Bruel & kjaer 4128 Operation manual

Product Data

Brüel & Kjær

Head and Torso Simulator — Type 4128

Head and Torso Simulator Type

4128 has been developed for objective

in-situ research and evaluation of:

❍telephones and headsets

❍audioconference devices

❍microphones

❍headphones

❍hearing aids and hearing protectors

The design of Type 4128 is based on

an efficient minimum-parameter de-

scription of the median human adult.

It provides a correct representation of

the acoustic field around a human

head and torso.

The acoustic performance and the

main physical dimensions of Head and

Torso Simulator Type 4128 conform to

the requirements of ITU-T Rec.P.58,

IEC959, and ANSI S 3.36–1985.

The built-in mouth simulator closely

replicates the sound field generated by

the human mouth, including the fre-

quency-dependent motion of the acous-

tic centre in the frequency range which

is important for noise-cancelling micro-

phones.

USES:

❍Measurements on handset and headset telephones

❍Measurements on loudspeaking and hands-free

telephones for mobile and domestic use

❍In-situ/insertion measurements of hearing aids

❍Evaluation of headphones

❍Evaluation of hearing protectors

❍Evaluation of close-talking/noise-cancelling

microphones

FEATURES:

❍Manikin with surfaces replicating the shape of a

median adult human head and torso

❍Highly-representative mouth simulator with overload

protection

❍Highly-representative IEC711/ITU-T Type 3.3

based calibrated ear simulator (Type 4158) with

built-in 1/2" condenser microphone and microphone

preamplifier

❍Compliance with the acoustic requirements of

ITU-T Rec.P.58, IEC959, and ANSI S3, 36–1985

❍Soft Pinnas included for realistic headphone

measurements

Introduction

Head and Torso Simulator Type 4128

consists of a head mounted on a torso

which extends to the waist. You can

use it free-standing, or fitted on a

tripod or rotating table using the tri-

pod mounting-adaptor supplied.

With its simplified shape, Type

4128 has the international average

dimensions of a human adult. In air-

borne acoustic measurements it pro-

vides the correct simulation of the

acoustic field around a human head

and torso.

The Mouth Simulator

The mouth simulator in the Head

and Torso Simulator (see Fig.1) has

a high-compliance loudspeaker which

gives powerful low-frequency re-

sponse and low distortion. The acous-

tic transmission path from the

loudspeaker to the mouth opening

ensures an easily-equalizable fre-

quency response of the sound pres-

sure level in front of the mouth. The

equivalent lip plane is 6mm in front

of the mouth opening. The usual cal-

ibration position is at the ITU-T

Mouth Reference Point (MRP), 25mm

in front of this plane. A holder is sup-

plied with the 4128 which will hold

a reference microphone (Brüel&Kjær

Type 4135 with Preamplifier Type

2633) at precisely the correct dis-

tance for calibration at the MRP. This

holder can also hold a microphone

right at the opening of the mouth if

you want to monitor the sound pres-

sure at this point.

The mouth simulator produces a

sound-pressure distribution around

the opening of the mouth which sim-

ulates that of a median adult human

mouth, correlating to the figures giv-

en in ITU-T Recommendation P.51.

The position of the acoustic-centre of

the mouth simulator also follows that

of human subjects over the speech

frequency range.

Ear Simulator Type 4158

Ear Simulator Type 4158, is shown

in Fig.2. It consists of a removable

silicone-rubber pinna joined to an ear

canal. The pinna complies with ITU-

T Rec. P57. The ear canal ends in an

occluded ear-simulator which simu-

lates the inner part of the ear canal

according to the ICE711 standard

The occluded ear-simulator contains

a 1/2” microphone and is through an

adaptor connected to a microphone

preamplifier.

Type 4158 is the right ear of Type

4128. A left ear, Type 4159, is also

available for measurements requir-

ing two ears. For headphone meas-

urements soft pinnas are also

available (refer to the section about

this subject). Both Type 4158 and

Type 4159 are delivered with a cali-

bration chart specific to their ear sim-

ulator and pinna.

Suitable calibration reference lev-

els can be generated by Pistonphone

Type 4228 or Sound Level Calibrator

Type 4231.

The combined influence of the tor-

so, head, pinna and ear-canal on air-

borne sound signals can be quantified

by the acoustic free-field transfer

function (the frequency response

from free-field to the eardrum). This

is called the listener frequency re-

sponse in telecommunications work

and the manikin frequency response

in technical audiology. The response

of Type 4128 for sound incident at 0°

(that is, coming from the front) is

shown in Fig.3. The listener diffuse-

field frequency response is also

shown.

Type 4128 has an adjustable neck al-

lowing you to position the head in a

realistic posture for different posi-

tions of the torso. This is useful in

real-life simulations, for example

measurements in car seats. To update

earlier versions of Type 4128 with no

neck ring, a Torso with neckring

(UC5345) is available as an accesso-

ry.

Applications

Telephone Measurement

The Head and Torso Simulator Type

4128 can be used as a representative

manikin for the in-situ evaluation of

telephone equipment (see Fig.4), in-

cluding handset telephones, hands-

free telephones, group audio termi-

nals and group audio headsets. With

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Protection

Circuit Loudspeaker

Mouth

Adaptor

6 mm

Equivalent

Lip-plane

951069/1e

Pinna

Microphone

Preamplifier

Occluded

Ear Simulator Adaptor

Fig. 2 Cross-section of the pinna of the right ear with the ear

simulator fitted

Fig.1 The mouth simulator of Type 4128

both an ear- and a mouth-simulator

you can investigate receive, transmit,

acoustic sidetone and background

noise characteristics for the full

range of audio terminal devices. Full

duplex operation is possible.

Brüel & Kjær Audio Analyzer Type

2012 is ideal for telephone measure-

ments because it has post-processing

facilities which allow for the calcula-

tion of quantities such as Loudness

Rating in the analyzer itself (with

Special Calculation Software Type

7661). You can also make simulated

free-field measurements in ordinary

rooms.

Type 4128 is especially useful for

developing new designs of telephone

equipment. Realistic simulation of

the acoustic leakage between a hand-

set and the human pinna enables

measurements of low impedance de-

vices to be performed. In addition,

Type 4128 accurately simulates the

“obstacle effect” of the head, allowing

realistic measurements on loud-

speaking or hands-free telephones to

be made.

Headphone Characteristics

You can use Type 4128 to determine

a variety of headphone characteris-

tics in-situ. Any type of headphone

can be investigated; the influence of

the pinna is taken into account and

the ear simulator provides the correct

acoustic loading, so realistic evalua-

tion of open, closed and insert head-

phones can be made. For insert

headphone or earphone measure-

ments an additional set of non-cali-

brated pinnas (left and right) with a

hardness very close to that of a real

human pinna are supplied with the

4128. These soft pinnas feature a

Shore A hardness of more than 4

times less the standard Type 3.3 pin-

na. This enables an easy and realistic

mounting of any type of headphone.

Simulated insertion responses are

measured referring to either the

equivalent free-field, or diffuse-field

response. Moreover, when used with

Audio Analyzer Type 2012, frequency

response measurements are made

simply and rapidly.

Type 4128 can also be used to de-

termine the left/right tracking of

headphones and their background

noise insertion-loss.

Hearing Protector Evaluation

Evaluating hearing protectors is

straightforward and much more reli-

able using the Head and Torso Sim-

ulator instead of human subjects. The

most important characteristic for

hearing protectors is airborne inser-

tion loss; this is found by measuring

the free-field transfer function of the

Type 4128 fitted with a hearing pro-

tector and then giving this result rel-

ative to the free-field response of the

4128. Diffuse-field measurements

can be used instead of free-field if

they are more relevant to the envi-

ronment in which the hearing protec-

tors are going to be used. Audio

Analyzer Type 2012 is able to per-

form the measurements and post-

processing necessary without the

need for an external computer.

The Type 4128 can be placed in-

situ so the actual noise sources for

which the hearing protector is de-

signed can be used in tests. The ef-

Fig.3 The listener free-field frequency response and the diffuse-field frequency response

of Type 4128

880830e

Free-field

Diffuse-field

125 250 500 1k 2k 4k 8k A L

–10

–5

[Hz]

20.0dB re 20.0µPa

TEST

1W Spectrum REREF

RMS

Fig.4 Measurement of telephone headset using Type 4128, Audio Analyzer Type 2012

and Telephone Interface Type 5906/WH2517

930115e

Audio Analyzer

2012

Head and Torso

Simulator

4128

Brüel

7/6-'89

&Kjær

Head and Torso Simulator

Type 4128

Telephone Interface

5906/WH 2517

To Mouth

Simulator

Dir.

Preamp

IEEE-488

Bus

From Separate

Output. f1

From Common

Output

fectiveness of hearing protectors on

noise incident at different angles is

also easy to investigate.

Hearing Aid Characteristics

Both in-the-ear and behind-the-ear

hearing aids can be evaluated with

Type 4128. Two ear-mould simulators

are supplied with the 4128 for testing

hearing aids where individually-

made ear-moulds are normally used.

The mouth simulator in Type 4128 is

very useful for developing multi-mi-

crophone noise-cancelling hearing

aids.

Simulated insertion gain, simulat-

ed directional responses and in-situ

maximum output can be measured

using the Head and Torso Simulator,

as described in IEC Publication

118–8 (1983) Methods of Measure-

ment of Performance Characteristics

of Hearing Aids under Simulated In-

situ Working Conditions.

Microphone Measurement

When making measurements on mi-

crophones, Type 4128 can closely sim-

ulate the interaction between the

mouth, head, body and microphone.

Its mouth simulator is an ideal sound

source for applications in research,

development and evaluation of a va-

riety of microphones. In particular,

you should use the 4128 with close-

talking, noise-cancelling and lavalier

types, where the characteristics of

the human voice must be reproduced

accurately and the influence of the

head and body is very important.

Speech Intelligibility Investigation

You can investigate the quality of

speech intelligibility in a room using

the Head and Torso Simulator, to-

gether with the Brüel & Kjær Speech

Transmission Meter Type 3361. This

quantifies speech intelligibility based

on the RASTI (RApid Speech Trans-

mission Index) method. Type 4128 is

incorporated in the system as trans-

mitter, simulating the speaker, and

can be driven from the transmitter

part of the system. The RASTI calcu-

lation is performed by the receiving

part of the 3361.

LISTENER FREQUENCY RESPONSE:

Conforms to ITU-T Rec.P.58 for measurements

on telecommunications devices and to IEC959

and ANSI S3.36-1985 for measurements on air

conduction hearing aids

EAR SIMULATOR:

The output from the ear simulator is via a built-

in 7-core 3m cable (2.3m from the bottom of the

torso) terminated with a standard plug for con-

nection to a preamplifier input socket of

Brüel&Kjær Power Supplies, Analyzers, etc. The

Ear Simulator complies with IEC711 and

ANSIS3.25 standards

Sensitivity: 9mV/Pa(–41dB re 1V/Pa) at 250Hz

3% distortion level:160dB re 20µPa at ear-

drum position

LEFT-EAR TO RIGHT-EAR TRACKING:

±1dB up to 5kHz, ±3dB up to 8kHz (measured

using the same Ear Simulator)

PINNA SIMULATORS:

Dimensions similar to those specified in ITU-T

Rec.P.58, IEC959 and ANSIS3.36-1985. Minor

adjustments in the dimensional details have

been made which enable the 4128 to conform

with the acoustic specifications of these docu-

ments in the frequency range 100Hz to 8kHz.

Types 4158 and 4159 are supplied with calibrat-

ed pinna simulators. An additional pair of uncal-

ibrated soft pinna simulators are supplied with

the 4128

MOUTH SIMULATOR:

Input to mouth simulator via 0.75m cables (0.2m

from the bottom of the torso) terminated with

banana-sockets

Sound pressure distribution conforms to: ITU-T

Mouth opening:W×H: 30×11mm

(42×16mm with mouth adaptor removed)

Equivalent lip plane position:6mm in front of

the sound radiation opening

Continuous output level at MRP:

Min. 110dB SPL, 200Hz to 2 kHz

Min. 100dB SPL, 100Hz to 8kHz

Distortion (harmonic components up to

8kHz) at 94dB SPL:

<2%, 200Hz to 250

<1% >250Hz

Max. average input power:10W max. continu-

ous average power (at 20°C (68°F))

Max. pulsed input power:50W for 2 seconds

(limited by protection circuit)

Loudspeaker impedance:4Ω

Loudspeaker diameter:80mm (3.1in)

(all mouth-simulator performance parameters

are measured at 25mm from the equivalent lip

plane (ITU-T MRP))

DIMENSIONS:

The main dimensions comply with the dimen-

sional requirements of ITU-T Rec.P.58 and the

reports from IEC959 and ANSIS3.36-1985

Total height, head and torso:695mm (27.4in)

Torso: Height:460mm (18in)

Width:410mm (16in)

Depth:183mm (7.2in)

External neck diameter: 112mm

(4.4in)

Head Angles: Vertical or 17°

WEIGHT: 9kg (20lb)

COMPLIANCE WITH STANDARDS:

CE-mark indicates compliance with: EMC Directive and Low Voltage Directive.

Safety EN 61010–1 (1993): Safety requirements for electrical equipment for

measurement, control and laboratory use.

EMC Emission EN 50081–1 (1992): Generic emission standard. Part 1: Residential,

commercial and light industry.

CISPR22 (1993): Limits and methods of radio disturbance characteristics of

information technology equipment. Class B Limits.

FCC Class B limits.

EMC Immunity EN 50082–1 (1992): Generic immunity standard. Part 1: Residential,

commercial and light industry.

Note: The above is guaranteed using accessories listed in this Product Data

sheet only.

Temperature IEC68–2–1 & IEC68–2–2: Environmental Testing. Cold and Dry Heat.

Operating Temperature: –5°C to +40°C

Storage Temperature: –25°C to +70°C

Humidity IEC68–2–3: 90% RH (non-condensing at 40°C)

Mechanical IEC68–2–6: Vibration: 0.3mm, 20m/s2, 10–500Hz

IEC68–2–27: Shock: 1000m/s2

IEC68–2–29: Bump: 1000 bumps at 250m/s2

Specifications 4128

Ordering Information

Type 4128 Head and Torso Simulator

Including:

Type 4158 Right Ear Simulator

Mouth Simulator

and the following accessories:

BC5000 Calibration Disk

BC0183 Calibration Chart – Listener

Frequency

BC0181 Calibration Chart – Talker

Fequency

BC0188 Calibration Chart – Type 4158

DZ9751 Left Pinna – soft

DZ9752 Right Pinna – soft

DB2902 Ear Mould Simulator

UC0199 Ear Mould Simulator – long

UA1034 Adaptor for Calibration

QA0167 Ear Mounting Tool

UC5290 Adaptor for Tripod

QA0038 Allen Key

UA1052 Handle

UA1043 Pair of Feet

Optional Accessories

Type 4159 Left Ear Simulator

UC5345 Torso with adjustable neck ring

DZ9626 Left Pinna

DZ9627 Right Pinna

AO0027 Microphone Extension Cable 3m

AO0028 Microphone Extension Cable 10m

AO0029 Microphone Extension Cable 30m

UA0587 Tripod

Brüel&Kjær reserves the right to change specifications and accessories without notice

Brüel & Kjær

BP0521–17 96/09

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