the earphones specified in this table, as well as the pure tone and noise band stimulation of the plug-in or probe earphones, can be measured by the hearing level or sound pressure level d13. If it can be used to select the effect of the hearing level and its starting point, the stimulation level can be higher than the given value for children. 5.4.3.3 Stimulation level control accuracy
CB/T15953—1995
The sound pressure level generated by the stimulation transducer, for earphones, in the frequency range of 250Hz~～4000 Hz, any frequency and any stimulus level control, the deviation from the marked value should not exceed ±3dB, at 6000Hz and noise stimulus should not exceed ±5dB; for insert or probe earphones, the frequency range of 600Hz to 2000Hz should not exceed ±5dB, at 4000Hz should not exceed +5/-10dB. 5.4.4 Stimulus Presentation Control
The instrument should use a manual or automatic switch to provide the stimulus signal. The switch and its related circuits should reflect the stimulus signal, not the instantaneous or other noise.
5.4.4.1 "On"-off" and signal-to-noise ratio "On"-off" and signal-to-noise ratio should be at least 70dB. However, when expressed in A-weighted residual sound pressure level, it should not exceed 25dB when the stimulus presentation switch is in the "off" position
5.4.4.2 Rise-fall time
a) On state
When the stimulus presentation control is switched to the "on" state, the time required for the sound pressure level generated by the transducer to reach -1dB relative to its last stable level, calculated from the moment the stimulus presentation control is changed, should not exceed 100ms. The time required for the sound pressure level to gradually decrease from -20dB to -1dB relative to its last stable level should not be less than 5ⅡS. The sound pressure level produced by the transducer shall have a pure tone rise or fall of less than 1 dB relative to the steady-state level in the “on” position.
b) “off” state
When the stimulus presentation control is switched to the “off” position, the time required for the sound pressure level produced by the transducer to fall to -20 dB relative to the stable level in the “on” position shall not exceed 100 ms, calculated from the moment the stimulus presentation control is changed. The time required for the sound pressure level to gradually fall from -1 dB to -20 dB relative to the stable level in the “on” position shall not be less than 5 ms. 5.4.4.3 Pulse stimulus signal
If a pulse stimulus signal is used, the manufacturer shall specify the time characteristics of the signal. 5.4.5 Electrical output
When an electrical output is present, it shall have an envelope that reflects the reflex activation stimulus signal. 6 Performance test method
The following procedure is used to ensure that the instrument can meet this standard and is not used for routine calibration. For this purpose, the manufacturer shall provide simplified procedures with appropriate tolerances to ensure that the instrument meets the specifications.
6.1 Measuring system
6.1.1 Impedance/admittance indicator
The probes shall be connected in sequence to a set of air-tight, hard-walled cavities. The number and shape of the cavities refer to Chapter 7. The test shall be carried out at a pure tone frequency of 226 Hz.
The impedance/admittance indicator shall be connected to the ambient pressure and the test cavity reading corrected for temperature and atmospheric pressure according to the formula in 3.10. Note: For other probes, the manufacturer shall specify suitable test objects that can represent the extreme parts of the measurement range and at least one intermediate value. 6.1.2 Total time characteristics
When measuring the total time characteristics shown in Figure 1, the probe tube should be connected to a 2cm2" hard-walled cavity. The miniature sound source excited by the electrical signal derived from the probe signal should be connected to the cavity close to the probe. Through a suitable switching circuit, the excitation of the sound source should reach a signal level equivalent to a cavity reduction of 0.2cm. According to Figure 1, the response time is measured by presenting a stimulus change with a rise and fall time of 5s in the equivalent volume and a duration of at least 1s. The measured electrical output should be connected to the specified minimum load impedance and connected to the - channel of a dual-trace oscilloscope or a YT recorder with an upper frequency limit of at least 20Hz-3dB).
GB/T15953-1995
90% or 42
The dotted line represents overshoot and undershoot, expressed as a percentage: ×1 00 and ×100
×100 or will
Figure 1 Test cavity response to segmented input changes, measured from T. The total time characteristics of AY.
T, initial latency, defined as the time from the start of the simulated input impedance/admittance segment to the measured steady-state impedance change of 10%, in seconds:
Rise time: defined as the time from the measured steady-state impedance/admittance change from 10% to 90%, in seconds; T, terminal latency: defined as the time from the simulated input impedance/admittance segment end change to the measured stable impedance/admittance change of 90%:
Fall time: defined as the time from the simulated input impedance/admittance segment end change to the measured stable impedance/admittance change of 90%, in seconds; T, terminal latency: defined as the time from the simulated input impedance/admittance segment end change to the measured stable impedance/admittance change of 90% to 10%, in seconds; T, fall time: defined as the time from the measured stable impedance/admittance change from 90% to 10% after the initial impedance change ends, in seconds, input impedance/admittance simulated segmented change AZ, AY, the stable value change of impedance/admittance Z when the simulated change is switched to "on" or "off". ,AY, when the analog input changes and switches to "on", before reaching stability, the overshoot of the transient simulation response is measured; A2,,AY, when the analog input changes and switches to "off", before reaching stability, the overshoot of the transient simulation response is measured. The overshoot and undershoot are expressed as a percentage of the steady-state value change shown in Figure 1. 6.2 Probe signal
6.2.1 Probe signal harmonics
The frequency of the pure tone probe signal shall be measured electronically, and the inaccuracy of the measuring instrument shall be better than ±1 Hz or ±0.5%, whichever is greater. For other probe signals other than pure tone, the probe tube must be air-sealed to the $J/Z9144 joint cavity, and the top of the probe head shall be level with the cavity wall, see SJ/2 9144-87 Figure 3.
6.2.2 Probe signal level and harmonics are distortedInput impedance/admittance simulation segmented change A2, A3, A4, stable value change of impedance/admittance when the simulation input change is switched to "on" or "off". A5, A6, overshoot of transient simulation response before reaching stability when the simulation input change is switched to "on". A7, A8, overshoot of transient simulation response before reaching stability when the simulation input change is switched to "off". Overshoot and undershoot shall be expressed as a percentage of the steady-state value change shown in Figure 1. 6.2 Probe signal
6.2.1 Probe signal harmonics
The frequency of pure tone probe signal shall be measured electrically, and the uncertainty of the measuring instrument shall be better than ±1 Hz or ±0.5%, whichever is greater. For probe signals other than pure tone, the probe tube must be air-sealed to the $J/Z9144 joint cavity, and the top of the probe head shall be flush with the cavity wall, see Figure 3 of SJ/2 9144-87.
6.2.2 Probe signal level and harmonic distortionInput impedance/admittance simulation segmented change A2, A3, A4, stable value change of impedance/admittance when the simulation input change is switched to "on" or "off". A5, A6, overshoot of transient simulation response before reaching stability when the simulation input change is switched to "on". A7, A8, overshoot of transient simulation response before reaching stability when the simulation input change is switched to "off". Overshoot and undershoot shall be expressed as a percentage of the steady-state value change shown in Figure 1. 6.2 Probe signal
6.2.1 Probe signal harmonics
The frequency of pure tone probe signal shall be measured electrically, and the uncertainty of the measuring instrument shall be better than ±1 Hz or ±0.5%, whichever is greater. For probe signals other than pure tone, the probe tube must be air-sealed to the $J/Z9144 joint cavity, and the top of the probe head shall be flush with the cavity wall, see Figure 3 of SJ/2 9144-87.
6.2.2 Probe signal level and harmonic distortion
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