Brüel & kjær 2218 User manual

Instruction

Manual

Precision Integrating Sound Level

Meter

Type

2218

• •

8riWtlli~

..

T.,..2211

033-0292

A precision sound level meter

with

analog

readout and an

Leq

meter

with

digital read-

out combined in one compact battery-oper-

ated unit. It measures

Leq

to

ISO

R

1996,

R

1999

and

DIN

45

641 , and

SEL.

It com-

plies

with

IEC

651.

Type 1 (Impulse), and

ANSI

S1.4-1971,

Type 1. The

RMS

detec-

tor has the standardized Impulse, Fast and

Slow time constants and a

Peak

facility

with

50ps

rise time. Max. Hold is available

on all time constants. The full measuring

range of

25

to

145

dB

is covered in three

overlapping

80

dB

ranges.

"A"

or Lin.

(20Hz

to

'20kHz) frequency weighting.

AC

and

DC

outputs for connection of recorders.

Leq

or

SEL

is displayed on a 3 1

/2-digit

dig-

ital display. Alternatively, elapsed time and

preset time can

be

displayed. Maximum

measurement time is 27,7 hours. Measure-

ment time can be preset. Sockets for exter-

nal filters such

as

Type

1613

or

1616

al-

low

for measurement

of

Leq

in octave or

1/3

octave bands and noise analysis, both

A-weighted and linear.

+ Briiel &Kjaer

PRECISION

INTEGRATING

SOUND

LEVEL

METER

TYPE

2218

Applicable

to

instruments

from

serial

No.

926

961

Revision

March

1

981

CONTENTS

1.

INTRODUCTION

AND

SPECIFICATIONS

(PRODUCT

DATA)

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

1

2.

CONTROLS

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

......

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

..

........ 9

3.

OPERATION

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

14

3.1.

INTRODUCTION ..................................................................................

..

14

3.2.

POWERING

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

14

Battery

Operation

.................................................................................... 14

Recharging

of

NiCd-cells and Line Operation ...

.....

...

..

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

.

..

15

Battery Check ......................................................................................... 16

Battery Check

of

Keep-alive

Battery

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

..

........ 16

3.3.

MOUNTING THE MICROPHONE

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

16

3.4.

CALIBRATION .

.......

.

......

.

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

..

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

..

.......

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

.

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

17

General

.....

...

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

..

...........

.

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

.

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

17

Acoustical

Calibration ........................................................................

..

.... 17

Calibration using

the

Internal

Reference Voltage ......................................... 19

3.5.

SOUND LEVEL MEASUREMENTS

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

20

General

.......

..

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

20

Procedure

for

Sound

Level

Measurements

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

21

3.6.

Leq

-MEASUREMENTS ....

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

21

General

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

..

........

.

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

......

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

21

Presetting

Measurement

time

...

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

22

Procedure

for

Leq

-measurements

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

....

.........

23

Procedure

for

SEL

measurements

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

..

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

23

Noise Dose

Measurements

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

24

3.7

. CALIBRATION

FOR

VIBRATION MEASUREMENTS

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

25

General ....

..

..........

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

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

....

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

.

...........

25

Calibration ...

..........

.........

......

....

..

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

..

.......

...

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

..

.........

....

25

3.8.

VIBRATION MEASUREMENTS

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

26

General

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

...

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

...

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

.......

..

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

26

Procedure

for

Vibration

Measurements

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

26

Calculation

of

Vibration

Amplitude

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

26

4.

USE

WITH

OTHER

INSTRUMENTS

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

29

4.1.

GENERAL

.........

.......

..

....

..

.

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

29

4.2. LEVEL RECORDING

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

29

AC Recording ..........................................................................................

29

DC

Recording ..........................................................................................

30

5.

MISCELLANEOUS

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

..

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

..

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

..

.........

32

5.1.

INPUT STAGE CONNECTIONS

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

.

......

..

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

32

FEATURES:

•

Direct

indication

of

Leq

to

ISO R

1996,

R

1999,

DIN

45

641

and

of

SEL

• L8q

updated

once

every

second

•

Display

of

elapsed

time

•

Preselection

of

measuring

period

•

Analog

read-out

of

SPL

on

linear

50

dB

meter

scale

• Fast,

Slow

and

Impulse

time

constants

to

IEC

651

Type 1 (Imp.)

and

Peak

(<50

fJ.S

rise

time)

•

Max.

Hold on all

time

constants

•

True

RMS

detector

•

80

dB

dynamic

range

and

high

crest

factor

capability

•

Built-in

"A"

and

"Lin"

(20Hz

to

20kHz)

frequency

weighting

•

One

compact,

battery

operated

and

portable

unit

•

AC

and

DC

outputs

•

Provision

for

connection

of

system-matching

filter

sets

•

Delivered

with

individually

calibrated

1

/2"

condenser

microphone

•

Built-in

long-life

battery

protects

memory

content

•

Wide

selection

of

accessories

•

Performs

as

vibration

meter

or

analyzer

when

combined

with

appropriate

accessories

035

-81

The

221e

is

both ari analog sound le-

vel meter

with

a

wide

dynamic range

and

an

~

Sound Level Me-

ter.

or

Leq

Meter

with

digital

read-

out.

It

is

used

to

obtain

all

conven-

tional

sound

level

meter values, plus

a single number description

of

traffic

noise, community noise, industrial

noise (ISO noise

dose),

as well as

noise emission

of

cyclical

machines.

It can in addition compute

the

SEL

value for characterising single

events. The

2.,21

8 is also

of

great

benefit on

the

type

of

fluctuating sig

..

nal

where

the

di;J{A)

"Slow"

reading

is

not

stable.

..

Both

the

integrated

sound level

a'nd

the elapsed

time

over

which

the integration takes

place can be displayed. The integra-

tion time may be preselected. The

2218

also functions as an impulse

precision sound level meter

with

a

peak facility

(<

50

ps

rise time), and

the

"Max

.·

Hold"

mode

is

selectable

on all time co

Y,

stants. Optional fre-

quency analysts and tape recording

capabilities.

USES:

•

Determination

of

Leq

for

assessment

of

risk

of

hearing

loss

or

noise

annoyance

•

Measurement

of

cyclical

machine

noise

• S

hart

duration

noise

dose

measurements

•

Investigation

of

noise

dose

distribution

versus

locality

and

time

•

Noise

and

vibration

measurements

and

analyses

•

Max.

level

measurements

of

e.g.

aircraft

flyovers,

vehicle

drive-bys

type

2218

Precision

Integrating

Sound

Level

Meter

-

• •

-·-

+

T,..u••

t·

___

,__

Problems

caused

by

noise

are

be-

coming

more

severe

in

our

modern

industrialized

society

because

of

in-

creasing

noise

levels.

Noise

can

cause

loss

of

hearing,

or

it

can

an-

noy

us

and

disturb

our

various

activ-

ities.

In

both

cases,

its

harmful

or

annoying

effect

is

basically

a

ques-

tion

of

its

level,

duration

and

fre-

quency

content.

These

three

factors

are

combined

in

the

concept

of

Equivalent

Continuous

Sound

Level,

Leq

.

The

221

8 is

an

Leq

meter

with

digital

read-out

and

a prec1s1on

sound

level

meter

with

analog

read-

out

combined

in

one

compact,

bat-

tery

operated

and

portable

unit

fea-

turing

a

wide

range

of

applications.

The

Leq

meter

measures

Leq

in

ac-

cordance

with

ISO R 1

996

and

1

999

and

DIN

45

641.

The

sound

level

meter

complies

with

IEC

651

Type 1

(Imp.)*

It

provides

the

sound

analyst

and

noise

control

engineer

with

almost

everything

desirable

in

one

measur-

ing

instrument.

The

A-weighting

network

for

Leq

measurements

and

weighted

sound

measurements

are

built

in

together

with

a

linear

mode.

The

meter

response

may

be

switched

to

the

standardized

Slow,

Fast

and

Impulse

time

constants,

as

well

as

to

indicate

the

peak

value

of

the

measured

signal.

The

impulse

facility

gives

the

feature

of

being

able

to

measure

the

maximum

of

the

short

time

RMS

value

of

impul-

sive

sounds

with

time

weighting

in

accordance

with

IEC

651

Type 1

(Imp.).

The

peak

mode

allows

meas-

urement

of

signal

peaks

with

dura-

tion

as

short

as

50

f.J.S,

which

is

of

importance

when

determining

the

harmful

effect

of

impulsive

noise.

In

addition,

"Max.

Hold"

can be se-

lected

on

the

indicating

meter

for

all

time

constants

to

measure

the

maximum

sound

level

during,

for

ex-

ample,

an

aircraft

flyover

or

vehicle

pass-by

.

The

measuring

range

setting

is

displayed

in

windows

on

the

meter

scale

to

ease

reading

. A

liquid

crys-

tal

display

shows

L

eq,

SEL

or

altern-

atively

elapsed

time

.

The

measuring

period

may

be

preset

so

that

me3s-

urements

can be

automatically

* Type 1

instruments

of

IEC

651

{Imp.)

correspond

on

all

significant

points

to

the

earlier

standard

IEC 1

79

A and

to

DIN

45

633

2

stopped

.

The

display

is

very

easy

to

read

both

in

direct

sunlight

and

un-

der

low

ambient

light

conditions

.

An

overload

indicator

gives

warning

of

excessive

signal

levels.

To

allow

measurements

of

Leq

in

octave

and

third

octave

bands,

and

sound

analysis,

both

linear

and

A-

weighted,

the

instrument

is

equipped

with

in-

and

output

sock-

ets

for

connection

of

external

fil-

ters.

Two

analog

outputs

(AC

and

DC)

give

the

possibility

for

connec-

tion

of

level

recorders,

tape

recor-

ders

and

headphones

etc.

(sound

le-

vel only). A

built-in

reference

vol-

tage

provides

easy

electrical

calibra-

tion

of

both

the

Leq

-meter

and

sound

level

meter.

The

2218

is

powered

from

3,

1,5

V

alkaline

batteries

(IEC R

20,

D

cells)

giving

approximately

25

hours

of

continuous

operation.

Longer

operating

times

can

be

ob-

tained

using

an

external

DC

supply.

The

battery

condition

can

easily

be

checked

on

the

meter

.

As

a

very

valuable

feature

this

instrument

has

a

built-in

long-life

battery,

which

protects

the

memory

content

of

the

Leq

meter

if

power

fails,

or

batter-

ies

have

to

be

exchanged

during

the

measurement

.

Sound

Level

Measurements

As

standard,

the

instrument

is

equipped

with

a 8 & K

high

sensitiv-

ity, 1/

2"

diameter,

free-field

Con-

denser

Microphone

Type 41

65,

giv-

ing

it

a

measuring

range

from

25

dB

to

145

dB

and

a

wide

frequency

range,

both

in

free

and

diffuse

sound

fields,

due

to

its

excellent

om-

nidirectivity.

The

microphone

is

de-

livered

with

its

own

individual

cali-

bration

chart

giving

all

relevant

cali-

bration

data

and

complete

fre-

quency

response

curve

.

The

microphone

may

be

mounted

directly

on

the

instrument,

but

should

normally

be

mounted

on

the

Extension

Rod

UA

01

96,

which

is

included,

and

which,

together

with

the

conical

shaped

front-end

of

the

instrument

ensures

the

free-field

characteristics

required

to

fulfil

the

IEC, DIN

and

ANSI

requirements

for

precision

sound

level

meters.

If

it

is

desired

to

remove

the

microphone

even

further

·

from

the

instrument,

standard

Bruel

& Kjcer

microphone

Extension

Cables

are

available

in

lengths

of

3,

10

and

30

metres.

The

cables

are

inserted

between

the

removable

input

stage

and

the

Sound

Level

Meter

to

prevent

any

effect

of

cable

capacitance

on

cali-

bration.

A

windscreen,

which

should

be

fitted

over

the

microphone

when

measuring

outdoors

in

order

to

re-

duce

wind

noise,

is

included.

Also

included

is

an

input

adaptor,

to

be

fitted

instead

of

the

microphone,

al-

lowing

direct

electrical

input,

for

in-

stance

from

accelerometers

or

hy-

drophones

or

calibration

oscillators.

For

measurement

of

higher

levels

than

is

possible

with

the

1

/2"

microphone

Type

41

65,

or

if

a

lin-

ear

random

incidence

microphone

response

is

required,

other

1

/2"

microphones

from

the

8 & K

range

can

be

used

directly,

for

instance

Type

4133,4134

or

4166.

For

special

applications,

the

sound

level

meter

can

be

used

with

other

microphones

than

described

here,

and

the

Product

Data

Sheet

for

the

8 & K

microphone

range

should

be

consulted

.

See

also

the

survey

of

accessories

available

(Fig.6)

for

use

with

the

2218.

Leq

Measurements

The

measurement

of

Leq

is

based

~ig

.

1

.

2218

equipped

with

Integrator

ZR

0020

and

accelerometer

for

vibration

measurements

and

1

/3

Octave

Filter

Set

Type

1616

for

frequency

analysis

on

the

equal

energy

principle

where:

[ 1 JT ( P(t) ) 2 ]

Leq

= 10 log T 0 p

dt

0

P

0 is

the

reference

sound

pressure

(

20

JJPa),

P(t) is

the

time

varying

sound

pressure

measured

using

the

A-weighting

network

and

T is

the

time

interval

in

which

it

is

mea-

sured

.

From

these

values

Leq

is

cal-

culated

and

the

result

shown

on

a

3 1

/2-digit

liquid

crystal

display

with

a

resolution

of

0,1

dB.

Alterna-

tively,

the

display

also

shows

elapsed

time

with

a

maximum

reso-

lution

of

0,001

hour,

maximum

measuring

time

is 10 5

seconds

(27,7

hours).

The

measuring

period

can

be

preset

enabling

automatic

stop

of

measurement,

when

preset

time

has

elapsed;

this

means

that

the

instrument

can

be

left

unat-

tended

during

measurement

.

When

not

set

for

a

fixed

integra-

tion

period,

the

measurement

can

be

stopped

by

the

operator

at

any

time,

for

instance

at

the

completion

of

a

machine

operating

cycle.

Be-

cause

the

Leq

value

is

continuously

updated

during

the

measurement,

the

user

can

watch

the

level

of

non-

stationary

signals

converge

to

a

con-

stant

value.

For

data

like

traffic

noise,

the

operator

can

stop

the

test

when

a

steady

Leq

value

is

reached

.

The

221

8

shows

when

sufficient

data

have

been

acquired,

thereby

maximizing

accuracy

and

minimizing

measurement

time

.

The

221

8

also

has

provision

for

measuring

the

Sound

Exposure

Le-

vel, SEL

*,

which

is

defined

as

the

level

which,

if

maintained

constant

for

a

period

of

1

second,

would

cause

the

same

A-weighted

noise

energy

to

be

received

as is

actually

received

from

the

measured

noise

event

.

The

SEL is

used

to

describe

single

events

such

as

flyovers,

and

SEL = 10

log+

f

~

(

P~t)~

2

dt

ref

-~

0

where

r ref =1

second

See

also

: ISO/DIS

3891

Procedure

for

de-

scribing

aircraft

noise

heard

on

the

ground.

Note

:

SEL

has

previously

also

been

known

as

LAX .

To

avoid

any

possible

confusion

with

recently

suggested

U.S.

standards

for

sound

measurement

units

the

value

repre-

sented

by

the

above

equation

will

be

re-

ferred

to

exclusively

in

future

as

SEL.

Fig.2.

Pistonphone

Type

4220

and

Sound

Source

Type

4230

compare

them

in

order

to

assess

the

annoyance

they

cause

.

Vibration

Measurements

When

the

microphone

is

replaced

by

the

Integrator

ZR

0020

(Fig.1)

and

one

of

the

B & K

accelerome-

ters

is

connected,

the

instrument

functions

as a

vibration

meter

indi-

cating

vibration

velocity,

displace-

ment

or

acceleration.

A

calculation

disc

delivered

with

the

Integrator

makes

conversion

of

dB

reading

into

vibration

units

a

simple

matter.

Calibration

Acoustical

calibration,

which

also

tests

the

microphone,

can

easily

be

made

by

either

of

the

two

calibra-

tors

available:

Pistonphone

Type

4220,

which

gives

a SPL

of

1

24

dB

with

±

0,2

dB

accuracy

at

250Hz,

and

Sound

Level

Calibrator

Type

4230,

which

gives

a SPL

of

94

dB

with

±

0,25

dB

accuracy

at

1 kHz

(see

Fig.2).

When

using

the

sound

level

meter

for

vibration

measure-

ments,

complete

calibration

can

be

performed

by

means

of

the

Portable

Accelerometer

Calibrator

Type

4291,

which

calibrates

at

10

ms-2

peak

and

79,6

Hz.

·• ®

Fig.4.

Level

Recorder

Type

2306

and

Tape

Recorder

Type

7005/06

Audiometer

Calibration,

Hearing

Aid

Testing

When

the

microphone

is

replaced

by an

Artificial

Ear Type 41

52

or

41

53

with

Microphone

4144

or

41

34

respectively,

a

precise,

com-

pact

and

fully

portable

audiometer

calibrator

is

produced.

A

practical

carrying

case

KE

0055,

similar

to

that

shown

on

Fig.5,

with

provision

for

accessories

required

for

audi-

ometer

calibration

may

be

ordered

separately.

Frequency

Analysis

For

frequency

analysis

of

the

mea

-

sured

sound

or

vibration

level,

the

Octave

Filter

Set

Type 161 3 (Fig.3)

or

the

Third-Octave

Filter

Set

Type

161 6 (Fig .3)

attaches

directly

onto

the

sound

level

meter,

and

con-

nects

electrically

with

a

connection

bar

.

Type

161 3

contains

11

octave

filters

(with

adjustable

attenuation)

with

centre

frequencies

from

31,5

Hz

to

31,5

kHz. Type

1616

contains

34

third

octave

filters

with

centre

frequencies

from

20Hz

to

40kHz

.

Narrower

band

frequency

analysis,

as is

often

required

for

vi-

bration

analysis,

can

be

made

using

the

battery

powered

filters

:

Tunable

Filter

Type

1

621

or

Tracking

Filter

Type

1623

(Fig.3)

.

Fig.3.

Filters

Types

1613,

1616,

1621

and

1623

3

Field

Recording

When

measuring

in

the

field,

the

tedious

work

of

plotting

levels

by

hand

can be

completely

eliminated

by use

of

the

small,

portable,

bat-

tery

operated

Level Recorder Type

2306

(Fig.4)

or

the

portable

Two

Channel

Level

Recorder

Type

2309.

They

connect

via a

cable

to

the

out-

put

of

the

sound

level

meter

and

can

record

sound

levels

either

as

a

function

of

time

or,

if

the

sound

le-

vel

meter

is

equipped

with

a

filter,

as a

function

of

frequency

. For

time

recordings,

use

can

be

made

of

very

slow

recording

paper

speeds, so

that

diagrams

showing

sound

level

variations

over

longer

periods

of

time

can be

recorded

on

a

reason-

able

length

of

paper.

Such

charts

are

of

great

help

in

almost

any

type

of

noise

investigation

and

ease

the

location

of

noise

events

with

re-

spect

to

time

as

well

as

the

possible

source.

Frequency

spectrograms

can be recorded

directly

on

fre-

quency

calibrated

paper,

and

can be

made

semi-automatically

in

, a

few

minutes,

using

the

filters

Types

1613,

1616,

1621

and

1623.

The

recorded

spectrogram

and

time

his-

tories

provide

immediate

documenta-

tion

of

the

measurement

made

and

can be

inserted

directly

in

the

meas-

urement

report

. If

further

investiga-

tion

of

the

measured

signal

is re-

quired

back in

the

laboratory,

the

battery

operated,

portable

Tape Re-

.

corders

Types

7005

and

7006

(Fig.4)

should

be used.

Sound

Measurement

Sets

Two

Sound

Measurement

Sets

Type

3514

and

3515,

containing

the

most

commonly

used accesso-

ries,

have

been

assembled

in

the

practical

Carrying

Case KE

0055.

See

Fig.5.

The

sets

combine

com-

plete

portability

with

laboratory

ac-

curacy.

They

contain

:

Precision

Integrating

Sound

Level

Meter

with

standard

accessories

Octave

Filter

Set

(3514

only)

Third

Octave

Filter

Set

(351

5

only)

Microphone,

1I

2"

Pistonphone

Extension

Cable

Tripod

Adaptor

Nose

Cone,

1

/2"

Carrying

Case

4

2218

1613

1616

4166

4220

AO

0027

UA

0588

UA

0386

KE

0055

VIBRATION

MEASUREMENT t

a Accelerometers

Accelerometer ·

-

~

.

Calibrator lpI Typical : 4366, 4367, 4368,

4291

.ViiP.

4369, 4370, 4371

Artificial

AUDIOMETER

CALIBRATION

Artificial

Ear

Artificial

Ear Mastoid

•)

Microphone

Extension

Cable AO 0027 must ~

-

~ftij

"I

be

used

4153 4152

•930

1"

Wind Screen

DB

1021

.

UA

0207

~P...!Q!.

1---------

=----l

..LL.l§li

Control

Cable

1613-

A00183

1616-

A001B4

1621

-AQ 0034

1623 -AQ 0034

Level Recotde< \

rFf01

__

\_

__

l:=liJ

2306

Random

1"

-

1/2"

Two

Channel Level

Recorder

2309

In

cidence Corrector

1"

Mi

crophone

Adaptor

~

m

--.----L---0

SOUND MEASUREMENT

4220

UNDERWATER

SOUND MEASUREMENT

UA

0055

Nose Cone

UA

0387

UA

0355

Hydrophone

Type B100

Hydrophone

Type B103

4144

4145

1

"-

1/

2"

DB 0962

Flexible

Extension Rod

--...--,--r'-~

UA

0196

Connection Cable

AO 0116

Octave Filter

Set

1613

or

I

Third Octave

--.-l

FiherSet

I

1616 I

I

AO 0116 I

I

~a~~;,necliOn

ll

i

Tunable~

-

-1·~··-

I

Track~ng

I

~~~~r

~

-

- •

::.~

~~~~

-_

.J

Accessories included

with

2218

underlined

Fig

.

6.

Survey

of

Accessories

available

for

Type

2218

Accessories

A

wide

selection

of

accessory

equipment

is

available

to

expand

the

application

possibilities

of

this

Integrating

Sound

Level

Meter.

A

survey

showing

the

connection

pos-

sibilities

of

the

most

useful

items

is

given

in

Fig.6.

For

more

information

on

individual

instruments

and

trans-

ducers

shown,

please

ask

for

sepa-

rate

data

sheets

.

Fig.5.

Sound

Measurement

Set

Type

3515

Description

The

Precision

Integrating

Sound

Level

Meter

Type

221

8

contains

a

condenser

microphone,

a

remove-

able

input

preamplifier

stage,

an

am-

plifier

section

with

A-weighting

fil-

ter,

attenuator,

overload

indicator,

and

in-

and

outputs

for

external

fil-

ters.

This

is

followed

by an

auto-

ranging

attenuator,

and

a

logarith-

mic

RMS

detector

circuit

with

a

moving

coil

meter.

From

the

log.

converter

in

the

logarithmic

mean

square

(LMS)

detector,

a

signal

feeds

to

the

Leq

calculation

circuit

which

contains

counters

and

memo-

ries

for

noise

dose

and

time

and

a

display.

A

simplified

block

diagram

of

the

2218

is

shown

in

Fig.7.

Microphone

The

B & K

microphone

Type_

4165

employed

in

the

221

8,

is a

preci-

sion

condenser

microphone

.

It

is

de-

signed

to

have

a

linear

frequency

re-

sponse

for

free-field

sound

measure-

ments

and

0°

angle

of

incidence

(perpendicular

to

microphone

dia-

phragm).

The

microphone

has

excel-

lent

omnidirectional

characteristics

over

a

wide

frequency

range.

These

characteristics,

of

the

microphone

alone

and

of

the

complete

instru-

ment,

are

shown

in Figs. 13

and

14.

Figs.8

and

9

show

the

fre-

quency

response

curves

of

the

com-

plete

instrument

for

0°

incidence

sine

waves

and

in a

diffuse

field.

All

curves

are

well

within

the

re-

quirements

of

the

relevant

stan

~

dards.

A

calibration

chart

with

fre-

quency

response

curve

and

sensitiv-

ity

data

(individually

determined

for

each

microphone)

is

supplied

with

the

sound

level

meter.

The

micro-

phone

is

extremely

reliable

and

un-

affected

by

humidity

and

tempera-

ture

variations

over

a

wide

range.

The

diaphragm

is

quartz-coated

to

offer

protection

in

humid

and

corro-

sive

atmospheres

and

back

venting

allows

it

to

be used

with

the

Dehu-

midifier

UA

0308

for

further

protec-

tion

in

humid

environment

The

sen-

sitivity

of

the

microphone

is

typic-

ally

50

mV

/

Pa

(5

mV

/

J.Lbar)

with

a

polarization

voltage

of

200

volts

.

Input

Stage

The

removable

input

stage

has

an

extremely

high

input

impedance

to

match

the

high

impedance

of

mic-

rophones

and

accelerometers.

The

output

impedance

is

low

to

allow

ex-

tension

cables

to

be

inserted

be-

tween

input

stage

and

sound

level

meter.

Attenuator,

Weighting

Network

and

Overload

Indicator

Following

the

input

stage

is

the

A-

weighting

network

which

is

distrib-

uted

on

both

sides

of

the

RANGE

at-

tenuator;

a

switch

allows

selection

between

"A"

and

"Lin"

frequency

weighting

(see Fig.1 0).

The

attenua-

tor

has

three

ranges

each

shifted

20

dB

in

order

to

cover

the

full

mea-

suring

range

from

25

to

145

dB.

An

overload

indicator

monitors

the

input

signal

level

and

the

output

to

"Ext

.

Filter"

and

will

cause

a LED

lamp

to

flash

if

overload

occurs.

Be-

tween

the

two

following

amplifier

stages,

external

filters

can

be

in-

serted

providing

the

possibility

of

making

frequency

analyses,

even

on

A-weighted

signals.

An

AC

out-

put

from

the

last

amplifier

allows

connection

of

external

registration

equipment.

r::l

L:::J

Meter M

ode

Swi

tc

h

"T

o"

Ext. Filter

"From"

" A

C"

" Lowe

r"

" D

C"

O

utput

Fig.7.

Simplified

block

diagram

of

Type

2218

Autoranging

Attenuator

and

Detector

Circuit

The

signal

now

feeds

to

the

auto

-

ranging

attenuator

which

extends

the

dynamic

range

of

the

detector

circuit

(and L eq

calculation

circuit)

from

63

to

approximately

83

dB.

The

detector

which

is a

logarithmic

RMS

detector,

gives

true

RMS

de-

tection

.

It

has

the

three

standard-

ized

time

constants

"Slow",

"Fast"

and

"Impulse"

and

a

"Peak"

feature

. Fig .11

shows

the

response

of

the

detector

and

meter

to

tone

bursts

of

varying

duration.

"Fast"

and

"Slow"

responses are

mea-

sured

using

a

tone

burst

stepping

20

dB in

amplitude;

"Impulse"

re-

sponse is

measured

using

a

signal

stepping

from

0

V.

For

the

"Im-

pulse"

responses, 0 dB

corresponds

to

10 dB

and

35

dB

below

full

scale

deflection

of

the

meter

for

the

up-

per

and

the

lower

curve

respec-

tively.

At

the

upper

limit

of

the

dy-

namic

range

the

crest

factor

capabil-

ity

is 1

,4,

increasing

linearly

with

decreasing

signal

level

to

a

maxi-

mum

of

approximately

60.

DC

output

and

Meter

The

DC

output

from

the

detector

circuit

is

intended

for

use

with

level

recorders

and

provides

a DC

voltage

proportional

to

the

dB-value

of

the

measured

signal

with

the

full

dy-

namic

range,

80

dB,

of

the

sound

le-

vel

meter.

The

meter

covers

a

50

dB range

which

by

means

of

the

METER

RANGE

switch

can be

shifted

30

dB

to

cover

the

full

80

dB

range

of

_

the

detector

circuit.

The

measuring

range

is

displayed

in

windows

on

the

meter

scale

in

'accordance

with

the

setting

of

METER RANGE

switch

and

the

RANGE

attenuator,

in

order

to avoid reading

errors

. In

addition

to

the

normal

meter

read-

ing,

it is

possible

to

select

"Max.

Hold"

on all

the

time

constants

in

order

to

measure

the

maximum

le-

vel

which

occurred

during

the

meas-

urement

period.

Leq

Calculation

Circuit

The

previously

described

circuits

constitute

a

normal

precision

im-

pulse

sound

level

meter

with

anal-

ogue

display

and

can

be used

alone

as

such

. For

calculating

the

Leq

or

SEL a

signal

·

from

the

log

converter

(2

log e(t)) is fed via

the

antilog

con-

verter

to

an

integrator.

Here

it

is

converted

into

a

frequency

propor-

tional

to

the

squared

value

of

the

Note:

The

autoranging

facility

is locked

when

the

"Peak

"

mode

is

used

.

This

mode

should

therefore

be

selected

when

measuring

highly

impulsive

noise

, e.g.

gun

shots

.

5

measured

sound

pr~ssure

and

fed

to

a

counter

via a

gating

circuit

which

routes

the

signal

to

different

stages

of

the

counter

corresponding

to

the

state

of

the

autoranging

atten-

uator.

Since

integration

is

performed

by

analog

means

and

carried

out

di-

rectly

on

the

squared

signal,

it

is

in-

dependent

of

time

constants

and

crest

factor

limits

present

in

the

me-

ter

detector

.

Therefore

the

crest

fac-

tor

capability

is

high,

overload

being

the

only

limit.

Clock

Generator

and

Time

Counter

The

time

used

for

calculating

the

Leq

is

obtained

from

a

stable

clock

generator

with

a 1 Hz

output

via

the

time

counter.

The

data

from

this

and

the

dose

counter

feeds

to

the

calculation

circuit

where

Leq

or

SEL is

calculated

.

Calculation

Circuit

and

Display

This

circuit

is

preprogrammed

to

calculate

Leq

in

accordance

with

the

formula

given

previously.

The

output

from

the

circuit

feeds

to

the

display

via a

driver

circuit

.

The

measurement

result

is

displayed

on

a 1

/2",

3 1

/2-digit,

7

segment

liq-

uid

crystal

display,

the

resolution

of

which

is

0,1

dB.

The

result

is

up-

dated

with

intervals

of

about

one

second.

The SEL

calculation

is

performed

with

the

221

8 in

the

"Stand-by"

mode

by

resetting

the

time

counter

to

1 second by

means

of

the

SEL

button

and

then

from

the

content

of

the

time

and

dose

counter

the

calcu-

lation

circuit

now

calculates

SEL in

accordance

with

the

formula

given

previously

.

The

resuIt is

shown

on

the

display

with

0,1

dB

resolution.

Apart

from

Leq

and SEL,

the

dis-

play is

also

able

to

show

"Elapsed

Time".

The

display

mode

is

chosen

by

one

of

two

pushbutton

switches.

These

switches

are

also

used

to-

gether

to

preset

the

measurement

time.

When

the

preset

time

has

elapsed,

the

instrument

switches

to

stand-by,

indicated

by a

lamp.

Before

commencing

measure-

ments,

counters

for

time

and

dose

must

be reset;

this

is

performed

by

operating

the

two

L

eq

RESET

switches

simultaneously;

two

switches

are used

to

avoid

acciden-

tal reset.

6

dB

+6

+4

+2

0

-2

-4

-6

-8

-10

-12

10

I'..

......

~

lL'

20

100

200Hz

2

kHz

I

IEC

651

-

v

Type

1 -

-

........

'

\.

I

10

20

Frequency

760157

/ 1

Fig.8.

Free-field

frequency

response

of

the

complete

instrument

to

sine

waves

with

0°

inci-

dence

dB

+6

+4

+2

0

-2

-4

-6

-8

-10

-12

.......

,.,

10

+ 20

+ 10

co

"0

0

.

::

Q)

"'

c

-10

0

~

a:

-20

Q)

>

-

~

-30

a;

a:

-40

-50

-60

-70

.._

-

.,-

-

20

I I I L

I I I I

I

ANSI

S1

,4-

1,971r-

v

-

~

..

-

--"L

' ' l"l

~..,

\,.I

I

I'

100 200

Hz

2 kHz 10

20

Frequency

Jype

1

r-

760156

Fig.9.

Diffuse-field

frequency

response

of

complete

instrument

Lin

~

/

/A

/

v 2 5 2 5 2 5

10

4

Hz

2

Frequency

770834

Fig

.10 .

Frequency

response

of

the

2218

without

microphone

in

lin

and

A

mode

+2 Meter deflection (dB rei

to

continued signal level)

0

-2

-6

-8

-10

-12

.

~~

//'

//

~y

'/'

~

. .

'Impulse"

-14

-16

1 2 5

~,

...

~

.....

/

,.,

~

~lerance

/

v:

~

IEC "Impulse".,..

~

./

L

~

,/

~--"":'Fast"-

I'"

f I

"""

"Slow"

I'

I I

10 2 5

-

-v

/ /

Tolerance

/ IEC

"Fast'~

>-'

....

Tolerance

IEC

"Slow"

v

/

v

~

f =

2kHz

II

100 2 5 1000

Pulse

length t (ms)

Fig.11.

Response

of

rectifier

and

meter

to

tone

bursts

of

varying

duration

...-

--

170102

/ 1

Frequency

761150

Fig

.

12.

Maximum

permissible

input

voltage

with

different

lengths

of

extension

cables

at

input,

as a

function

of

fre-

quency

so.-

-.-.-.-rrr

nr--~

.--.--.-

......

_J

a..

(/)

al

"'0

70~~

-1

~-r~~~~

4-~r-r-r+~-H

100 200 1

kHz

770564

Fig.15.

Equivalent

sound

pressure

level

when

complete

sound

level

meter

is

excited

vertically

at

1

ms-2

80.--.-.-.-rrrnr--.-

~~~r-~

~~

_J

a..

(/)

al

"'0

70~-+

-4-+-H

~~~

+-1--1+

SPL produced

by

exciter

20Hz

50

100 1

kHz

770567

Fig

.

16.

Equivalent

sound

pressure

level

when

complete

sound

level

meter

is

excited

horizontally

at

1

ms-2

Because

the

attenuator

setting

en-

ters

into

the

calculation

of

Leq.

the

attenuator

must

not

be

operated

dur-

ing

measurement.

However.

if

oper-

ated

accidentally

the

display

will

flash

indicating

that

the

measuring

result

may

be

wrong.

The

display

continues

to

flash

until

the

instru-

ment

is reset. A

STAND-BY

switch

is also

provided

in

order

to

interrupt

measurement

without

resetting

the

counters.

"Stand-by"

mode

is

indi-

cated

by

a

lamp.

Fig.13.

Directional

characteristics

of

the

microphone

Type

4165

in

a

free

field

Fig.14.

Directional

characteristics

of

the

complete

instrument.

inclusive

microphone

and

exten-

sion

rod,

in

a

free

-

field

Power

Supply

Power

is

supplied

from

3

alkaline

batteries

(IEC R

20).

which

will

pro-

vide

approximately

25

hours

of

con-

tinuous

operation;

operating

times

of

approximately

20

hours

can be

obtained

using

rechargeable

NiCd

cells

.

When

required,

the

instru-

ment

can also be

operated

from

an

external

DC

supply

of

+ 4 V

to

+ 8 V

via a

7-pin

DIN socket. If

supply

vol-

tage

falls

below

the

lower

limit,

the

STAND-BY

lamp

will

light,

the

meas-

urement

will

stop,

and

a

built-in

long-life

battery

will

automatically

be

switched

on

to

protect

the

con-

tent

of

time

and

dose

counters.

This

important

feature

also

allows

the

ex-

change

of

batteries

without

losing

information,

provided

that

the

POWER

switch

is

"On".

Reference

Generator

For easy and

accurate

electrical

calibration

of

both

sound

level

me-

ter

circuit

and Leq

calculation

cir-

cuit,

a 1 kHz

reference

generator

is

built

in

.

7

Specifications

221

8

(Specifications

refer

to

2218

with

Extension

Rod

UA

0196

and

Microphone

4165

unless

otherwise

noted)

Measuring

Range:

Minimum

Level (dB)

Ext.

Filter

Type No.

Max

.

peak

level

(dB)

Weighting

Network

161

3 (Octave) 161 6 (1I 3 Octave)

A I

Lin

31.5-125

I

250-8000

1

16000

Hz

Hz Hz

20-1

600

I

2-20

I

Hz kHz Lin

145

25

I

38 30

I

25

I

32

25

I 3o I 35

Inherent

noise is

more

than

5 dB

below

stated

minimum

levels

Meter

Range:

Lower

Upper

Range

25

to

75dB

55

to

105

dB

25to105dB

45

to

95

dB

75

to

125

dB

45

to

125

dB

·

65

to

115

dB

95

to

145

dB

65

to

145

dB

Frequency

Response:

(Microphone)*

(0°

incidence,

free

-field)

± 1

dB:

4Hz

to

12

,5 kHz

± 2

dB

:

3Hz

to

20kHz

*)

individually

calibrated

(see also Figs.8

and

9)

Frequency

Response

:

(Amplifiers)

+ 1.

-3

dB:

10Hz

to 1 kHz

+ 1,

-1

,5 dB:

20Hz

to 1 kHz

+ 1, -

2,5

dB: 1 kHz to

20kHz

Frequency

Weighting

Network:

A-weighting

network

to

IEC

651

Input

Impedance

of

Input

Stage

ZC

0007:

> 1 GO

//<

0,5

pF

(typically

0,25

pF)

Maximum

Input

Voltage:

12,5

V RMS

(sinusoidal)

; see also Fig.

12

Overload

Indicator:

Indicate

overloads over

25

JlS

in

duration

AC

Output:

Output

Impedance:

<

25

0

Min.

load

Resistance:

2 kO

Nominal

Output

Voltage

: 3, 16 V

for

up-

per

limit

of

measuring

range

DC

Output:

Output

Impedance:

<

25

0

Min.

load

Resistance:

2 kO

Nominal

Output

Voltage:

-50

mV

/dB,

OV

for

lower

limit

of

measuring

range

External

Filter

Sockets:

To

Ext.

Filter:

Output

Impedance:

<

25

0

From

Ext.

Filter:

Input

Impedance

: 1

46

kO

Inherent

Noise:

(Referred

to

input)

linear

: max.

50

J1V

Curve

A:

max

.

9J1V

Detector:

Characteristic:

True

logarithmic

RMS

Dynamic

Range

:

80dB

(60dB

+

20dB

autorange)

(Autorange

locked in Peak

mode)

Crest

Factor

Capability:

1.4

at

upper

li-

mit

of

measuring

range (max.

145

dB

peak),

increasing

linearly

with

decrea-

sing signal.

Max

.

60

for

Sound Level -

max

. 1

000

for

Leq

Accuracy:

±

0,5

dB

for

crest

factors

up

to

20

±

1,5

dB

for

crest

factors

between

20

and

50

Time

Constants:

Fast:

125

ms

Slow

: 1 s

Impulse

:

35

ms

(2.9

dB/ s decay rate)

Peak:

50J1S

(automatic

reset

after

0,5

s)

Max.

Hold Facility

for

all

time

constants.

Decay Time > 10

min

/dB at

25

°C

Meter

Functions:

Display

of

SPL over a

50

dB range,

which

can be

shifted

30

dB by

means

of

METER RANGE

switch,

and

battery

check

leq

Calculation

Circuit

:

Range:

25

-

145

dB

in

three

ranges

Accuracy:

±

0,

5 dB

Display:

1/ 2" LCD, 7-

segment

, 3 1/ 2

digit

Display

Functions:

leq:

Resolution 0,1 dB;

result

updated

approx. once every second

SEl:

Resolution 0,1 dB

Preset

Time:

Up

to

27,7

hours; max. res-

olution:

0,001

hour

Elapsed

Time:

Up

to

27,7

hours

;

max.

resolution:

0,

001

hour

Microphone:

Type:

1/

2"

B & K

free-field

condenser

microphone

Type 41

65

Sensitivity:

Approx

.

50

mV

/

Pa

,

individu

-

ally

calibrated

Temp.

Coeff.

:

Approx

.

-0,01

dB

/°

C

Temp

. Range:

-50

to +

60

°C

long

Term

Stability:

1 dB/

300

years at

27

°C operating

temperature

(extrapo-

lated); 1 dB/ 1

00

hours

at 1

00

°C

operat

-

ing

temperature

Polarization

Voltage:

200V

Directional

Characteristics:

See Figs.13

and

14

Calibration:

Built-in

1kHz

generator

, accuracy

better

than±

0,2

dB

Reference

Conditions

for

Calibration

Validity:

Type

of

Sound

Field

: Free

Ref.

Direction

of

Incidence:

Perpendicu-

lar

to

microphone

diaphragm

Ref.

Sound

Pressure:

20

11Pa

Ref.

Sound

Pressure

level:

94

dB

Ref.

Frequency:

1 kHz

Ref.

Temperature:

20

°C

Ref.

Measurin~

Range:

65

to

145

dB

Absolute

Accuracy

at

Reference

Condi-

tions:

±

0,7

dB

Effect

of

Humidity:

<

0,

5 dB

from

0 to

90%

RH

provided no

condensation

occurs

Effect

of

Sound

Field:

At

least

60

dB

below

sensitivity

of

micro-

phone

4165

Effect

of

Ambient

Pressure:

Approx

.

-0,001

dB/

mbar

at

1013

mbar

Effect

of

Electrostatic

Field:

Negligible

with

microphone

grid

fitted

Effect

of

Magnetic

Field:

80

A/ m (1

0rsted)

at

50

Hz gives:

<

35

dB(Lin) or <

25

dB(A)

Effect

of

Temperature:

-1

0 to

50°C

(

14

to 1

22°F)

± 0,5 dB

Batteries:

3 x 1,5 V,

IEC

Type

LR

20

(B

& K

order

No. QB

0004)

Battery

life:

(Continuous

operation)

Approx

.

25

hours

with

alkaline

batteries

(B

& K

order

No. OB

0004)

Approx

.

20

hours

with

rechargeable

NiCd cells

(B

& K No. OB

0008

, 3 rqd.)

Recharging

from

Power

Supply Type

2808

or

Battery

Charger

ZG

0113

via

7-

DIN socket

Dimensions:

82x

120

x

540mm

(3,3

x

4,7x

21

,3 in)

(

330

mm

(13 in)

without

extension

rod)

Weight:

2,

7 kg

(6,61b)

incl.

batteries

Accessories

Included

:

1/

2"

Condenser

Microphone

Type

4165

Input

Stage

ZC

0007

Flexible

Extension

Rod

UA

0196

Input

Adaptor

JJ

2615

Windscreen

UA

0237

3

Alkaline

batteries

QB

0004

Screwdriver

QA

0001

4

Screened

plugs

JP

0006

1

7-pin

DIN

plug

JP

0703

Accessories

Available:

See

survey

on

page 4

2.

CONTROLS

Protection Grid

-------

Meter Mechanical Zero

Adjustment

-::--+--------•

Stand-by (Batt. Low)

Lamp

Leq

Switch

--:r-t-----._..--.._

Power On Switch

-::--+--·••

Stand-by Switch

-:::r--t--~

Ext.

Filter

Switch

--~+-J•

From

Ext

.

Filter

--=~--1.,_,.

To

Ext.

Filter

-------Microphone

--------

Extension Rod

UA

0196

_...,..

__

Range

Switch

Digital Display

(dB or Hours)

r-....,1!!1!!1!:----+--- Elapsed Time Switch

--+--

Batt. Check Switch

......;;~---!--

SE

L Switch

n

..

~--ir----

AC

Output

_____

......,.

__

Meter Function Switch

771029

/2

F1g.2.1. Front view

of

2

21

8

9

MICROPHONE:

PROTECTION GRID:

EXTENSION ROD

UA0196:

POWER ON

Switch:

BATI.

CHECK

Switch:

WEIGHTING NETWORK

Switch:

METER FUNCTION

Switch:

RANGE

Switch:

METER RANGE

Switch:

METER SCALE:

METER

MODE

:

10

Half-inch

condenser

microphone

Type

4165.

Protects

the

diaphragm

of

the

microphone

from

physical

damage.

This

grid

should

not

be

removed,

except

when

the

microphone

is

to

be

fit-

ted

with

a Nose Cone

or

Rain Cover,

or

for

inspection

of

the

dia-

phragm.

DO NOT TOUCH THE

DIAPHRAGM

WITH

ANY

OBJECT.

This

flexible

extension

rod

connects

the

microphone

to

the

sound

level

meter

at

a

sufficient

distance

that

the

influence

of

the

body

of

the

.

sound

level

meter

and

operator

on

the

sound

field

is

minimized.

This

extension

rod

must

be used in

order

for

the

instrument

to

conform

to

precision

standards.

IEC

651

Type 1 (Imp.)

(earlier

IEC

179)

.

If

a

Dehumidifier

UA

0308

is

used,

it

is placed

between

the

micro-

phone

and

the

extension

rod.

When

screwing

the

microphone,

extension

rod,

and

sound

level

meter

together,

only

light

finger

torque

should

be used.

Push-button

switch

for

turning

the

instrument

on.

When

in

"On"

posi-

tion

the

display

should

be

operating.

If

the

needle

deflection

is

below

the

BATI

.

indication

on

the

meter

scale

when

this

button

is pressed,

batteries

must

be

exchanged.

See

section

3.2.

2-position

slide

switch.

Position

"A"

selects

the

standardized

fre-

quency

weighting

network

for

the

subjective

indication

of

loudness.

Brüel & Kjær 2218 User manual

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