Bruel & kjaer 2225 User manual

Instruction

Manual

Integrating Sound Level

Meter

Type

2225

Integrating Impulse Sound Level

Meter

Type

2226

1-~-~-1

-=e

·-=

-

--

: e

·-=

0..

-

or;

-

-}-

-

·-=

-

..;

Briiel•l(

j

ar

~

Type

22211

033-0523

Two

portable Sound Level

Meters

with

easy-

to-read

"thermometer"

display, complying

with

IEC

651

Type

2*,

DIN

45634

and

ANSI

S1

.4 -

1971

Type

S2A.

An

A-weight-

ing

network

is

built-in.

"Fast"

and

"Slow"

time

constants

and a one

minute

L

eq

easily

converted

to

SEL

(LAx)

on both meters. In

addition

the

2225

has a

"Peak"

hold and

the

2226

an

"Impulse"

function

and

"Max.

hold"

facility

on all

time

constants. The

measuring

range

from

25

dB(A)

to

1

40

dB(A) peak is covered in 4 overlapping

40

dB(A) ranges.

Automatic

reset and

other

features

enable operators

to

make accurate

valid

measurements

after

a

short

period

of

familiarisation.

DC

output

to

a level recor-

der.

Supplied

with

Prepolarised Condenser

Mic-

rophone Type

4175

• except for

"Max

.

hold"

on

2225

+

BrUel

&

Kjaer

INTEGRATING

SOUND

LEVEL

METER

TYPE

2225

AND

INTEGRATING

IMPULSE

SOUND

LEVEL

METER

TYPE

2226

Applicable

to

instruments

from

Serial No.

796650

October

1979

CONTENTS

1.

INTRODUCTION

AND

SPECIFICATIONS

(PRODUCT

DATA)

.................................................

1

2.

CONTROLS

..................................................................................................................

·

·.

····· 5

3.

OPERATION

.........................................................................................................................

8

3.1 . INTRODUCTION

............

....

...............

.

...........................

.

..........

..

..............

8

General

Considerations

............................................................................ 8

3.2.

BATIERY

INSTALLATION

............................................................

....

..

.....

..

8

3.3.

MOUNTING THE MICROPHONE ....

............................

.. .. ..

..........

.. ..

....

........

9

3.4

. CALIBRATION

.........

.

..........................

.

........................

..

......

.....

............... 9

3.5

. SOUND LEVEL MEASUREMENTS

.....

.

............

......

..

.

..

................

.:

.............

10

General

.....

....

................

......

.

.........

........

..................................

.....

10

Procedure

for

Sound

Level

Measurement

...................................................

11

Noise Dose

Measurements

....................................................................... 12

SEL(LAx)

Measurement

........................................................................... 12

4.

USE

WITH

OTHER

INSTRUMENTS

......................................................................................

13

4. 1.

DC

LEVEL RECORDING ............................................................................ 13

Robustly

constructed

in a compact

case,

the

types

2225

and

2226

are

go

-

anywhere

instruments

.

Light

in

weight,

but

full

of

facilities

for·

easy

comprehensive

A-

weighted

measure-

ment

of

commun

i

ty

or .

industrial

noise.

The

short

-

term

(60

second)

leq

meas

-

urement,

used on

fluctuating

signals,

eliminates

the

errors

inherent

in

aver-

aging by eye and can also be used

to

obtain

SEL(LAX ).

"Slow

" , "

Fast"

and

"

Peak"

hold

(with

a

30

J.JS

rise

time)

are

featured

on

the

2225.

"Slow",

"Fast"

and "

Impulse

" all

with

"Max

.

hold"

of t

he

displayed level on

the

2226

.

Easi

ly

read "

thermometer

" display,

automatic

rese"t, and

many

other

fea-

tures

which

enable

the

operator

to

make valid and accurate

measure

-

ments

after

a

minimum

of

training

.

DC

output

of

all

functions

continu

-

ously

to

a level recorder.

FEATURES:

•

Sturdy,

compact

design

(weight

only

370

g)

•

Short-term

(one

minute)

Leq

with

up

to

50

dB

crest

fac

t

or

•

Simple

conversion

to

SEL(LAx)

•

Fulfils

IEC

651

Type

2*,

DIN

45

634

and

ANSI

S

1,4 - 197 1, Type S

2A

•

25

dB(A)

to

140

dB(A) peak

measuring

range

•

"Slow

"

and

"Fast"

time

constants

with

up

to

40

dB

crest

factor

•A-

weighted

max-hold

peak

detecto

r

(2225

only)

*

excep

t for "

Max

. hold" on

2225

19-12

1

Integrating

Sound

Level

Meter

type

2225

Integrating

Impulse

Sound

Level

Meter

type

2226

1i\

\,

•

Integ

r

ating

Sound

Level Meter

dBI" J I

I

d8(

AJ I

-~

Ill

-~

-

--

-

-::

--

-

-e ·

-=

A

....

e

·

-=

R

eNt

(B

en)

(B

•ttJ

-

-:

-

-::

--

--e

-

·-=

.2!l.

-e

·

-=

.2!l.

-O

ff

Off -

--

--}

·-

--

-

}·-

-

--

-·

-=

-

·

-=

-

--

-

m.;

-

m.;

BrUel & Kjoor

~

Type

2225

t

~

Type2226

•

A-weighted

impulse

USES:

detector

(2226

only)

•

Community

and

Industrial

•

40

dB

"thermometer

"

noise

surveys

display

with

0,5

dB

•

Determination

of

Leq

for

resolution

evaluation

of

noise

• Readable

even

in

direct

annoyance

or

hearing

loss

sunlight

risk

•

Equipped

with

robust

•

Measurements

of

non

-

B & K

Prepolarized

steady

noise

Condenser

Microphone

•

Determination

of

Sound

•

Built

in

A-weighting

Exposure

Level,

SEL(LAX)

network

•

Assessment

of

the

harmful

• Easy

one

handed

operation

effects

of

impact

noise

• DC

output

of

all

functions

(2225

only)

to

a level

recorder

•

Assessment

of

the

•

Automatic

reset

and

loudness

of

impulsive

switch

-

off

noise

(2226

only)

• "

Max.

hold"available

on •

Measurement

of

maximum

all

functions

(2226

only)

levels

(2226

only)

Introduction

Noise,

as

the

cause

of

annoyance

and

hearing

loss, is

now

a

generally

accepted

problem,

causing

many

countries

and

local

communities

to

adopt

anti

-

noise

legislation

of

var-

ious

type

and

severity

.

The

responsi-

bility

for

measuring

noise

and

en-

forcing

the

limits

often

falls

to

the

police,

health

officers,

and

other

pu-

blic

officials

who

are

not

.

them

-

selves

noise

experts

.

The

Types

2225

and

2226

have

been

de-

signed

with

these

users

particularly

in

mind

.

They

fulfil

the

need

for

a

sim

-

ply

operated,

rugged

meter

which

newcomers

to

noise

measurement

can

approach

without

apprehension

and

use

effectively

and

confidently

with

only

a

minimum

of

training

.

Nevertheless,

they

have

a

wide

range

of

facilities

hitherto

available

only

on

more

comprehensive

and

ex

-

pensive

instruments

.

The

damaging

and

annoying

ef

-

fects

of

noise

are

basically

depend

-

ent

on

3

parameters,

the

level,

the

frequency

content

and

the

duration.

The

concept

of

Leq

combines

these

parameters

into

one

unit

.

The

Types

2225

and

2226

are

not

only

normal

A-

weighted

Sound

Level

Meters

with

"Fast"

and

"

Slow"

time

constants

but

also

Leq

meters

which

integrate

automati

-

cally

for

a

period

of

1

minute.

They

differ

in

only

one

respect.

The

2225

has

a

"peak"

hold

with

30J.Lsec

rise

time

,

necessary

to

eval-

uate

the

damaging

effects

of

impul

-

sive

noise.

The

2226

has

an

inter

-

nationally

standardised

"impulse"

detector,

and

a "

Max

.

hold"

mode

on

all

functions

.

The

"thermometer"

type

display

is

by

means

of

a

row

of

41 LEOs

giving

a

40

dB

dynamic

range

with

0,5 dB

resolution

.

This

is

achieved

by

lighting

two

adjacent

diodes

to

in-

dicate

the

half

-

value

between.

Dis

-

play

brightness

is

controlled

auto

-

matically

with

respect

to

ambient

light

conditions

via a

photo-transis-

tor

and

enables

the

display

to

be

read

easily

,

even

in

direct

sunlight

.

Range

changes

automatically

bring

the

correct

values

into

view

in

the

windows

which

enumerate

the

display

scale

,

and

the

chosen

meas

-

urement

mode

is

also

displayed

in

a

2

window.

This

ensures

simple,

error-

free

read-out.

Operating

"Reset.

Batt."

displays

the

battery

condition

and

resets

the

instrument,

returning

the

display

to

the

lowest

point

on

the

scale.

Any

subsequent

measurement

starts

from

this

point,

thus

preventing

false

readings.

Measurement

re-

starts

200m

sec.

after

the

switch

is

released

so

that

local

noise

from

the

click

(which

is less

than

1

00

ms

long) does

not

interfere

with

measurement

.

Especially

important

at

low

sound

levels

and

in

the

"Peak"

mode.

In

addition,

operation

of

any

switch

initiates

the

reset

pro-

cess as

an

insurance

against

unin

-

tentional

false

readings.

The

meter

is

powered

by

3

easily

obtained

1

,5

V

alkaline

cells

(IEC

Type

LR

6)

giving

approximately

30

hours

continuous

operation

under

normal

use

.

Their

condition

is

easily

checked

on

the

display

by

operating

"Reset.

Batt

.

".

An

internal

timer

turns

the

instru-

ment

off

two

minutes

after

the

last

reset

occurs.

This

also

has

the

ad-

vantage

that

the

batteries

are

not

run

down

if

the

i

nstrument

is

accid-

entally

switched

on

while

being

transported

.

With

a level

recorder

connected

to

the

DC

output,

the

automatic

switch

-

off

is

disabled

and

on

the

2226

the

"Max

.

hold"

facility

is

overridden

so

that

sound

levels

can

be

recorded

continuously.

When

in

"60s

Leq"

mode

the

instrument

is

reset

every

60s,

the

maximum

re-

corded

value

being

the

60s

L•

eq

.

In

the

max.

hold

"Peak"

mode

the

peak

is

held

for

0,3

seconds

while

it

is recorded.

Examples

of

all possi-

ble

output

functions

are

shown

in

Fig.1.

Short-term

Leq

Measurements

Leq

is

based

on

the

equal

energy

principle

and

can be

considered

as

the

continuous

steady

noise

which

would

have

the

same

A-weighted

acoustic

energy

as

the

real

fluctuat-

ing

noise

measured

over

the

same

period

of

time.

This

calculation

is

carried

out

auto-

matically

when

measuring

in

the

"60s

Leq"

mode,

the

rising

value

of

the currently

accummulated

Leq

DDODDOOODOOOOOODDDDDDDDC

Bruel

&

Kj

oo

r

=dB (Al

--

"Siow"

--

Paper Speed 0,3

mm

/s

:=

~

70

~

60

~

50

:::=

40

1==

30

OP

01

02

100 200 Time

is)

7

8084

2

Fig.1.

The

Portable

Level

Recorder

Type

2306,

and

examples

of

recordings

made

with

2225

and

2226

in

the

various

measurement

modes

(Normalised

to

60s)

being

indicated

on

a

flashing

display

to

warn

that

the

measurement

is

still

in

prog-

ress.

On

completion

of

a

measure-

ment

the

display

stops

flashing

and

the

timer

allows

a

one-minute

read-

out

period

before

turning

the

instru-

ment

off

unless

a

reset

occurs

dur-

ing

this

time

.

Operating

any

switch

causes

a

reset.

The

important

advantage

of

dis-

playing

the

normalised

Leq

is

that

SEL(LAx )

can

be

obtained

easily

as

soon

as

the

event

is

over,

simply

by

adding

10

log

10

60,

(approx

.

18

dB)

to

the

reading

. SEL

(Sound

Expo-

sure

Level) is

the

sound

level

which

,

if

maintained

constant

for

a

period

of

1

second,

would

contain

the

same

A-weighted

energy

as

the

actual

event.

This

is a

useful

par

-

ameter

for

comparing

single

events

of

different

levels

and

duration,

or

in

building

up

a

long

term

Leq

from

a

knowledge

of

individual

events

and

their

frequency

of

occurrence.

Calibration

is

easily

carried

out

us-

ing

Sound

Level

Calibrator

Type

4230,

which

fits

directly

over

the

microphone

producing

93,8

dB

(±

0,25

dB).

A

windscreen

is

supplied

and

s

hould

always

be

used

when

mak-

mg

outdoor

measurements.

Description

A

composite

block

diagram

is

re-

pro

duced

in

Fig.2. A Prepolarized

Co

ndenser

Microphone

is

fitted,

which,

combined

with

the

small

size

of

the

meter

case,

gives

the

overall

frequency

and

directional

chm

acteristics

shown

in

Figs. 3

and

4 . The

attenuator,

which

splits

the

dy

na

mic

range

into

four

overlapping

40

dB

measuring

ranges,

is

fol-

low

ed

by

a

permanently

connected

A-w e

ighting

network.

The

weighted

signal is

fed

to

a

logarithmic

recti-

fier

which

performs

a

full

-

wave

rec-

tific

il

tion

and

outputs

the

result

in

logar

ithmic

form.

The

detector,

which

performs

true

RMS

detection,

has

the

two

standar-

dized

time

constants

"Fast"

and

"

Slow

".

In

addition

Type

2225

has

a "Pe

ak"

hold

with

30

JJ.S

rise

time

,

and

the

Type

2226

an

"Impulse"

dete

ctor

to

IEC

and

DIN

specifica-

Overload

Detector

~

(2226 Display

only)

Microphone •

p-

A·

Peak

(2225)

or

Pream-

...

Attenuator

~

Weighting

~

Log.

~

Impulse (2226)

~

DC

plifier

Rectifier Detector

Amplifier

Network and Integrator

Jt

t

D~

-=--

DC

Reset Function

-Timer

f-4-

and

.......

-

""'[_____

Converter Control Selector

Output

780791

Fig

.

2.

Composite

Block

Diagram

of

Types

2225

and

2226

dB

6

4

2

0

-2

-4

-6

10

dB

8

6

4

2

0

-2

-4

-6

-8

~

' '

./

100 Frequency (Hz)

.............

:""'.....

--

("'

I

l

20 100

l I

~

IEC

651

Type 2

1--

-

""""

---

v

ll

0° incidence

....

~

r-

1-o...

......

...

1k

.,..-

......

~

......

v

I-'

1-"'

......

~

.............

.........

...........

1k

?...

'-

10k 20k

790096

/ 1

AN~I

s\,4-

~97~-

Type S2A

--=

£

,

Random incidence

"-

\'

I

10k 20k

Frequency (Hz) 7

900

95

Fig.3.

Free-Field

frequency

response

of

the

complete

instrument

to

sine

waves

with

0°

inci-

dence

(upper)

and

random

incidence

frequency

response

(lower)

Fig

.

4.

Directional

Characteristics

of

the

complete

instrumen

t

tions.

For

calculating

a

short-term

average

sound

level

in

the

"60s

Leq"

mode,

the

detector

output

is

squared

and

integrated

,

the

process

being

controlled

by

the

timer

.

Crest

factor

capability

of

the

detector

is

high,

up

to

50dB

. (See Speci

fica-

tions).

3

The

DC

amplifier

drives

the

dis-

play

and

the

DC

output,

which

is

in-

tended

for

use

with

level

recorders,

providing

a

DC

voltage

proportional

to

the

dB

value

of

the

measured

sig-

nal

with

the

same

dynamic

range

as

the

instrument.

2226

only

An

overload

detector

monitors

both

the

input

to

the

attenuator

and

the

output

from

the

A-weighting

ne-

twork,

and

the

display

flashes

at

full

scale

if

an

overload

is

detected.

In

addition,

on

this

instrument,

the

maximum

sound

pressure

level is

held

on

the

display

until

reset,

con-

tinous

operation

of

the

display

be-

ing

obtained

when

the

"DC

Output"

plug

is

inserted,

or

when

the

"DC

Output"

push-button

supplied

is de-

pressed.

Specifications

2225

and

2226

Measuring

Range:

25

dB(A)

to

140

dB(A) peak in 4

ranges

20-

60dB(A)

50-

90dB(A)

80

- 1

20

dB(A)

100-

140dB(A)

Frequency

Response:

See

curves

Figs.3 and 4

Frequency

Weighting

:

A-weighting

Detector:

Characteristics

:

RMS

and

Peak

(2225)

or

Impulse

(2226)

in accordance

with

IEC

651

* Type 2,

DIN

45634

and

ANSI S.1 .

4-1971

Type

S2A

Dynamic

Range:

60

dB(A)

(40

dB(A) on scale +

20

over)

Limited

by

measuring

range

Crest

Factor:

20

dB at

upper

limit

of

measuring

range,

rising

linearly

with

decreasing

signal

le-

vel

to

a

maximum

of

40

dB

for

Sound

Le-

vel

and

50

dB

for

leq

Time

Constants:

"Slow"

and

"Fast"

to

IEC

651

2225

only:

"Peak

hold"

better

than

±0,

1 dB/ s

with

30

IJS

rise

time

2226

only:

"Impulse

"

to

DIN,

IEC

"Max.

hold"

on "Fast

",

"

Slow",

and

"Im-

pulse"

better

than

±0

,1 dB/ s

Display:

"Thermometer"

type

display

with

41

LEOs

giving

a

40

dB range

with

0,5

dB

display

resolution.

Overrange

and

under-

range

warning

Linearity:

Better

than±

0,25dB

•

except

for

"Max

.

hold

"

on

2225

Read

out

interval:

Read-out updated

1000

times

per sec-

ond

Brightness:

Automatically

controlled

with

respect

to

external

light

level.

Visible

even

in

direct

sunlight

DC

Output:

Output

impedance

: 10 kO,

short

circuit

proof

Nominal

output

voltage:

50

mV

/dB

Offset

:

bottom

of scale = 0 V

Reset

Function:

Operation

of

"Reset

(Batt.)"

or

any

func-

tion

resets all

time

constants

and

re-

starts

measurement

200

msecs

after

re-

lease

Automatic

Switch-off:

Instrument

turns

off

automatically

2

min-

utes

after

the

last

switch

is operated, ex-

cept

when

the

"DC

output"

plug is

being

used.

Microphone:

Type:

1/

2-inch

B & K Prepolarized Con-

denser

Microphone

Type

4175

Sensitivity:

50

mV

/

Pa

Capacitance:

12 pF

Calibration:

Screwdriver

operated

potentiometer

ad-

justment

using

Sound

Level

Calibrator

Type

4230

Reference

Conditions

for

Calibration

Valid-

ity:

Type

of

Sound

Field:

Free

Reference

Incidence

direction:

Per-

pendicular

to

microphone

diaphragm

Reference

SPL:

94

dB (re

20

11Pa)

Reference

Frequency:

1 kHz

Reference

Temperature:

20°C

Reference

Measuring

Range:

80

-

120dB(A)

Effect

of

Magnetic

Field:

(at

50

Hz,

80

Ai m

(1

0rsted))

<

20

dB(A)

Effect

of

Humidity:

(at

40°C

(1

04°F),

1000Hz)

<

0,5

dB

change

in

sensitivity

in

the

range

of

relative

humidities

from

65%

to

90%

Effect

of

Temparature:

(at

1000Hz)

Temperature

range

-1

0

to

±

50°C

(re

20°C)

Temperature

coefficient

of

·

microphone-

/

preamplifier

-0,025

d8

/°C

Temperature

coefficient

of

complete

in-

strument

-0,025

(±

0,016)

d8

/

°C

Warm-up

time:

< 1 s

Batteries:

Type:

Three

1,5 V

Alkaline

cells IEC type LR 6

(B

& K

order

No. QB

001

3)

Life:

Approx

.

30

hours

continuous

normal

use

Approx

. 10

hours

in

maximum

sunlight

Overall

Dimensions:

201

X

72

X

22

mm

(7

,9 X

2,8

X 0,9 in)

Weight:

370

g

(0

,81b)

with

batteries

Accessories

included:

1

half-inch

Prepolarized

Condenser

Mic

-

rophone

Type

4175

1

Leather

carrying

case

KE

0177

1 2,5

mm

mini

-

jack

plug

JP

0213

1

Windscreen

UA

0459

3

cells

QB

0013

Accessories

Available:

Sound

Level

Calibrator

Type

4230

Level

recorder

cable

AO

0173

3 m

microphone

extension

cable

AO

0185

with

threaded

attachment

(UNC

1/

4"

x

20)

for

direct

connection

to

tripod

10m

cable as above

AO

0186

DUST CAP:

WINDSCREEN:

MICROPHONE:

2.

CONTROLS

Dustcap

S•:::~~~,::~~:~

•

lntegr•ting

Sound

level

Meter

dBI

A)

I

-~

-Windscreen

---

Function Selector

Display Scale

-

...

·-=

ReMt

IB•~l

!?!!..

Off

Reset and

Battery Check

--On-Off

~

DCOutput

·-=

}·B•n•rv

----

Battery Condition

indicator scale

g.;

Briiel

8c

Kja&r

• Type

2225

790002

Fig.2.1.

Front

view

of

the

Type

2225

To

protect

the

Microphone

from

dust

and

dirt.

Except

when

calibrating

the

instrument,

either

the

dustcap

or

windscreen

should

always

be

in

place.

Reduces

wind

noise

and

protects

the

Microphone

from

dust,

dirt

and

light

precipitation.

Remove

the

dustcap

before

fitting

the

windscreen

as

it

may

be

lost

inside.

8 & K

half

inch

Prepolarised

Condenser

Microphone

Type

4175.

Al-

though

the

Microphone

cartridge

can be

unscrewed

from

the

adaptor

this

is

not

recommended.

The

black

protection

grid

at

the

top

of

the

microphone

is

not

removable.

Special care

should

therefore

be taken

to

make

sure

that

foreign

matter

does

not

fall

through

the

grid.

5

MICROPHONE ADAPTOR:

The

adaptor

connects

the

microphone

to

the

Sound

Level

Meter

via a

standard

5-pin

DIN

plug.

Note:

Operating

any

of

the

following

four

switches;

ON-OFF, RESET (BATT.), FUNCTION

SELECTOR,

or

RANGE SELECTOR,

causes

the

instrument

and

the

timer

which

controls

L

eq

measurement

and

the

automatic

"switch-off''

facility

to

be reset.

ON-OFF:

RESET (BATT.):

FUNCTION SELECTOR:

RANGE SELECTOR:

DISPLAY:

SENSITIVITY

ADJUSTMENT:

6

Push-button

for

switching

the

instrument

on

and

off.

The

display

should

operate

immediately

when

switched

on.

The

instrument

switches

off

automatically

two

minutes

after

last reset.

This

feature

is

overridden

when

the

DC

OUTPUT

plug

is

inserted.

Push-button

switch

which,

when

pressed,

displays

the

battery

condi-

tion

on

the

scale.

If

the

level is

below

the

BATTERY

region

of

the

scale,

the

batteries

must

be replaced. See

Section

3.2.

This

switch

also resets

the

meter,

i.e.

it

starts

a

new

measurement

in

60s

Leq

mode,

resets

the

peak

hold

and

RMS

detectors

and resets

the

auto-

matic

"switch

-off"

time.

Four

position

slider

-

switch

as

follows:

"Fast"

provides

the

standardised

"Fast"

detector

response

for

measur-

ing steady

sound

levels.

"Slow"

provides a

"Slow"

detector

response

for

use

when

the

sound

level

fluctuates

too

rapidly

in

the

"Fast"

mode

for

accurate

reading.

"60s

Leq"

Integration

of

the

sound

level

takes

place

for

a

fixed

period

of

one

minute

during

which

the

flashing

display

indicates

the

current

accummulated

dose.

When

measurement

is

completed,

the

display

stops

flashing

and

the

60s

L

eq

is

indicated

for

a

read-out

period

of

one

minute.

The

instrument

is

then

automatically

switched

off

if

none

of

the

instrument's

switches

are

operated

during

this

period

.

"Peak"

(2225

only)

holds

the

maximum

peak

value

until

the

meter

is

reset. Rise

time

is

30J.LS.

"Impulse"

(2226

only)

Provides

the

"Impulse"

detector

response

for

the

evaluation

of

the

subjective

response

of

impulsive

sounds

.

Note:

If

an overload is

detected

in

any

mode,

the

display

of

the

2226

flashes

at

full

scale

deflection.

A

four

position

slider-switch

for

selection

of

four

overlapping

measur-

ing ranges.

Windows

at

10 dB

intervals

alongside

the

display

serve

to

enumerate

the

scale

automatically.

40

dB

"Thermometer"

type

display

with

41 LEOs

giving

a

read-out

res-

olution

to

0,

5 dB

(two

adjacent

LEOs on).

The

display

brightness

is

con-

trolled

by a

photo-transistor,

and

is readable even

in

direct

sunlight.

Uppermost

or

lowermost

LEDs

indicate

out-of-range.

Removing

a

small

plastic

plug

gives

screwdriver

access

to

the

poten

-

tiometer

.

The

gain

may

be

adjusted

(over a 10 dB range)

to

allow

for

small

variations

in

microphone

or

meter

sensitivity.

Fig.2.2.

Right-hand

side

view

of

the

Type

2225

or

2226

showing

DC OUTPUT

socket

DC OUTPUT:

Socket

providing

a

DC

voltage

proportional

to

measured

level

(50

mV

/dB).

Output

impedance

10

kO.

Accepts

2,5

mm

mini

-

jack

plug

(B

& K No.

JP

021

3).

When

in

use

the

automatic

switch-off

is

dis-

abled,

and

in

addition,

in

the

case

of

the

2226,

"Max.

hold"

is

overrid-

den

and

normal

continuous

operation

of

the

instrument's

display

is ob-

tained

. Levels can be

continuously

fed

to

a

recorder

in

"Fast",

"Slow"

and

"Impulse"

(2226

only). In

"60s

Le

q"

the

accummulated

dose

is

output

until

the

60s

Leq is

reached

after

one

minute

and

then

the

measurement

is

restarted

. In

"Peak"

(2225

only),

the

maximum

peak

detector

is reset

automatically

whenever

a

higher

peak

occurs

.

The

peak

value

is held

for

a period

of

0,3

s,

after

which

the

detector

is

reset,

unless

a

higher

peak

value

occurs

during

that

time,

causing

an

immediate

reset. The stored peak

value

is

output

continuously.

With

the

2226

only,

overload is

indicated

by a

high

DC

output.

TRIPOD

MOUNTING

BUSH: Located

near

the

bottom

of

the

rear

of

the

instrument

case.

The

thread

is UNC 1I

4"

x

20,

the

standard

tripod

mounting

thread.

7

3.

OPERATION

3.1.

INTRODUCTION

This

Instruction

Manual

describes

the

specific

procedures

necessary

to

use

the

Integrat-

ing

Sound

Level

Meter

Type

2225

and

Integrating

Impulse

Sound

Level

Meter

Type

2226

correctly.

However,

many

other

more

general

aspects

of

sound

measurement

must

be

considered in

order

to

be

sure

of

obtaining

accurate,

reproducible

measure-

ments.

Many

of

these

are

discussed

in

the

accompanying

booklet

"Measuring

Sound"

which

should

be read in

conjunction

with

this

Instruction

Manual.

In

addition,

for

many

purposes

measurements

may

have

to

be

made

in

a

way

and

with

equipment

which

are closely

specified

by

National

or

International

standards,

e.g.

air-

craft

noise

or

industrial

hearing

damage

risk

measurements.

Failure

to

comply

with

these

standards

may

result

in

invalid

data.

It is

therefore

recommended

that

reference

be

made

to

the

standards

applicable

to

the

particular

measurement

situation.

3.1.1.

General Considerations

1.

Store

the

instrument

in a

dry

warm

place.

2.

Remove

batteries

if

stored

for

a

long

time.

3.

Connect

microphones

or

adaptors

with

power

off.

4.

Use

light

finger

torque

only

when

fitting

the

microphone

to

the

adaptor.

5.

Keep

dust

and

foreign

objects

away

from

the

microphone

diaphragm.

3.2.

BATTERY

INSTALLATION

8

The

Types

2225

and

2226

are

powered

by

three

1,5

V

alkaline

cells,

IEC Type

LR6

(B & K QB

0013).

These are

inserted

into

the

rear

of

the

instrument

as

shown

in

Fig.3

.1

after

making

sure

the

instrument

is

"Off"

and

sliding

off

the

battery

compartment

cover.

Bruel

&

Kjaer

~

Type

2225

Fig. 3. 1.

Battery

replacement

The

polarities

should

be as indicated

on

the

case.

New

cells

will

provide

about

30

hours

continuous

operation

in

normal

conditions,

or

10

hours

in

direct

sunlight.

Batteries

should

be replaced

whenever

the

battery

condition

indication,

obtained

by

pressing

RESET

(BATI.),

falls

below

the

region indicated on

the

display.

It

is

recommended

that

only

alkaline

batteries,

such

as

those

supplied

with

the

instru-

ment,

are used.

3.3.

MOUNTING

THE

MICROPHONE

The

microphone

is

screwed

directly

onto

the

adaptor,

using

light

finger

torque.

The

as-

sembly

may

then

be

plugged

directly

into

the

sound

level

meter

via

its

5

DIN

plug

(see Fig.

3.2)

or

connected

via a

3m

or

10m

extension

lead

available

under

order

num-

bers

AO

0185

and

AO

0186

respectively. The

microphone

end

of

the

extension

lead

has a

threaded

attachment

to

enable

it

to be

connected

directly

to

a

standard

tripod

screw.

This

arrangement

allows

the

operator

to

be close

to

the

sound

level

meter

for

reading

purposes,

while

at

the

same

time

enabling

him

to

be

well

away

from

the

micro-

phone,

and

therefore

not

influence

the

sound field.

----::-

::

---

-

~

Fig. 3. 2.

Microphone,

adaptor

and

connection

to

the

sound

level

meter

3.4.

CALIBRATION

The

Sound

Level

Calibrator

Type

4230

is

recommended

for

acoustical

calibration

of

the

whole

instrument,

including

microphone.

The

4230

is

basically

a

miniature

loudspeaker

with

a

stabilised

output

of

94

(±

0,25)

dB (re.

20

x

10-

6 Pa.)

at

1 kHz. The

calibration

procedure

is as

follows:

1.

Mount

the

microphone,

switch

power

on and press RESET.

BATI.

to

check

the

bat-

teries

of

the

Sound

Level

Meter.

The

instrument

will

switch

off

automatically

two

minutes

after

a Reset

occurs.

2. Fit

the

Sound

Level

Calibrator

with

the

half-inch

adaptor.

(B

& K

part

No. DB

0311)

3. Remove

the

dust

cap

or

windshield

from

the

microphone

and

fit

the

calibrator

over

the

microphone

so

that

it

seals properly. See

Fig.3.3.

4.

Set

the

RANGE SELECTOR

to

the

"80

to

1

20

dB(A)"

range

and

FUNCTION SELEC-

TOR

to

"Fast"

detector

setting.

5. Remove

the

small,

push-fit,

plastic plug on

the

top

front

of

the

instrument

to

gain

ac-

cess

to

the

sensitivity

adjustment

potentiometer.

9

Fig.

3. 3. Calibrating

the

instrument

6.

Switch

the

Calibrator

on

and

adjust

the

potentiometer

with

a

small

screwdriver

as

in

Fig.3.3

so

that

the

LED

at

the

93

dB

position

just

extinguishes

but

the

94

dB LED is

lit

when

"moving

up"

the

scale,

i.e

.

turning

the

sensitivity

potentiometer

screw

clockwise

.

This

gives a

calibration

of

93,8

dB

to

correspond

with

the

half-inch

free-

field

microphone

sensitivity,

with

an

accuracy

of

±0,

1 dB:

This

process is made easier

with

the

Type

2226

if

the

DC

Output

plug

is

inserted

to

override

the

"Max.

hold"

facility.

This

gives

a

display

which

is

continuously

adjus

-

table

both up and

down

instead

of

held

at

the

max

i

mum

value

by

the

"Max.

hold"

circuit,

requiring

continual

resetting

.

7.

Remove

the

Calibrator

gently.

It

will

turn

off

automatically

.

8. Replace

the

dustcap

or

windscreen.

The

Sound

Level

Meter

is

now

calibrated

and

ready

for

use.

3.5.

SOUND

LEVEL

MEASUREMENTS

3.

5.1.

General

10

The

accompanying

booklet

"Measuring

Sound"

should

be read

before

proceeding

with

measurements.

Always

use a

Windscreen

outdoors

or

in

dusty

environments

and

ensure

that

the

measuring

position

is

suitable

and

that

the

background

noise

level is

low

enough

to

make

valid

readings.

In

order

to

minimise

the

effect

of

reflections,

the

obser-

ver

should

hold

the

instrument

at

arms

length

or

mount

the

microphone

remotely

on

a

tripod

using

a

connection

cable.

3.5.2.

Procedure

for

Sound

Level

Measurements

1.

Calibrate

the

meter

and

check

the

batteries.

See

Section

3.4.

2.

Set

the

FUNCTION SELECTOR

switch

as

follows:

"Fast"

"Slow"

"60S

L

eq"

"Peak"

"Impulse"

for

normal

sound

level

measurements.

if

the

display

fluctuations

in

the

"Fast"

position

are

too

large

or

too

fast

for

accurate

readings.

If

a

longer

averaging

time

is

required

to

obtain

meaningful

short

term

measurements

of

fluctuat-

ing

or

cyclical

noise,

or

when

an

Leq,

noise

dose,

or

SEL(LAx)

is

required

directly.

For

example,

for

the

evaluation

of

noise

annoyance

(Leq

),

the

as-

sessment

of

hearing

damage

risk

(noise

dose),

or

comparison

of

the

annoyance

of

similar

events

(SEL(L AX)).

(2225

only)

to

hold

the

maximum

peak

value

of

the

signal.

(2226

only)to

obtain

the

subjective

level

of

impul-

sive

sounds.

Note:

The

normal

mode

of

operation

of

the

Type

2226

is

"Max.

hold".

Continuous

display

of

fluctuating

Sound

Pressure Levels can be

obtained

simply

by

inserting

the

"DC

Output"

plug.

3.

Set

the

RANGE SELECTOR

switch

so

that

the

level

indicated

is

in

a

convenient

posi-

tion

on

the

display

which

does

not

exceed

full

scale

or

cause

overload.

4. It

may

sometimes

be

necessary

to

make

measurements

in

the

presence

of

back-

ground

noise,

which

will

contribute

to

the

measured

level

and

for

which

a

correction

~

Cl

6

c

~

\

-ro

s 5

E

_g

14

.0

~

3

<1>

.0

B

co

"0

2

0

<1>

.0

E

::J

z

~

\

~

\

'\

I"

"

""-

.........

.......

...........

r--..

1-o....

.........

~

r--

-

0 0 2 3 4 5 6 7 8 9 10 dB

Difference between total reading and background reading

171139

Fig. 3.4.

Correction

curve

for

the

influence

of

background

noise

11

must

be

made.

Readings

should

be

made

for

the

source

operating

in

the

presence

of

background

noise,

and

for

the

background

noise

alone.

A

correction

can

then

be

made

according

to

the

curve

of

Fig.

3.

4.

The

difference

between

the

two

values

is

found,

and

the

correction

curve

is

entered

on

the

horizontal

axis

at

this

value.

The

corresponding

correction

value

obtained

from

the

vertical

axis

is

then

subtracted

from

the

higher

of

the

two

measured

values.

5.

To

make

a

new

measurement

in

"60s

L

eq,

"Peak"

(2225

only)

or

"Max

.

hold"

(2226

only)

mode,

press RESET (BATT.)

3.5.3.

Noise

Dose

Measurements

What

the

instrument

measures

in

the

"60s

L

eq"

mode

is a

noise

dose

referred

to

min-

ute

.

If

this

L

eq

is

referred

to a

time

duration

of

8

hours

by

subtracting

approx.

26,8

dB

(10 log

10

(8

x

60))

it

can be

expressed

as a

percentage

of

the

allowable

dose

for

that

pe-

riod.

A

nomogram

for

estimating

the

percentage

of

allowable

noise

dose

for

an

8

hour

working

day

from

the

meter

reading

is

reproduced

in

Fig.3.5.

This

applies

to

ISO

only.

Allowed 8 hours

Leq-value

80

dB

85

/

90

/

Noise dose in %

of

max. allowable dose

/

800

/

400 /

/

200

/

100%

0

60s

Leq

-value dB

/

/ /

/

/115

110

105

100

95

90

SEL Value

125

780873

Fig

.

3.

5.

Nomogram

for

estimating

daily

noise

dose

or

SEL(L

Ax)

from

meter

reading

3.5.4.

SEL(lAx)

Measurements

12

SEL is

the

Sound

Exposure Level

and

is

basically

an

Leq

normalised

to

a

duration

of

1

second.

It

is used

primarily

to

rate

individual

noise

events,

either

to

compare

them

with

regard

to

annoyance,

or

to

evaluate

an

overall

noise

climate

by

combining

a

number

of

individual

events

whose

level

and

frequency

of

occurrence

are

known.

The

procedure

is

exactly

as

in

3.

5.2,

for

"60s

Leq"

measurement,

except

that

the

reading

may

be

taken

as

soon

as

the

event

is over,

without

waiting

for

the

full

minute

measuring

period

to

elapse.

To

this

measured

value

just

add

approx.

18

dB

(10 log

10

60)

to

convert

to

SEL

(LAx).

4.

USE

WITH

OTHER

INSTRUMENTS

4.1.

DC

LEVEL

RECORDING

The

Portable Level Recorder Type

2306

is

well

suited

for

use

with

the

Types

2225

and

2226,

being

operated

from

internal

batteries.

It is

connected

directly

to

the

"DC

OUT-

PUT"

of

the

meter

via a cable

(B

& K

order

Number

AO

0173)

with

a

standard

BNC

plug

at

the

recorder

and a

standard

2,5

mm

mini

jackplug

at

the

meter.

When

this

is

inserted

it

overrides

the

automatic

"switch-off"

feature

and

the

"Max.

hold"

mode

of

the

2226

al-

lowing

the

meter

to

run

continuously

in all modes

of

operation.

In

"60s

Leq"

the

accu-

mulated

value

is

continously

recorded,

the

final

value

being

the

Leq

for

one

minute,

and

the

meter

is reset

to

start

a

further

"60s

Leq"

measurement.

In

"Peak"

(2225

Only),

the

maximum

peak is held

for

0,3

s

and

then

reset,

unless

a

higher

peak

occurs

during

that

time,

causing

an

immediate

reset.

The

procedure

is as

follows:

1.

Calibrate

the

meter

(including

checking

the

batteries) as

in

Section

3.4.

2.

Ensure

that

the

POLARITY REVERSER

of

the

2306

is

in

the

+

position

and

that

no

leads are

connected

to

SIGNAL

INPUT.

3.

Set

RECORDING

MODE

slider-switch

on

the

2306

to

"DC

Lin"

and

select

the

re-

quired

writing

and paper speed. A

250

mm/s

writing

speed is

recommended

as

this

is

fast

enough

to

faithfully

reproduce

the

levels

even

in

the

"peak"

mode

of

the

2225.

4.

Using

DC

LIN POSITION

adjust

the

pen position

to

lie

exactly

on

the

lower

line

of

the

paper. See Fig.4.1 .

Fig. 4.

1.

Calibrating

the

Type

2306

using

the

Type

4230

calibrator

5.

Connect

the

DC OUTPUT

of

the

Type

2225

or

2226

to

the

SIGNAL

INPUT

of

the

2306

using

cable

AO

0173.

6. Place

the

Sound

Level

Calibrator

Type

4230

over

the

microphone,

switch

on

both

calibrator

and

sound

level

meter

and

set

FUNCTION SELECTOR

to

"Fast".

13

14

7.

Slide

the

RANGE SELECTOR

of

the

meter

to

give

the

50

to

90

dB(A)

range.

8.

Adjust

the

SENSITIVITY

potentiometer

on

the

2306

so

that

the

pen

lies

exactly

on

the

third

line

from

the

top

of

the

recording

paper.

This

position

should

be

noted

as

the

94

dB

calibration

level. See Fig

.4.

1.

The

meter

will

indicate

full

scale

deflection

(

90

dB(A)),

but

the

DC

output

will

be

unaffected

i.e.

it

will

give

an

output

correspond-

ing

to

94

dB as

the

instrument

has

20

dB

extra

range

over

that

displayed.

9.

Select

suitable

measuring

range

on

the

RANGE SELECTOR

and

set

FUNCTION SE-

LECTOR as

required.

Remember

to

note

the

range

used

on

the

Level

Recorder

paper.

For

any

range

chosen

the

bottom

line

on

the

paper

corresponds

to

the

lowest

value

on

the

instrument

display

scale,

when

the

above

procedure

is

followed.

The

Level

Recorder is

now

calibrated

and

ready

for

use.

Alternative

Calibration

Method

The

following

procedure

can be

carried

out

without

using

a

calibrator,

but

therefore

as-

sumes

that

the

Sound

Level

Meter

is

itself

correctly

calibrated.

1.

Carry

out

steps 2

to

5 as above

2.

Slide

the

RANGE SELECTOR

of

the

meter

to

give

the

range

50

to

90

dB(A)

and

se-

lect

60s

Leq

on

the

FUNCTION SELECTOR.

3.

Obtain

a steady reading

in

the

upper

region

of

the

display,

by

clapping

the

hands

for

example

.

As

an example, suppose a

reading

of

84

dB(A) is

obtained

.

4.

Adjust

the

pen

position

using

the

SENSITIVITY

potentiometer

of

the

2306

so

that

it

indicates

the

displayed

value

on

the

paper.

(See

Fig.4.2)

The

top

of

the

meter

dis-

play

should

correspond

to

the

2nd

thick

line

from

the

top

of

the

recording

paper

and

the

bottom

of

the

display

correspond

to

the

bottom

line

on

the

paper

.

5.

Select

suitable

measuring

range

on

the

RANGE SELECTOR

and

set FUNCTION SE-

LECTOR as

required.

Remember

to

note

the

range

used on

the

Level

Recording

Paper. For

any

range

chosen,

the

bottom

line

of

the

paper

corresponds

to

the

lowest

value

on

the

instrument

display

scale,

when

the

above

procedure

is

followed.

ODDOOODODODOODODDOOOOODC

1

OO

Br

ii

el &

Kj

oo

r

Meter

Display

90

-

r---

Ref.

so

::::r=

ltem 4

70

60

Scale

Bottom 50

QP

0102 7

80898

/ 1

Fig. 4.2.

Calibrating

the Type

2306

using

Alternative

method

Typical

examples

of

recordings

made

w i

th

various

meter

functions

are

shown

in

Fig.4

.3.

BRUEL & KJAER 2225 User manual

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