Portable Audiometer Calibration System March 2012 BRK_4135 BRK 4135

User Manual: BRK_4135

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The Type 9729-W-011 Portable

Audiometer Calibration System is

an easy, flexible and reliable solu-

tion for automated calibration of

audiometers to IEC and ANSI

standards.

The system performs the tasks

ranging from basic standard audi-

ometer testing with fully auto-

mated 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 calibra-

tion and metrology laboratories.

Other fields of use are audiometer

research & development and fac-

tory 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 cali-

bration 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.

The calibration system is not

limited to any specific brand or

type of audiometer, but can cali-

brate any audiometer that com-

plies 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 in-

house calibration services or pro-

duction tests as well as for use in

the field, without compromising

neither accuracy nor stability.

Portable Audiometer

Calibration System

Type 9729-W-011

PRODUCT DATA

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)

Features

 Calibration procedures based on international

standards for air conductive and bone conductive

transducers.

 Multiple test procedures.

 Semi- or fully automated procedures execution.

 Automatic correction for microphone and artificial

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 pa-

rameters.

 Tracking of calibration equipment inventory and

calibration date.

 Audiometer adjustment instructions

 Customized calibration reports

 Calibration reminder via e-mail.

USES AND FEATURES

… Easy, flexible

and reliable

On/off

Audiometer Calibration

The purpose of any calibration

measurement is to check that the

measurement equipment is meas-

uring correctly. Regular testing

and calibration of an audiometer is

required to maintain maximum

measurement accuracy.

For absolute acoustic calibra-

tion 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 measure-

ments are fundamental to charac-

terise and quantify hearing loss,

and consequently for selection of

hearing aids and for general

health and safety monitoring.

Prober calibration ensures that the

measurements are consistent, no

matter where the they are carried

out.

The system calibrates audio-

meters using an ear simulator

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.

Type 9729-W-011

Portable Audiometer Calibration System

Calibration..?

2

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 transdu-

cers:

1. Ear phones

2. Bone vibrator

3. Loud speaker (free-field)

Output transducers for audio-

meters cannot be replaced or

changed without calibrating

the whole equipment.

Calibration of the audiome-

ter involves calibration of the

audiometer proper, of ear pho-

nes, 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 2.

Set-up of 9729-W-011

Portable Audiometer

Calibration System

Figure 1.

Main menu of the EN-2252 software

—a simple and intuitive user interface with all functionalities

Type 9729-W-011 Portable Audiometer Calibration System

3

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 hand-

held 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 Ear Type 4152 has been designed for

measurements in the audiometric and related fields.

The primary function is the calibration of supra-

aural 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.

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.

System Instrumentation

The calibration system is based on Hand-held Acoustic Analyzer Type 2250 and the

Audiometer Calibration Software Type EN-XXXX.

1/2” Microphone

Type 4192 is a ½″ pressure-

field 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.

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.

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.

Coupling the earphone

Acoustic calibration consists of

measuring the output of the

earphones using a standardized

microphone inside a standardized

coupler called an Artificial Ear. As

it is important to calibrate down to

low hearing thresholds, Octave or

One-Third Octave Band Filters are

used to reject ambient noise

picked up in the coupler. The

Artificial Ear Type 4152 comes

complete with both 6cc

and 2cc coupler, pre-

amplifier, 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

mount it in Sound

Calibrator Type 4231 or

any other Brüel & Kjær acoustic

calibrator. When using a 1”

microphone, the microphone

protection grid must be mounted

before calibration.

It is important to ensure that

On/of

f

Portable Audiometer Calibration System Type 9729-W-011

4

Calibration set-up for Air Conduction Headset

On/of

f

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 airconduc-

tion 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 repea-

ted. The same reading should be

obtained. If so, the earphone

should remain on the coupler for

the rest of its calibration. If not,

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.

Type 9729-W-011 Portable Audiometer Calibration System

5

Calibration set-up for Bone Conduction Headset

Step 1: System Set-up

The 9729-W-011 Portable Audi-

ometer Calibration System comes

in a robust and handy carrying

case containing all instruments,

cables and adaptors needed for

testing and calibrating audiome-

ters—all needed in addition is a PC

and a USB or LAN connection.

The calibration system is set-

up 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 ac-

cording to the options of the sys-

tem (and optional accessories at

hand) and to the tests to be per-

formed (see figure 2 and 3).

From unpacking to reporting a

basic calibration—including system

calibration—only takes 10 min-

utes.

Step by step the calibration

software guides the operator

through the preparation proce-

dure—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.

Step 2: Client Data

Data management is a critical part

of the calibration process and a

strong feature of the calibration

software. Measurement data, re-

ports, customer data, inventory

data, audiometer data, proce-

dures, corrections for headphones,

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 cali-

bration, the operator must enter

customer information, select cali-

bration procedure and specify the

instruments used. Client and asso-

ciated audiometer is selected from

the database. If the customer

does not already exist in the data-

base, information is entered, in-

6

Portable Audiometer Calibration System Type 9729-W-011

Easy,

flexible,

& reliable

The 9729-W-011

Portable Audiometer

Calibration System:

 reduces typing

errors by avoi-

ding manual data

entering

 reduces the time

needed for audio-

meter calibration

 prevents errors

caused by incor-

rect or ignored

corrections for

microphone or

mastoid

The system includes

a professional data-

base for:

 Customers

 Audiometers

 Procedures

 Reports

 House keeping

data

 Instrumentation

 Corrections and

reference values

Set-up the calibration system by connecting the relevant

components and the instrument to be calibrated into a

measurement chain.

Audiometer Calibration

in 9 simple Steps...

Start

Finish

Connect

equipment

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).

Select calibration test or combination of calibration tests.

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.

Calibrate

audiometer

Adjust

audiometer

Recalibrate

audiometer

1

Enter

client data

Select

procedure

Enter

atmospheric data

Calibrate

system

Create

report

9

6

5

4

3

2

7

8

cluding audiometer and accesso-

ries data such as type, serial-

number etc.

The acoustic analyzer is recog-

nized by its serial number and

even more importantly by in-

stalled software (Active Tem-

plate). The most frequently used

standardised headphones and vi-

brators are available in the data-

base as default. Additional equip-

ment can be added by the user

and correction values entered as

required.

Microphone and mastoid cali-

bration corrections can be im-

ported from a USB key or entered

manually. An example of a correc-

tion 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 admit-

tance instruments use a probe

tone that must be calibrated for at

least frequency, SPL and distor-

tion.

The operator can select from a

range of tests:

 Pure tone (Air and Bone con-

duction level)

 Masking level (Narrow band)

 Masking level (Broad band)

 Attenuator linearity

 Frequency

 Total Harmonic Distortion

(THD)

 Narrow band cut-of frequencies

and bandwidth

 Rise Time / Fall Time

 Free-field calibration

 Tympanometer calibration

One, more or all supported tests

can be included in the calibration

task. Several tests can be merged

into one procedure (e.g. Pure tone

first, Insert second and Mastoid

third).

Each set of tests is user-

defined—the operator can select

the frequencies at which the tests

are to be executed. All tests are

compared to limit values defined

by the user (in reference to stan-

dards in question).

Corrections for used transducer

(microphone and/or mastoid) are

automatically read from the data-

base and taken into account for

calculation of the expected result.

All calculations are performed

by the calibration software and

presented in a table as well as

graphically to provide overview.

During pure tone level calibra-

tion, THD and frequency are si-

multaneously measured and cal-

culated.

Type 9729-W-011 Portable Audiometer Calibration System

7

Figure 4.

A new client is added to the data-

base—client data can be reused

for other audiometers or when

next calibration is due

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.

8

Portable Audiometer Calibration System Type 9729-W-011

Step 4: Atmos-

pheric Data

The environ-

mental condi-

tions of the cali-

bration have to

be documented.

The levels of

temperature, air

humidity and air

pressure are en-

tered and will be

included in the

final calibration

report. These

data can be ob-

tained from pub-

lic sources.

Step 5: System

Calibration

Traceability of

measurement results is an integral

part of the calibration procedure.

Traceability is obtained by meas-

urement chain calibration at the

beginning of each audiometer cali-

bration. Type 4231 is used as the

reference sound source producing

94dB at 1kHz—the software auto-

matically includes corrections for

microphone and mastoid obtained

from an independent calibration

laboratory. The microphone chain

sensitivity correction value is de-

fined and saved for each com-

pleted calibration. The EN-2252

Software constantly monitors the

validity of calibration equipment in

use.

Calibration can start as soon as

these conditions for correct cali-

bration documentation are ful-

filled.

Figure 5.

Microphone calibration corrections example

—Brüel & Kjær Type 4144

Figure 6.

Audiometer calibration in progress

- coloured dots indicate measurement status

9

Type 9729-W-011 Portable Audiometer Calibration System

Steps 6, 7 & 8:

Calibration

When all rele-

vant 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 calibra-

tion of an audi-

ometer is per-

formed in three

steps:

1. Calibration -

deviations

are calcu-

lated: the

difference

between ex-

pected values and measured

values.

2. Adjustment - the audiometer is

adjusted to meet expected val-

ues.

3. Recalibration - the audiometer

is calibrated once more to en-

sure the correctness of the ad-

justment.

Online guidance eases the calibra-

tion 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 win-

dow 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 ques-

tion. During semiautomatic cali-

bration, 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 con-

stantly monitors the calibration

validity of client audiometers and

automatically sends out a notice

on expired calibrations at start-up

or on request.

Step 9: Reporting

Calibration results are saved in

the database and available for

creating report or just to be

viewed on the screen. A query

function provides capability to re-

trieve only the calibrations fulfill-

ing specific criteria.

Selected calibrations can be

examined on the screen or sent to

Excel or Word using either a pre-

defined or customer defined re-

porting template.

Figure 7.

Audiometer adjustment

instructions

Figure 8.

Reporting example

—part of calibration

certificate

Portable Audiometer Calibration System Type 9729-W-011

10

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.

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 measu-

ring 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.

Figure 9.

System set-up for free-field

audiometer calibration or audiometric test room /

booth verification.

On/off

+20dBOn/Of

f

Type 9729-W-011 Portable Audiometer Calibration System

11

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

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

 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)

Please, contact your local

Brüel & Kjær representative for more information:

EXPORT SALES, MARCH 2012

SOUND AND VIBRATION

- CONTACT BRÜEL & KJÆR

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.

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

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

 Traceable measurements and validity

monitoring

 Easy data-handling—storage and retrieval

 Compliance to standards IEC 60645, 389

and 8253

 Full flexibility for professional use

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