Czech Metrology Institute  
Okružní 31, 638 00 Brno  
 
 
 
1. ------IND- 2018 0330 CZ - EN- ------ 20180803 --- --- PROJET 
Executive summary for the EC (not part of this legislation)  
Pure-tone audiometers are placed on the market and put into use in the Czech Republic pursuant to 
Council Directive  93/42/EEC of 14  June 1993 concerning medical devices, as amended by 
Directive  98/79/EC of the European Parliament and of the Council of 27  October  1998, 
Directive  2000/70/EC of the European Parliament  and of the Council of 16  November  2000, 
Directive  2001/104/EC of the European Parliament and of the Council of 7  December  2001, 
Regulation (EC) No  1882/2003 of the European Parliament and of the Council of 
29 September  2003, and Directive  2007/47/EC of th e European Parliament and of the Council of 
5 September  2007. Once they have been put into use, they become subject to national metrological 
regulation – verification at specified intervals.  
This notified legislation only applies to the verification of mea suring instruments that have already 
been put into use. It does not concern placing them on the market or putting them into use.  
(End of executive summary.)  
 
Contact person: Mgr. Tomáš 
Hendrych  
Phone: +420  545 555 414 
PUBLIC DECREE  
As the authority with substantive and territorial jurisdiction in the matter of laying down metrological 
and technical requirements for legally controlled measuring instruments and stipulating the testing 
methods for type approval and verification of legally controlled measurin g instruments pursuant to 
§ 14(1) of Act No  505/1990 on metrology, as amended (hereinafter the Metrology Act), and in 
accordance with the provisions of §  172 et seq. of Act No  500/2004, the Administrative Procedure 
Code (hereinafter the APC), on 29  Februar y 2016, the Czech Metrology Institute (hereinafter the CMI) 
commenced ex officio proceedings pursuant to §  46 of the APC and, on the basis of supporting 
documents, issues the following:  
I. 
DRAFT GENERAL MEASUR E 
ref. No: 0111 -OOP -C064 -16 
laying down the met rological and technical requirements for legally controlled measuring 
instruments, including testing methods for type approval and verification of the following legally 
controlled measuring instruments:  
pure -tone audiometers  
 General Measure No 0111 -OOP -C064 -16 
 
2 This legislation lays down the  metrological and technical requirements for pure -tone audiometers to be 
applied in subsequent verification of these instruments after they have been placed on the market or 
put into use. These requirements comply with the requirements of special legislati on1 and apply the 
relevant requirements of harmonised standards.  
The verification of pure -tone audiometers type approved under the Metrology Act, i.e. prior to the 
transposition of Council Directive  93/42/EEC, as amended, into Czech law, shall be subject t o 
metrological requirements applicable at the time they were put into circulation.  
1 Basic definitions  
For the purposes of this general measure, terms and definitions pursuant to VIM and VIML2 and the 
terms and definitions below shall apply.  
1.1 
pure -tone audiometer  
an instrument for the measurement of hearing for pure tones and in particular of the threshold of 
hearing  
1.2 
artificial ear  
a device for the calibration of earphones that presents an acoustic impedance load to the earphones 
equivalent to that of the average human ear of an adult. The artificial ear is equipped with a calibrated 
microphone for measuring sound pressure generated by earphones.  
1.3 
acoustic coupler  
a cavity of predetermined shape and volume used for the calibration of earphones in conjunction with 
a calibrated microphone adapted to measure the sound pressure developed in the cavity.  
1.4 
ear simulator  
a general term used to describe devices such as artificial ears (1.2) and acoustic couplers (1.3), which 
are used to measure sound pre ssure at the output of earphones.  
1.5 
mechanical coupler  
a device equipped with an electromechanical transducer allowing the alternating force level at the 
surface contact between vibrator and mechanical coupler to be established; it is designed to present  a 
specified mechanical impedance to the vibrator applied with a specified static force.  
1.6 
reference equivalent threshold sound  pressure level (RETSPL)  
the mean value of the equivalent threshold sound pressure level at a specified frequency of a 
sufficie ntly large number of ears of otologically normal persons of both sexes aged between 18 and 30 
                                                      
1 Government Regulation No  54/2015 laying down technical requirements for medical devices  
2 TNI 01 0115 International Vocabulary of Metrology – Basic and General Concepts and Associated Terms 
(VIM) and International Vocabulary of Legal Metrology (VIML) are part of the technical harmonisation 
compendium ‘Terminology in the field of metrology’, which is publicly available at www.unmz.cz  General Measure No 0111 -OOP -C064 -16 
 
3 years inclusive, expressing the threshold of hearing in a specified acoustic coupler or artificial ear for a 
specified type of earphones.  
1.7 
reference equivalent  threshold force level (RETFL)  
the mean value of the equivalent threshold force levels at a specified frequency of a sufficiently large 
number of ears of otologically normal persons of both sexes aged between 18 and 30 years inclusive, 
expressing the thres hold of hearing on a specified mechanical coupler for a specified configuration of 
bone vibrator.  
1.8 
pure -tone hearing level (HL)  
the sound pressure level or the vibratory force level at a specified frequency for a specific type of 
earphones or vibrator a nd for a specified manner of application produced by the earphones or vibrator 
in a specified ear simulator or mechanical coupler minus the appropriate reference equivalent 
threshold sound pressure level or reference equivalent threshold force level.  
2 Met rological requirements  
The metrological requirements are based on the requirements of special legislation1 and the 
requirements and recommendations of the International Organisation of Legal Metrology.  
The verification of measuring instruments type approve d prior to the entry into force of the Metrology 
Act shall be subject to the metrological requirements applicable at the time they were put into 
circulation3. 
2.1 Pure -tone audiometers  
2.1.1. Operating conditions  
Specified combinations of temperature, relative humidity and static pressure:  
Air temperature:  15–35 °C 
Relative humidity:  30–90 % 
Static pressure:  98–104 kPa 
2.1.2 Measuring interval  
The measuring intervals for each class of pure -tone audiometers are given in Table  1 and for extended 
high-frequency audiometers in Table  2. 
                                                      
3 OIML  R 104 ‘Pure -tone audiometers’ – publicly available at  www.oiml.org  General Measure No 0111 -OOP -C064 -16 
 
4 Table  1 Minimum number of fixed frequencies and minimum range of hearing levels.  
Frequency  
(Hz) Hearing levels *) 
(dB) 
Class  1 Class  2 Class  3 Class  4 
Air 
conduction  Bone 
conduction  Air 
conduction  Bone 
conduction  Air 
conduction  Bone 
conduction  Air 
conduction  
125 70 - 60 - - - - 
250 90 45 80 45 70 35 70 
500 120 60 110 60 100 50 70 
750 120 60 - - - - - 
1 000  120 70 110 70 100 60 70 
1 500  120 70 110 70 - - - 
2 000  120 70 110 70 100 60 70 
3 000  120 70 110 70 100 60 70 
4 000  120 60 110 60 100 50 70 
6 000  110 50 100 - 90 - 70 
8 000  100 - 90 - 80 - - 
*) The maximum hearing level shall be at least equal to the values given in this table.  
The lowest hearing level shall be -10 dB or lower.  
 
Table  2: Extended high-frequency audiometers – minimum range of hearing levels.  
Frequency  
(Hz) 8 000(*) 9 000  10 000(*) 11 200  12 500(*) 14 000(*) 16 000(*) 
Hearing levels**) 
(dB) 100 90 90 80 70 70 60 
**) The minimum hearing levels shall be -10 dB or lower at all frequencies.  
(*) These measuring signal frequencies are mandatory.  
2.1.3 Maximum permissible error  
2.1.3.1 Accuracy of sound pressure level and vibratory force level settings  
The sound pressure level minus the reference equivalent threshold shall differ by not more than 
3.7 dB from the indicated value at indicated frequencies in 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 the tolerance of 6.5 dB. 
The force level produced by the bone vibrator minus the reference equivalent threshold force level 
shall differ by not more than 5.5 dB in the frequency range 125  Hz to 4  kHz a nd by not more than 
7.0 dB at higher frequencies.  
If more than one channel of the measurement signal or noise is connected simultaneously to a single 
transducer, the output level of either signal (or noise) from the transducer shall not differ by more tha n 
1.7 dB from the level obtained when only one channel is connected. This requirement shall be met at General Measure No 0111 -OOP -C064 -16 
 
5 frequencies from 125  Hz to 4  kHz. A tolerance of 3.2 dB at frequencies from 5  kHz to 8  kHz and 
3.5 dB at frequencies from 8  kHz to 16  kHz shall be requ ired. This shall apply to hearing levels up to 
20 dB below the maximum output level.  
2.1.3.2 Accuracy of masking level settings  
The level of the masking sound produced by an earphone shall not differ from the indicated value by more 
than 
6
4
  dB. 
2.1.3.3 Harmonic distortion  
The maximum total harmonic distortion shall not exceed the values given in Table  3. 
Table  3 Maximum permissible acoustic total harmonic distortion for supra -aural, circumaural and 
insert earphones and bone vibrators.  
 Air conduction  Bone conduction  
Frequency range  
(Hz) 125 to 250  315 to 400  500 to 5  000 250 to 400  500 to 800  1 000 to 
4 000 
Hearing level *) 
(dB) 75 90 110 20 50 60 
Total harmonic 
distortion  (%) 3 3 3 6 6 6 
*) Or the maximum output level of the audiometer, whichever is lower. For circumaural and insert earphones, 
the hearing level shall be 10  dB lower than the level specified in the table.  
2.1.3.4 Accuracy of frequency settings  
For fixed  frequency audiometers,  the frequencies shall be equal to the stated values with the following 
tolerances:  
Class  1 and 2:  1.5 % 
Class  3 and 4:  2.5 % 
For continuous sweep frequency audiometers, the frequency of the test tone shall agree with the value 
indicated in the audiogr am with an accuracy of 5.5 %. 
2.1.3.5 Accuracy of control  
The difference (in decibels) between the measured difference and indicated difference between two 
subsequent hearing level settings shall be less than or equal to the lower of the following values:  
 three -tenths of the indicated difference in decibels, or  
o 1.5 dB for hearing level settings between -10 dB and 0  dB; 
o 1.4 dB for hearing level settings between 0  dB and 45  dB; 
o 1.2 dB for hearing level settings at 45  dB or higher.  
2.1.3.6 Test tone on/off ratio for audiometers with manual control  
With the test tone switch in the OFF position and the hearing level control set at 60  dB or below, the 
output shall be at least 10  dB below the reference equivalent threshold level. At higher hearing level 
settings  and with the test tone switch still in the OFF position, the output shall not rise by more than 
10 dB for each 10  dB increase in the hearing level setting above 60  dB. General Measure No 0111 -OOP -C064 -16 
 
6 2.1.3.7 Static force  
The headband shall generate static force:  
 earphones:  4.5 N ± 0.5  N 
 bone vibrator:  5.4 N ± 0.5  N 
3 Technical requirements  
The technical requirements are based on the requirements of special legislation1. 
The verification of measuring instruments type approved prior to the entry into force of the Metrology 
Act shall be s ubject to the technical requirements applicable at the time they were put into circulation.  
3.1 Requirements for specific classes of fixed frequency audiometers  
Requirements for minimum facilities for the following four classes of audiometers are given in 
Table  4. 
Class  1  Audiometers for advanced clinical/research work  
Class  2 Audiometers for clinical work  
Class  3 Audiometers for basic diagnostics  
Class  4 Audiometers for screening/monitoring  
Table  4 Minimum facilities of fixed frequency audiometers.  
Facilities  Class  1 Class  2 Class  3 Class  4 
Air conduction:  
- two earphones  
- additional insert earphone   
YES  
YES   
YES   
YES   
YES  
Bone conduction  YES  YES  YES   
Hearing levels and test 
frequencies (see Table  2 and 
Table  3)     
Narrow -band masking noise  YES  YES  YES   
External signal input  YES  YES    
Test tone switching  
- tone presentation  
- tone interruption  
- pulsed tone   
YES  
YES  
YES   
YES  
YES  
YES   
YES  
 
  
YES I. 
YES II. 
 
Masking method  
- contralateral earphone  
- ipsilateral earphone  
- bone vibrator   
YES  
YES  
YES   
YES   
YES   
Reference tone III. 
- alternate presentation  
- simultaneous presentation   
YES  
YES   
YES    
Subject response system  YES  YES  YES  YES b 
Electrical signal output  YES  YES    
Signal indicator  YES  YES    General Measure No 0111 -OOP -C064 -16 
 
7 Acoustic monitor  for the tone 
signal  
- pure tones and noise  
- external input   
 
YES  
YES     
Speech communication  
- operator with subject  
- subject with operator   
YES  
YES   
YES    
NOTE  The extended high -frequency range (EHF range) is optional for all four classes of audiometers.  
I. Not mandatory for automatic recording audiometers, except for calibration purposes.  
II. Not mandatory for manual audiometers.  
III. The minimum requirement is for the presentation of reference tones of the same frequency as the test tones.  
3.2 General safety requirements  
Audiometers shall conform to safety requirements.  
3.3 Acoustic safety requirements  
A non -auditory warning indication to the operator is required for all hearing level settings above 100  dB. 
3.4 Environmental conditions  
The technical requirements shall be met for the following specified combinations of temperature 
within the range of 15  °C to 35  °C, relative humidity within the range 30  % and 90  % and static 
pressure within the range 98  kPa and 104  kPa. 
3.5 Warm -up time (5.4)  
The perfo rmance requirements shall be met after the stated warm -up time has elapsed and after any 
setting -up adjustments have been carried out in accordance with the manufacturer’s instructions.  
The minimum warm -up time of the instrument shall be specified by the m anufacturer. However, if the 
audiometer has been kept at the ambient temperature of the test environment, the warm -up time shall 
not exceed 10  minutes.  
3.6 Power supply variation  
3.6.1 Interruption of power supply  
In the event of a complete power supply fa ilure of up to five  seconds, the audiometer shall be able to 
revert to a condition ensuring that the subject’s hearing is not endangered and the results obtained are 
not incorrect.  
3.6.2 Mains operation  
Within the limits of 10 % of the stated mains supply  voltage and  5 % of the stated mains frequency, 
the technical requirements shall be met for any long -term combined deviation of supply voltage or 
frequency of the mains which is the least favourable.  
3.6.3 Battery operation  
The manufacturer shall specify the limits of battery voltage within which the technical requirements 
will be complied with. The audiometer shall be fitted with a suitable battery voltage indicator so that it General Measure No 0111 -OOP -C064 -16 
 
8 is always clear that the battery voltage is within the specified limits. The te chnical requirements for the 
audiometer shall be complied with at all battery voltages within the specified limits.  
3.6.4 Other power supply sources  
If the audiometer is powered by means other than by mains or battery, the manufacturer shall specify 
the type of power supply, its characteristics and tolerances within which the specifications of the 
audiometer will be met.  
3.7 Electromagnetic compatibility (EMC)  
The unwanted sound from any air conduction transducer shall not exceed a hearing level 
correspon ding to 80  dB during and as a result of any electromagnetic compatibility immunity tests and 
under any test conditions of electromagnetic compatibility.  
3.8 Unwanted sound  
3.8.1 Unwanted sound radiated by an audiometer  
Where audiometers are intended to be used with the subject in the same room, no sound generated due 
to the operation of the audiometer’s controls during the actual listening test or radiated from the 
audiometer or radiated from any part of a computer system used in conjunction with the audiom eter 
may be audible at any hearing level control setting up to and including 50  dB. 
3.9 Interface connections  
No unintentional change of the audiometer’s calibration shall be possible via any interface.  
4 Measuring instrument markings  
The following information shall be provided on audiometers:  
 the manufacturer’s name;  
 model, class (see Chapter  3.1); 
 serial number.  
These identification details shall also be provided on the measuring signal transducers.  
The left and right earphones shall also be readil y identifiable. If colour -coded, the left earphone shall 
be blue and the right earphone shall be red.  
Any inscriptions and markings provided on the audiometer or, if applicable, on the tone signal 
transducers shall be clearly visible and legible under norm al operating conditions and shall not impede 
reading the measuring instrument.  
5 Type approval of the measuring instrument  
Pure-tone audiometers are not subject to type approval under the provisions of the Metrology Act.  
The measuring instruments shall be placed on the market and put into use after conformity assessment 
in accordance with special legislation1. 
6 Initial verification  
The measuring instruments shall be placed on the market and put into use after conformity assessment 
in accordance with specia l legislation1. General Measure No 0111 -OOP -C064 -16 
 
9 7 Subsequent verification  
7.1 In general  
7.1.1 Overview of the tests conducted  
Subsequent verification of pure -tone audiometers shall comprise the following tests conducted 
sequentially:  
a) visual inspection,  
b) accuracy test.  
7.1.2 Test equipmen t 
The following equipment shall be used for the tests:  
a) ear simulator, mechanical coupler, sound level meter or sound analyser with one  third octave 
filters, multimeter, apparatus for measuring static force;  
b) thermometer with a measuring range of 15 –35 °C, hygrometer, barometer.  
7.2 Visual inspection  
The purpose of visual inspection shall be to check that:  
 the audiometer is not mechanically damaged and is free of defects visually detectable without 
the use of any aids;  
 the transducer cables are not obviously  damaged;  
 the audiometer has the appropriate markings.  
If the pure -tone audiometer fails to meet visual inspection requirements, no further tests are 
performed.  
7.3 Accuracy test  
All the tests referred to in Article  7.3 shall be conducted under the operating conditions referred to in 
Article  2.1. 
7.3.1 Accuracy of sound pressure level and vibratory force level settings  
The test shall be conducted by measuring the output of each earphone, at all available frequencies, 
using the specified ear simulator  with the hearing level set at 70  dB or at the maximum level, 
whichever is lower. For bone vibrators, the hearing level shall be set at 30  dB or at the maximum 
value, whichever is lower  and the measurement shall be performed on the mechanical coupler.  
7.3.2 Accuracy of masking level settings  
The test shall be conducted in the same manner as under 7.3.1.  
7.3.3 Harmonic distortion  
The test shall be conducted at the hearing levels given in Table  3 or with the audiometer set at the 
highest hearing level, whiche ver is lower. Measurement of harmonics above 16  kHz is not required. In 
the case of air conduction, the distortion shall be measured acoustically on an ear simulator of the type 
used when specifying the reference equivalent threshold levels. In the case of  bone conduction, the 
distortion shall be measured on the mechanical coupler.  
7.3.4 Accuracy of frequency settings  
The test of accuracy of frequency settings shall be conducted for all used frequencies by direct 
measurement using a reader or a multimeter.  General Measure No 0111 -OOP -C064 -16 
 
10 7.3.5 Accuracy of control  
The test of accuracy of hearing level control shall be conducted at 1  kHz; if the audiometer is equipped 
for an extended high -frequency range, an additional test at 8  kHz shall be conducted. As far as 
possible, the tests shall be conducted acoustically. If electrical measurements are made, it is 
recommended to use the Y splitter where the common part is connected to the audiometer output and 
the multimeter and earphones are connected to the splitter.  
7.3.6 On/off signal ratio  
The t est of the on/off signal ratio for manual audiometers shall be conducted by electrical 
measurement using a Y splitter.  
7.3.7 Static force  
7.3.7.1 Headband for supra -aural and circumaural earphones  
The test shall be conducted by stretching the headband with  the earphones horizontally to a length of 
145 mm, while adjusting the height of the headband to a vertical distance of 129  mm measured 
between the centre (top) of the headband and the line passing through the centres of the earphones. 
The dimensional tole rance is ±5  mm. 
7.3.7.2 Headband for bone vibrators  
The test shall be conducted as described in 7.3.7.1 with the difference that when placing the bone 
vibrator on the forehead, the distance shall be 190  mm with a tolerance of ±5  mm. 
8 Notified standards  
For the purposes of specifying the metrological and technical requirements for measuring instruments 
and specifying the testing methods for their type approval and verification stemming from this general 
measure, the CMI shall notify the Czech technical st andards, other technical standards or technical 
documents of international or foreign organisations, or other technical documents containing more 
detailed technical requirements (hereinafter notified standards). The CMI shall publish a list of these 
notifi ed standards attached to the relevant measures, together with the general measure, in a manner 
accessible to the public (on www.cmi.cz ). 
Compliance with notified standards or parts thereof is considered, to the extent and under the 
conditions stipulated by a general measure, to be compliance with the requirements stipulated by this 
measure to which these standards or parts thereof apply.  
Compliance with notified standards is one way of demonstrating compliance with the requirements. 
These requirements may also be met by using another technical solution guaranteeing an equivalent or 
higher level of protection of legitimate interests.  
II. 
GROUNDS  
The CMI has issued this general measure laying down metrological and technica l requirements for 
legally controlled measuring instruments and tests for verification of these legally controlled 
measuring instruments in accordance with §  14(1)(j) of the Metrology Act to implement §  9(1) and 
§ 11a(3) of the Metrology Act.  
Implementing Decree No  345/2002 specifying measuring instruments for mandatory verification and 
measuring instruments subject to type approval, as amended, classifies ‘pure -tone audiometers’ under 
item 6.1.3 of the annex entitled ‘List of the types of legally controlle d measuring instruments’ as 
measuring instruments subject to verification.  General Measure No 0111 -OOP -C064 -16 
 
11 The CMI has issued this draft general measure laying down metrological and technical requirements 
and testing methods for the verification of these legally controlled measuring inst ruments to 
implement §  9(1) and §  11a(3) of the Metrology Act for this type of measuring instruments.  
This legislation ( general measure) will be notified in accordance with Directive (EU)  2015/1535 of the 
European Parliament and of the Council of 9  Septemb er 2015 laying down a procedure for the 
provision of information in the field of technical regulations and of rules on Information Society 
services.  
III. 
INSTRUCTIONS  
In accordance with §  172(l), in conjunction with §  39(l) APC, the CMI has stipulated a time limit for 
comments of 30  days as of the date of posting on the official notice board. Comments submitted after 
this time will not be considered.  
The persons concerned are hereby invited to comment on this draft general measure. With a view to 
the prov isions of §  172(4) APC, comments shall be submitted in writing and meet the requirements for 
submissions in accordance with §  37 APC.  
The comments shall include the particulars referred to in §  37(2) APC and clearly state the following: 
who is making the c omments; which general measure they concern; to what extent the comments 
challenge the measure; how the general measure runs contrary to legislation or how the general 
measure or the procedure that preceded it is inaccurate; which matters the comments conc ern and what 
is being proposed. Said comments must also identify the administrative authority to which they are 
addressed and be signed by the person making them.  
The supporting documents for this draft general measure may be consulted at the Czech Metrolo gy 
Institute, Legal Metrology Department, Okružní 31, 638 00 Brno, after making arrangements by 
telephone.  
This general measure shall be posted for 15  days.  
 
 
 
 
 
 ...…………………………..............  
RNDr. Pavel Klenovský  
Director -General  
Person responsible for accuracy: Mgr. Tomáš Hendrych  
Posted on: 27  July 2017  
Signature of the authorised person confirming posting:  ....................................................  
Removed on:  
Signature of the authorised person confirming removal:  ........................... .........................