Portable Audiometer Calibration System March 2012 BRK_4135 BRK 4135

User Manual: BRK_4135

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Portable Audiometer
Calibration System
Type 9729-W-011
… Easy, flexible
and reliable

PRODUCT DATA
The Type 9729-W-011 Portable
Audiometer Calibration System is
an easy, flexible and reliable solution for automated calibration of
audiometers to IEC and ANSI
standards.
The system performs the tasks
ranging from basic standard audiometer testing with fully automated procedures to advanced
customized tests.
Audiometer certification is the
primary focus, but the system is
designed to accommodate the
everyday needs of hospitals and
clinics as well as those of calibration and metrology laboratories.
Other fields of use are audiometer
research & development and factory production testing.
The system is build around the
powerful sound level meter and
analyzer Type 2250. It utilizes the
precision of this Class 1 measuring
instrument and experience in calibration to provide simplicity of
use.
The Type EN-2252 software
with integrated database takes
care of test procedure execution
as well as all house-keeping data
including client e-mail reminders
for next calibration.

USES

AND

The calibration system is not
limited to any specific brand or
type of audiometer, but can calibrate any audiometer that complies with relevant ISO standards.
The interface with the variety
of audiometers is secured by using
Brüel & Kjær family of top-class
couplers, such as 2cc Click-on

Coupler Type 4946, the artificial
ears Type 4152 or 4153 and the
artificial mastoid Type 4930. The
system can be configured for inhouse calibration services or production tests as well as for use in
the field, without compromising
neither accuracy nor stability.

FEATURES

Uses
 Calibrate any type of audiometer fulfilling IEC
60645 and ISO 389 series standards as well as
ANSI/ASA S3.6 and S3.7.
 Calibrate Headphones, Inserts, HF phones, Bone
Oscillators and Tympanometers
 Free field calibration (audiometry test room)

 Semi- or fully automated procedures execution.
 Automatic correction for microphone and artificial

Features
 Calibration procedures based on international
standards for air conductive and bone conductive
transducers.
 Multiple test procedures.

 Tracking of calibration equipment inventory and

mastoid sensitivity deviations.

 Data on operators, customers, audiometers, tests
and test equipment is managed in one database.

 Data can be retrieved by a range of query parameters.

calibration date.

 Audiometer adjustment instructions
 Customized calibration reports
 Calibration reminder via e-mail.

Portable Audiometer Calibration System

Type 9729-W-011

Calibration..?
The basic aim of acoustic
audiometer calibration is to
define the audiometric zero for
the chosen earphone. This can
be performed using human
volunteers or an artifical ear.
There are different types of
audiometer output transducers:
1. Ear phones
2. Bone vibrator
3. Loud speaker (free-field)
Output transducers for audiometers cannot be replaced or
changed without calibrating
the whole equipment.
Calibration of the audiometer involves calibration of the
audiometer proper, of ear phones, and of bone vibrators.
The calibration procedure
and set-up for bone vibrators
is the same as for earphones
except for the basic measuring
device.

Figure 1.
Main menu of the EN-2252 software
—a simple and intuitive user interface with all functionalities

For absolute acoustic calibration the audiometer should be
calibrated using an artificial ear, a
special measuring microphone
designed for that purpose and a
known sound pressure level.
Accurate and reliable measurements are fundamental to characterise and quantify hearing loss,
and consequently for selection of
hearing aids and for general
Audiometer Calibration
health and safety monitoring.
The purpose of any calibration
measurement is to check that the Prober calibration ensures that the
measurement equipment is meas- measurements are consistent, no
matter where the they are carried
uring correctly. Regular testing
and calibration of an audiometer is out.
The system calibrates audiorequired to maintain maximum
meters using an ear simulator
measurement accuracy.

system. It includes an artificial ear
for testing air-conduction hearing
mechanisms. This device consist
of a calibrated microphone with an
associated coupling volume open
on one side allowing application of
headphones when testing.
For testing bone-conduction
hearing mechanisms, an artificial
mastoid is utilised. This device
uses a series of rubber layers to
couple the bone-vibrator to a
force transducer. The device
mimics the way in which sound is
transferred through the mastoid
part of the human temporal bone
to which the bone-vibrators are
applied when testing.

Figure 2.
Set-up of 9729-W-011
Portable Audiometer
Calibration System

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2

Type 9729-W-011

Portable Audiometer Calibration System

System Instrumentation
The calibration system is based on Hand-held Acoustic Analyzer Type 2250 and the
Audiometer Calibration Software Type EN-XXXX.

Acoustic Analyzer
The 9729-W-011 Portable
Audiometer Calibration
System is based on the
Type 2250 Hand-held
Acoustic Analyzer. Type 2250
is a compact and robust handheld instrument, which can host
a number of software modules.

Sound Calibrator
Sound Calibrator Type 4231 is a
pocket-sized, battery operated
class 1 sound source. The
calibration frequency is 1000Hz (the
reference frequency for the standardised
international weighting networks) with a
calibration pressure of 94 ±0.2 dB re 20 μPa is
equal to 1 Pa or 1N/m2.
Artificial Mastoid
Artificial Mastoid Type 4930 is designed for the
calibration of bone conduction hearing aids and
bone vibrators used in audiometry. It
mechanically simulates the
human head,
incorporating a
built-in force
transducer to
monitor the
output of the
device to be
calibrated. The
artificial
mastoid
ensures
longterm
stability and accurate correspon-dence with the
mechanical characteristics of the human mastoid.
Coupler
Type 4946 2 cc Click-on Coupler is intended for
measurements on all types of headphones and
hearing aids. The design is optimised for
quick and easy use in the laboratory and
the field. It fulfils the requirements of the
ANSI S3.7 (1995) and IEC 60318-5 (2006)
standards. A wide range of ear-mould simulators
click on to the coupler body, making changing to
different headphone or hearing-aid designs easy.

Artificial Ear
Artificial Ear Type 4153
fulfils the requirements
of IEC 318 and has
an acoustical
impedance basically
similar to that of the
human ear and allows
circum-aural earphones calibration. The acoustic
coupler contains three volumes (V1 = 2.5cm3, V2
= 1.8cm3 and V3 = 7.5cm3) acoustically connected
in parallel by means of a narrow annular slit and
four parallel holes.
The Artificial Ear Type 4153 consist of an acoustic
coupler, a main housing containing the sockets for
the connection of a condenser microphone and a
base plate with a mechanism for clamping the
object being tested. The Artificial Ear is isolated
from shock and vibration by means of three soft
rubber feet.
Artificial Ear Type 4152 has been designed for
measurements in the audiometric and related fields.
The primary function is the calibration of supraaural earphones used in audio-metry in complaince
with IEC 60318-2.
1” Microphone
Type 4144 is a 1″ pressure-field
microphone and the pressure
frequency response is flat over a
wide frequency range. Hence no
correction is needed to the pressure
response below 8 kHz. The use of
pressure-field microphones is recommended where
measurement of the local pressure is of interest, for
instance for coupler measurements. The stability of
Type
4144 combined with its low inherent
noise and high sensitivity makes it
the perfect choice for coupler
measurements.
1/2” Microphone
Type 4192 is a ½″ pressurefield microphone designed for
high-precision coupler
measurements. Being externally
polarized, Type 4192 must be used
with a classical preamplifier. Externally polarized
microphones may be used at higher temperatures
without severe changes in sensitivity.

3

Portable Audiometer Calibration System

Type 9729-W-011

complete with both 6cc
and 2cc coupler, preamplifier, micro-phone,
and adaptor to 1 inch
and ½ inch microphones.
The unique ½ inch
microphone adaptor
design enables very easy
and safe calibration of
the coupler.
Simply
unlock the adaptor and
pull out the ½ inch
microphone, with grid
and preamplifier, and
Calibration set-up for Air Conduction Headset
mount it in Sound
Calibrator Type 4231 or
it is important to calibrate down to any other Brüel & Kjær acoustic
Coupling the earphone
low hearing thresholds, Octave or calibrator. When using a 1”
Acoustic calibration consists of
One-Third Octave Band Filters are microphone, the microphone
measuring the output of the
protection grid must be mounted
used to reject ambient noise
earphones using a standardized
before calibration.
microphone inside a standardized picked up in the coupler. The
It is important to ensure that
coupler called an Artificial Ear. As Artificial Ear Type 4152 comes

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of

4

Type 9729-W-011

the earphone is well coupled to
the sound level meter and that
there are no leaks that would
cause inaccurate sound pressure
level readings. The earphone and
weight should be placed on the
coupler. The audiometer should be
set to produce a continuous signal
at 70 dB HTL at the lowest test
frequency (125 Hz on clinical
audiometers, 250 or 500 Hz on
type 3 or 4 pure-tone airconduction audiometers).
The earphone is then adjusted
on the coupler to produce the
highest sound pressure level
reading on the sound level meter.
Then the earphone and weight are
removed and the process is repeated. The same reading should be
obtained. If so, the earphone
should remain on the coupler for
the rest of its calibration. If not,

Portable Audiometer Calibration System

Calibration set-up for Bone Conduction Headset

the earphone and weight should
be removed and the process
should be repeated until a sound
pressure level reading is

duplicated on successive
placements and adjustments.

fO
n /o
f

5

Portable Audiometer Calibration System

Easy,
flexible,
& reliable
The 9729-W-011
Portable Audiometer
Calibration System:
 reduces typing
errors by avoiding manual data
entering
 reduces the time
needed for audiometer calibration
 prevents errors
caused by incorrect or ignored
corrections for
microphone or
mastoid
The system includes
a professional database for:
 Customers
 Audiometers
 Procedures
 Reports
 House keeping
data
 Instrumentation
 Corrections and
reference values

Start

Audiometer Calibration
in 9 simple Steps...

1

Connect
equipment

Set-up the calibration system by connecting the relevant
components and the instrument to be calibrated into a
measurement chain.

2

Enter
client data

Select client and associated audiometer from database.
If customer does not exist in database enter information including
audiometer and accessery data (type and serialno. etc).

3

Select
procedure

Select calibration test or combination of calibration tests.

4

Enter
atmospheric data

5

Calibrate
system

6

Calibrate
audiometer

7

Adjust
audiometer

8

Recalibrate
audiometer

9

Create
report

Enter temperature, humidity and air pressure - data obtained
from public sources.
Calibrate the measurement chain. Use the reference sound
source and include corrections for microphone and mastoid
obtained from an independent calibration laboratory.
Microphone chain sensitivity correction value is defined and
saved for each calibration.
Calibrate the audiometer. The calibration consists of 3 steps:
1. Calibration - deviations are calculated: the difference between
expected values and measured values.
2. Adjustment - the audiometer is adjusted to meet expected
values.
3. Recalibration, to ensure the correctness of the adjustment.

Use a query to retrieve calibration results from the database and
generate a report using a predefined template.

Finish

Step 1: System Set-up
The 9729-W-011 Portable Audiometer Calibration System comes
in a robust and handy carrying
case containing all instruments,
cables and adaptors needed for
testing and calibrating audiometers—all needed in addition is a PC
and a USB or LAN connection.
The calibration system is setup by connecting the relevant
components and the instrument to
be calibrated into a measurement
chain. The audiometer under test
is connected via LAN or USB
interface.
The set-up is configured according to the options of the system (and optional accessories at
hand) and to the tests to be performed (see figure 2 and 3).

6

Type 9729-W-011

vibrators, microphones, mastoids
and operators are handled by a
SQL database.
It is of major benefit to have all
data stored in a well-defined and
organised form, which facilitates
retrieval, editing and updating. An
additional safety feature is the
regular software notification to
produce a database back-up—in
case of computer failure all data
are preserved.
Prior to starting the actual calibration, the operator must enter
Step 2: Client Data
Data management is a critical part customer information, select calibration procedure and specify the
of the calibration process and a
instruments used. Client and assostrong feature of the calibration
ciated audiometer is selected from
software. Measurement data, rethe database. If the customer
ports, customer data, inventory
does not already exist in the datadata, audiometer data, procedures, corrections for headphones, base, information is entered, inFrom unpacking to reporting a
basic calibration—including system
calibration—only takes 10 minutes.
Step by step the calibration
software guides the operator
through the preparation procedure—all in an intuitive and logical
order. During calibration only the
audiometer is operated by the
calibration technician—the 2250 is
controlled from the software.

Type 9729-W-011

cluding audiometer and accessories data such as type, serialnumber etc.
The acoustic analyzer is recognized by its serial number and
even more importantly by installed software (Active Template). The most frequently used
standardised headphones and vibrators are available in the database as default. Additional equipment can be added by the user
and correction values entered as
required.
Microphone and mastoid calibration corrections can be imported from a USB key or entered
manually. An example of a correction graph is seen in figure 5.
Step 3: Procedure
An audiometer calibration task
incorporates several tests to be
selected depending on the type of
audiometer. All acoustic admittance instruments use a probe
tone that must be calibrated for at
least frequency, SPL and distortion.
The operator can select from a
range of tests:
 Pure tone (Air and Bone conduction level)
 Masking level (Narrow band)
 Masking level (Broad band)
 Attenuator linearity
 Frequency
 Total Harmonic Distortion
(THD)
 Narrow band cut-of frequencies
and bandwidth

Portable Audiometer Calibration System

Figure 3.
The EN-2252 calibration
software guides you
through all steps of the
calibration procedure

Apply calibration level 94.0 dB @ 1000 Hz to the measurement microphone
inside 4152/4153, using BK 4231 acoustic calibrator.

by the user (in reference to standards in question).
Corrections for used transducer
(microphone
and/or mastoid) are
One, more or all supported tests
automatically
read from the datacan be included in the calibration
base
and
taken
into account for
task. Several tests can be merged
into one procedure (e.g. Pure tone calculation of the expected result.
All calculations are performed
first, Insert second and Mastoid
by
the calibration software and
third).
presented
in a table as well as
Each set of tests is usergraphically to provide overview.
defined—the operator can select
During pure tone level calibrathe frequencies at which the tests
tion,
THD and frequency are siare to be executed. All tests are
multaneously
measured and calcompared to limit values defined
culated.

 Rise Time / Fall Time
 Free-field calibration
 Tympanometer calibration

Figure 4.
A new client is added to the database—client data can be reused
for other audiometers or when
next calibration is due

7

Portable Audiometer Calibration System

Type 9729-W-011

Figure 5.
Microphone calibration corrections example
—Brüel & Kjær Type 4144

Step 4: Atmospheric Data
The environmental conditions of the calibration have to
be documented.
The levels of
temperature, air
humidity and air
pressure are entered and will be
included in the
final calibration
report. These
data can be obtained from public sources.
Figure 6.
Audiometer calibration in progress
- coloured dots indicate measurement status

8

Step 5: System
Calibration
Traceability of

measurement results is an integral
part of the calibration procedure.
Traceability is obtained by measurement chain calibration at the
beginning of each audiometer calibration. Type 4231 is used as the
reference sound source producing
94dB at 1kHz—the software automatically includes corrections for
microphone and mastoid obtained
from an independent calibration
laboratory. The microphone chain
sensitivity correction value is defined and saved for each completed calibration. The EN-2252
Software constantly monitors the
validity of calibration equipment in
use.
Calibration can start as soon as
these conditions for correct calibration documentation are fulfilled.

Type 9729-W-011

Steps 6, 7 & 8:
Calibration
When all relevant data are in
the database, it
is only a matter
of selecting the
calibration
equipment and
the audiometer
to be tested,
and calibration
is started.
The calibration of an audiometer is performed in three
steps:
1. Calibration deviations
are calculated: the
difference
between expected values and measured
values.
2. Adjustment - the audiometer is
adjusted to meet expected values.
3. Recalibration - the audiometer
is calibrated once more to ensure the correctness of the adjustment.
Online guidance eases the calibration and prevents the operator
from missing important steps or
taking incorrect actions. Each time
the operator needs to intervene
while calibration is in progress, a
window with clear and instructive
information will appear.
Any deviation exceeding limit
value displays an information window with the options to repeat or
accept the result. Results which
are out of tolerance limits get red
light in front of the step in question. During semiautomatic calibration, only the audiometer is
operated by calibration technician.
Intervention with Type 2250 is not
needed at all—it is controlled from
the software.
The calibration software constantly monitors the calibration
validity of client audiometers and
automatically sends out a notice
on expired calibrations at start-up
or on request.

Portable Audiometer Calibration System

Figure 7.
Audiometer adjustment
instructions

creating report or just to be
viewed on the screen. A query
function provides capability to retrieve only the calibrations fulfilling specific criteria.

Selected calibrations can be
examined on the screen or sent to
Excel or Word using either a predefined or customer defined reporting template.
Figure 8.
Reporting example
—part of calibration
certificate

Step 9: Reporting
Calibration results are saved in
the database and available for

9

Portable Audiometer Calibration System

Type 9729-W-011

fO n /o f

dB
fOn

/Of

10

+20

Free Field calibration
Pure tone audiometry deliver and important
information related to the loss of human ear
sensitivity. It is a good indicator for the candidates
for hearing aid.
However, practice has proven that just
increasing the hearing sensitivity is far from
satisfactory as the reasons for hearing impairment
can lie in different sections of the hearing chain.
Therefore it is necessary to conduct another test
which reveal not only what sound a person can
detect, but more important how much this person
can actually understand—a speech audiometric
test.
When speech audiometry is conducted in a test
room or booth using loudspeakers exact conditions
for the test must be provided. It is important to
check and calibrate the sound level at the
reference point (the point where the head of the
test person is), check and calibrate the
homogeneity of the sound field around reference
point, measure THD, linearity and frequency
response of the audio system.
The loudspeaker should be head-height of the
seated listener, and directed towards the reference
point. In absence of the test subject the sound
pressure levels 0.15 m above, below and to the left
and right of the reference point should not vary by
more than 1 dB from those predicted by the
inverse square law.
Mesurements for free or quasi-free sound fields
are specified by ISO 8253-2. The standard
describes the characteristics of free-field and
diffuse field characteristics and the procedures and
conditions of use for sound field audiometry.

Figure 9.
System set-up for free-field
audiometer calibration or audiometric test room /
booth verification.

Tympanometers - Impedance audiometers
Impedance is measured by using a probe to
present a sound of 226 Hz. into a cavity like the
human ear. This produces different SPLs depending
on the volume of the cavity of the ear. By measuring the SPL, the equivalent volume can be
established, and by tracking the changes in SPL,
the equivalent changes in the cavity can be
identified
The tympanometer should be tested regularly as
the probe is very fragile and possible impact on the
transducer will affect measurements. The complete
system has to be calibrated at least once a year.
The calibration is divided into two parts:
1. The instrument itself, which includes the air
system
2. The software, which involves adjustments of
different parameters via soft keys.
The EN-2252 software guides the operator through
the specific tympanometer calibration process:
probe calibration, compliance and reflex,
manometer and Ipsilateral Pure Tone level. The
calibration also includes the parameters that apply
for Pure Tone Audiometers (linearity, frequency,
THD etc).
The technical requirements for tympanometers
are specified in IEC 60645-5 and for the acoustic
part in IEC 60645-1. Calibration and test
procedures are specified in IEC 1027 and ANSI
S3.39 - 1987.

Type 9729-W-011

Standards:
EN-2252 Audiometer Calibration Software and
Sound Analyzer Type 2250 conforms with the
relevant parts of the following standards:
 IEC 60645-1:2001 Electroacoustics - Audiological
equipment - Part 1: Pure-tone audiometers
 ANSI/ASA S3.6-2010 Specification for
Audiometers
 ISO 389 Acoustics - Reference zero for the
calibration of audiometric equipment
 IEC 60318-3 1998 Electroacoustics - Audiological
equipment - Acoustic coupler for the calibration
of supra-aural earphones used in audiometry
 ANSI S3.39-1987 (R 2007) Specifications for
Instruments to Measure Aural Acoustic
Impedance and Admittance (Aural Acoustic
Immittance)
Calibration and test procedures are specified in:

 ISO 8253-1:2010 Acoustics - Audiometric test

methods - Part 1: Pure-tone air and bone
conduction audiometry
 ISO 8253-2:2009 Acoustics - Audiometric test
methods - Part 2: Sound field audiometry with
pure-tone and narrow-band test signals
 ISO 8253-3:1996 Acoustics - Audiometric test
methods - Part 3: Speech audiometry

Portable Audiometer Calibration System

 IEC 60645-5:2004 Audiometric equipment - Part
5: Instruments for the measurement of aural
acoustic impedance/admittance.
 ANSI/ASA S3.7-1995 (R 2008) Method for
Coupler Calibration of Earphones

Calibration options:
The calibration options available with this Portable
Audiomter Calibration System based on Brüel &
Kjær Types 2250 or 2270 can cover:
 Pure tone (Air and Bone conduction level)
 Masking level - Narrow band (BZ-7230)
 Masking level - Broad band
 Attenuator linearity
 Frequency (BZ-7230)
 Total Harmonic Distortion (BZ-7230)
 Narrow band cut-of frequencies and bandwidth
(BZ-7230)
 Rise Time / Fall Time
 Free-field calibration (BZ-7230)
 Tympanometer calibration (Manometer required)

ORDERING INFORMATION
9729-W-011 Calibration System
using Supra-aural Earphones
 2250-B - Hand Held Analyzer with Sound Level
Meter and Frequency Analysis Software
 4153 - Artificial Ear / Ear Simulator (IEC 60 318
coupler without microphone & preamplifier)
 4192 - 1/2" Pressure-field Microphone, 3Hz to
20KHz, 200V Polarization
 AO-0645-D-100 - Cable, Microphone, circular-1B
7-pin (F) to circular-1B 10-pin (M), 10m
(33.3ft),max.+90°C (194°F)
 4231 - Sound Calibrator Class 1 and LS, 94 and
114 dB, 1 kHz
 BK-XXXX - Suitcase/transportation case
 EN-2252 - Audiometer Calibration Software
 4946-Q-002 - 2CC Click-on Coupler for QC w/o
microphone and preamplifier
 DB-3869 Ear Plug Simulator with Tube Stud for
BTEs

9729-W-012 (9729-W-011 Calibration System
with add-ons for Bone Vibrators)
 4930 - Artificial Mastoid
 JJ-2617 - Input adaptor,1/2" microphone to
microdot
 BZ-7230 - FFT Analysis Software
 AO-0038-D-005 - Cable super low-noise,10-32
UNF (M) to 10-32 UNF (M),0,5m
(1,7ft),max.+250°C (482°F)
Optional
 4152 - Artificial Ear / Ear Simulator (6cc coupler
without microphone & preamplifier)
 4144 - 1" Pressure- field Microphone, 3Hz to
10KH,200V Polarization
 Pressure meter
 Tube kit
 4955 - ½” Low Noise Microphone system 5Hz to
20kHz, External Polarized
 ZE-0948 - USB Audio Interface

11

Portable Audiometer
Calibration System

Type 9729-W-011

Benefits:






Truly portable—easy to carry
Easy to use—no special skills required
Automated calibration and reporting
On-line calibration instructions
Automated correction of all instruments

SOUND AND VIBRATION
- CONTACT BRÜEL & KJÆR






Traceable measurements and validity
monitoring
Easy data-handling—storage and retrieval
Compliance to standards IEC 60645, 389
and 8253
Full flexibility for professional use

Please, contact your local
Brüel & Kjær representative for more information:

Brüel & Kjær
Sound & Vibration Measurement A/S
Export Sales
Skodsborgvej 307
DK-2850 Nærum, Denmark
Phone: +45 7741 2000
Fax: +45 7741 2015
E-mail: export@bksv.com
www.bksv.com
HEADQUARTERS: Brüel & Kjær Sound & Vibration Measurement A/S • DK-2850 Nærum • Denmark
Telephone: +45 7741 2000 • Fax: +45 4580 1405 • www.bksv.com • info@bksv.com
Local representatives and service organisations worldwide

EXPORT SALES, MARCH 2012

This product is for sale in Eastern and Central
Europe, the Middle East and Africa.
For countries in other regions contact the
local Brüel & Kjær office.



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