BRUEL & KJAER 1022 - Noise Measurements

BRUEL & KJAER 1022

60 pages

To Next Page

To Next Page

To Previous Page

To Previous Page

Loading...

vibrations

in

buildings,

machinery,

ships,

etc.,

can

be

measured.

In

Fig.

6.2a

a

layout

is

shown,

where

the

Type

3332

is

be

·

ing

used

to

automatically

record

vibration

measurements

taken

on

the

base

of

an

electrical

motor,

the

Spectrometer

allowing

an

analysis

of

the

vibrations

to

be

made.

The

output

from

the

Accelerometer

is

fed

via

the

Preamplifier

1606

to

the

CONDENSER

MICROPHONE

input

of

the

Spectrometer.

Information

on

the

calibration

of

the

arrangement

is

given

in

the

manual

for

the

Type

1606.

Fig.

6.2b.

shows

a

recording

of

the

vibrations

from

a

synchronous

motor

which

uses

a

50

c/s

mains

supply.

In

this

recording

a

50

dB

Range

Potentio-

meter

was

used

in

the

Level

Recorder,

0

dB

reference

being

equal

to

an

acceleration

of

25 cm/sec2.

Noise

Measurements.

Noise

within

factories,

offices,

cities,

airports,

etc.

varies

with

the

time

of

day.

Therefore

it

is a

firm

requirement

that

recordings

of

the

noise

should

be

carried

out

over

a

conside

·

rable

period

of

time

as

a

single

recording

taken

at

a

particular

instant

would

provide

incorrect

information.

Fig.

6.3

shows

a

recording

taken

of

the

noise

level

in

a

mechanical

work-

shop

over

a

selected

period

of

time

by

using

one

of

the

WeighHng

Networks

in

the

Spectrometer.

As

can

be

seen

the

noise

level

varies

considerably

with

time

and

a

reliable

analysis

cannot

be

obtained

by

only

taking

a

few

measurements.

It

is

therefore

necessary,

when

doing

such

a

test,

to

record

continuously

and

then

to

stat

·

istically

assess

the

final

re

·

sult.

To

measure,

analyse

and

record

such

noise

the

Spectrometer

+

Level

Recorder

(i.e.

the

receiving

part

of

the

AF

Response

and

Spectrum

Recorder

Type

3332)

in

combination

with

a B & K

Condenser

Microphone

can

be

used.

DD

D D

DD

D

DDD

D

ODD

O

DDOOOOOOOOOOOO

OO

OOODOO

O

DOOD

O

DOOO

OO

O O

llrll~]car+

·

-

"'

QP

0123

10

100

1000

• c l

....

C L;,.

/619H

Fig. 6.3. Recording

of

the

noise level

in

a

mechanical

workshop

over

a period

of

time.

fi3