Brüel & Kjær 1627 User manual
InstructionManual
lnfrasound and Ultrasound Filter Set Type 1627
lnfrll•
G1
•
Ga•
A Filter Set
to
make use
of
the extended
frequency range
of
the Modular Precision
Sound Level Meter Type 2231. Its six filter
networks
include
G1
and
G2
which allow
infrasound measurements (ISO/DIS 7196).
Measurements
of
audible sound in the pres-
ence
of
ultrasonic noise are possible with
filter
network
U (Audio) which complies with
IEC
TC
29-169/WG 16. The other filter net-
works
are:
U1,
a proposed weighting which
approximates the sensory perception of ul-
trasound; Ultra, a 12,5kHz high-pass filter;
Infra, a 20Hz low-pass filter; and Linear.
Type 1627 can also be fitted
to
the Sound
Level Meters Types 2230, 2233 and 2234,
but only a limited use can be obtained.
A special microphone adaptor is included to
extend the useful low frequency range of
the 1/2-inch Microphone Type 4155
or
4165
to
below 1
Hz.
Type 1627 snaps onto the
bottom
of
Sound Level Meter, forming a
self-contained lightweight instrument.
+
BrUel
&
Kjcer
lnfrasound and Ultrasound Filter Set Type 1627
From
serial no. 1177522
August
1985
CONTENTS
1. INTRODUCTION AND SPECIFICATIONS (PRODUCT DATA) .............................................................................. 1
2.
CONTROLS..................................................................................................................................................................3
3.
OPERATION .................................................................................................................................................................5
3.1. PRELIMINARY ........................................................................................................................5
3.2. POWER SUPPLY................................................
..
....................................................................5
Battery check..........................................................................................................................5
Battery replacement...............................................................................................................6
Mains Power Supply and Charger ZG 0254.......................................................................7
3.3. MEASUREMENT.....................................................................................................................7
General ....................................................................................................................................7
Instrumentation.......................................................................................................................8
Measurement..........................................................................................................................8
4.
APPENDIX ...................................................................................................................................................................9
5.
SERVICE AND REPAIR............................................................................................................................................
11
type 1627
lnfrasound and Ultrasound Filter Set
USES: FEATURES:
Filter Set
for
Sound Level Meter Type
2231
, (plus
limited use with Types 2230, 2233, and 2234) • lnfrasound filter networks
G1
and G2
in
accor-
dance with ISO/DIS 7196
• Measurement
of
sound in the infrasonic and ultra-
sonic frequency ranges • Audio frequency filter network with ultrasound
cut-off
in accordance with IEC TC 29-169/WG 16
• Measurement
of
infrasound levels weighted for
both auditory magnitude response and indirect
non-specific responses
• Three other filter networks; 20Hz lowpass filter,
12,5kHz highpass filter,
16kHz
ultrasound weight-
ing, plus Linear
• Measurement
of
the audible noise emitted by ul-
trasonic equipment
• Measurement
of
the ultrasonic disturbances gen-
erated by ultrasonic equipment
• Special adaptor which extends the useful low fre-
quency range
of
the standard microphone down
to
below
1Hz
The
Infrasound
and
Ultrasound
Fil-
ter
Set
Type
1627 is a lightweight fil-
ter
set
which enables
the
analysis
of
sound
in
the
infrasonic
and
ultrasonic
frequency ranges.
Its
primary
use is
with
Modular
Precision
Sound
Level
Meter
Type
2231.
Not
only does
this
Sound
Level
Meter
have
the
broad
linear
frequency range necessary for
infrasonic
and
ultrasonic
measure-
ments,
but
it
also enables
measure-
ments
with
long
integration
times.
The
fluctuating
nature
of
infrasound
means
that
accurate
measurements
can
only be
made
when
long averaging
times
are
used.
Filter
Set
Type
1627 also includes
Microphone
Adaptor
UC 5265.
The
adaptor
increases
the
size
of
the
cavity
behind
the
standard
Microphone
Type
4155 (or
Type
4165)
and
extends
its
useful low frequency response from
around
2-3Hz
down
to
below 1Hz.
The
upper
frequency
limit
of
the
Sound
Level
Meter
with
the
standard
microphone
is
approximately
20kHz,
but
measurements
in
the
ultrasound
range
are
possible
with
a
microphone
of
smaller
dimensions. Use
of
the
ljs
inch
(pressure response)
Microphone
Type
4138 gives
an
upper
frequency
limit
of
140kHz.
Long
term
exposure
to
high levels
of
noise
outside
the
audible
frequency
range
can
have
harmful
effects.
In-
creasing awareness
to
this
fact
is
just
now giving rise
to
international
mea-
surement
standards.
ISO/DIS
7196
BP0500-11
Infrasound
and
Ultrasound Filter
Set
Type
1627 makes use
of
the
extended
frequency range
of
the
Modular Preci-
sion Sound Level
Meter
Type
2231.
Its
six filter networks (plus Lin.) enable a
variety of measurements in
the
infra-
sonic
and
ultrasonic frequency ranges,
including measurements according
to
ISO/DIS 7196
and
the
proposed IEC
TC
29
-169/WG 16. Microphone Adap-
tor
Type
UC 5265, which is included
with
the
filter set, extends
its
useful
frequency range down
to
below
1Hz.
Type 1627 snaps onto
the
bottom
of
Sound Level
Meter
Type
2231, forming
a self-contained lightweight
instrument
which is eminently suitable for
both
field
and
laboratory work.
concerns
itself
with
methods
for de-
scribing
infrasound
and
proposes two
frequency weighting curves
in
the
in-
frasonic region: G1
and
G2. G1
weighting
approximates
threshold
and
direct
(auditory
magnitude)
percep-
tion; G2 weighting is
proposed
for
the
assessment
of
non-specific reactions.
A
recent
IEC
draft
standard
(TC
29-169/WG
16) describes
the
characteristics
of
filters for
the
mea-
surement
of
audible
noise
emitted
by
ultrasonic
equipment.
Measurements
according
to
each
of
these
standards
may
now be
made
with
the
Type
1627
Filter
Set
together
with
the
Sound
Level
Meter
Type
2231 or, for
IEC
TC
29-169/WG
16,
with
Type
2230,
2233,
or
2234.
Type
1627
contains
6 filter
networks
plus
a linear (All
Pass)
setting.
The
BrGel&
Kjaer
Type
1627
FiltM/
Weightiog
lnfre•
Q1.
G2 •
lnfrasound and Ultrasound
filter
Set
characteristics
of
the
filter networks
are
shown graphically in Fig.
2.
The
filter
settings
are
as follows:
Lin
A
linear
or "All
Pass"
setting which
effectively by-passes
the
Filter
Set.
Ul
A
proposed
ultrasound
weighting
which
approximates
the
perceptory
response
to
sound
above
20kHz.
The
slope
of
the
weighting curve
at
20kHz
leads
to
a
smooth
transition
between
it
and
the
A
and
C weighting curves.
This
is
important
since
many
practical
ultrasound
sources
operate
between
15kHz
and
30kHz.
The
peak
in
the
weighting curve occurs
at
16kHz.
Be-
low
this
frequency
the
drop-off is
Fig.
1.
Sound
Level Meter
Type
2231
with
Infrasound
and
Ultrasound Filter
Set
Type
1627
18dB
per
octave; above
this
the
curve
falls away
at
a slope
of
6
dB
per
oc-
tave.
Ultra
A 12,5
kHz
highpass filter which al-
lows
measurements
in
the
ultrasound
frequency range
with
no weighting.
Such
a filter
may
be
required
when
an
evaluation
of
an
ultrasonic
sound
field
is
required
but
no
account
of
the
sub-
jective response
need
be
taken.
U
(Audio)
The
U filter
network
provides
band-
pass filtering
in
the
frequency range
10Hz
to
12,5kHz.
This
is
in
accor-
Frequency Range:
Selective
1
Hz
to
200kHz
Linear
1Hz
to
200kHz
(-
3dB)
Filters:
U1
:
16kHz
Ultrasound
Weighting
Ultra
: 12,5
kHz
Highpass
Filter
U
(Audio):
U
Weighting
ace.
to
IEC
TC
29-169/WG16
(10Hz
to
12,5kHz
bandpass)
Infra
:
20Hz
Lowpass
Filter
G1, G2 :
20Hz
lnfrasound
Wejghtings
ace.
to
ISO/DIS
7196
Attenuation
at
Reference Frequencies:
(i.e.
10Hz,
1kHz,
or
63kHz):
OdB
=O,SdB
Input Impedance:
10
kn
in
series
with
6,8~-tF
Input
Terminating
Impedance:
~1
00
n
dance
with
the
IEC
draft
standard
TC
29-169/WG
16.
Its
intent
is
to
en-
sure
that
measurements
of
sound
lev-
els
in
the
audible range
are
not
dis-
turbed
by
sound
levels
in
the
ultrason-
ic range.
Infra
A
20Hz
lowpass filter which allows
measurements
in
the
infrasound
fre-
quency
range
with
no
weighting.
The
weighting curve is
linear
down
to
about
1Hz.
Gl
An infrasonic frequency weighting
curve
proposed
in
ISO/DIS
7196
which
approximates
direct
human
perception.
The
peak
in
the
weighting
curve occurs
at
20Hz.
Below
this
fre-
quency
the
curve falls away
at
a slope
of
12
dB
per
octave down
to
1Hz
and
thereafter
18
dB
per
octave; above
20Hz
the
drop-off
is
24
dB
per
octave.
G2
Also
proposed
in
ISO/DIS
7196,
this
is
an
infrasound
weighting curve
which
accounts
for non-specific reac-
tions
and
indirect
effects.
Here
the
perception
mechanism
is
non-direct
and
is less
dependent
on
the
frequen-
cy
of
the
infrasound.
The
peak
in
the
weighting curve occurs
at
20Hz.
Below
this
frequency
the
curve falls away
at
a slope
of
6
dB
per
octave down
to
1
Hz
and
thereafter
12
dB
per
octave; above
20Hz
the
drop-off
is
24
dB
per
octave.
The
active filters
contained
in
the
Filter
Set
are
powered from
the
Sound
Level
Meter
through
the
15
pin
con-
nector,
provided
the
EXT.
FILTER
switch
on
the
Sound
Level
Meter
is
set
to
"In".
The
battery
pack
in
the
Filter
Set
contains
4 cells
IEC
LR
6
(B&K
No. QB 0013)
and
is always
connected
in
parallel
with
the
battery
pack
in
the
Sound
Level
Meter.
The
battery
life (alkaline cells) of
the
Sound
Level
Meter/Filter
Set
is
ap-
proximately
8 hours.
U(Audio)
2
10
20
50 100 1k 2k
Sk
10k 20k 50k 100k 200k
Frequency (Hz)
841768
Fig.
2.
Filter characteristics
of
the Filter
Set
Type
1627
Specifications 1627
Input Voltage:
Max
. 2 V RMS (2,8V
Peak)
Output Impedance: < 5 n
Output
Terminating
Impedance:
.,10kn
in
parallel
with
100
pF
Inherent Noise:
Lin, U1,
Ultra
:250~-tV
max.
U
(Audio),
Infra,
G1, G2 :200
~tV
max.
Magnetic
Sensitivity (50 Hz):
Approximately
1
mV
output
for
100
Aim
field
strength
Operating Temperature:
-10
to
+ 50°C
(+
14
to
+122°F)
Storage Temperature:
-20
to
+50°C
(-4
to
+122°F),
Batteries
Removed
Influence of
Temperature
on Attenuation:
< 0,5
dB
(-
10
to
+50°C)
Influence of Humidity on Attenuation:
< 0,5
dB
for
0
to
90%
relative
humidity
at
~
40°C
without
condensation
Batteries: 4 x 1,5 V IEC
Type
LR6
(QB 0013).
Batteries
used
as
extra
supply
for
SLM
Dimensions:
Length
105
mm
(4,1 in) -
Width
85
mm
(3,3
in)-
Height
47
mm
(1
,8 in)
Weight: 450 g
(1
lb)
including
batteries
ACCESSORIES INCLUDED:
Cells
(X4)
.................................................QB 0013
Low
Frequency
Microphone
Adaptor
.................
..
....
..
..
......................... UC 5265
Filter/Weighting:
Connector:
2.
CONTROLS
BrO
ei&K
j
ee
r
Type
1627
Fitt
er
/
Weighting
lnfnl
•
G1 •
G2 •
lnfrasound and Vltrasound
Filter
Set
Fig.
2.
1.
Front
view
of
the
Filter
Set
Type 1627
Cursor
for
selection
of
the following filter characteristics (see also
Fig.1 page
2):
"Lin." ("All-Pass") effectively by-passes the Filter Set.
"U1" a proposed weighting which approximates the sensory percep-
tion
of
ultrasound.
"Ultra" high-pass filter
for
ultrasound measurements with lower
limit-
ing frequency
of
12,5kHz.
"U(Audio)" complies with IEC
TC
29-169/WG
16,
and allows measure-
ment
of
audible sound in the presence
of
ultrasonic noise.
"Infra" low-pass filter
for
infrasound measurements with upper limiting
frequency
of
20Hz
"G1" in accordance with ISO/DIS 7196.
G1
weighting approximates
threshold and
direct
perception
for
infrasound measurements.
"G2" in accordance with ISO/DIS 7196. G2 weighting is proposed
for
the assessment
of
non-specific reaction
to
infrasound.
15-pin
connector
for
directly coupling the Filter Set Type 1627 to the
Sound Level Meters Types 2230, 2231, 2233 and 2234. This connector
ensures signal connection, plus interconnects the Filter Set and Sound
3
Level Meter batteries
for
powering the Filter Set only when Ext. Filter
"In"
mode on the Sound Level
Meter
is selected.
To
fit
the Filter Set,
remove the protective plastic cover from the
bottom
of
the Sound Lev-
el
Meter.
From
Ext.
Not
Not
Signal
To
Ext.
Filter
-
11
V
OV
used
+11
V
used
ground
Filter
80008008
8888800
Not
used
ov
+5V +Batt. - Batt. Power
-5V
On/Off
830457
11
Fig. 2.2. 15
pin
connector
of
the
lnfrasound
and
Ultrasound Filter
Set
Type 1627
Latches:
Battery Drawer:
Microphone Adaptor UC
5265:
Two latches
for
securing the Filter Set
to
the Sound Level Meter.
Battery
drawer
which accepts
four
1
,5
V alkaline cells (IEC type LR6,
AA
size). These are connected in parallel with the batteries in the
Sound Level Meter which supplies
power
to the Filter Set (see section
3.2). If desired the
battery
drawer may be replaced by one fitted with
rechargeable cells, such as that obtained with the Mains Power Supply
and Charger ZG 0254 (optional extra).
Screw-fit
adaptor
for
extending the lower limiting frequency
of
B& K
1f2-inch microphones. When used with Microphones Types 4155
or
4165 a lower limiting frequency
of
less than 1Hz is obtained. When
mounted, this
Adaptor
results in a 0,4 dB attenuation in the input stage
which must be compensated
for
when calibrating the Sound Level Me-
ter; i.e. when using the internal reference signal, the Sound Level Me-
ter
must be calibrated
to
94
dB+
K0 + 0,4 dB.
Fig. 2.3.
Microphone
Adaptor
UC5265
for
low
frequency measurements
4
3. OPERATION
3.1. PRELIMINARY
The lnfrasound and Ultrasound Filter Set Type 1627 and the Sound Level Meters Type
2230, 2231, 2233
or
2234 have matching 15-pin push-fit
connectors
which facilitate
direct
coupling
of
the instruments
to
form one compact unit. (See Fig.3.1
).
To
attach the Filter
Set
to
the Sound Level Meter, press the two side-latches and engage the connectors
using a gentle steady pressure
to
push the Filter Set and Sound Level Meter together.
When correctly secured with the Sound Level Meter, the
two
side latches should return
to their outer position.
Fig.
3.
1.
Filter
Set
with the
Sound
Level
Meter
Type 2231
3.2.
POWER
SUPPLY
3.2.1. Battery Check
The Filter Set is powered via the particular Sound Level
Meter
connected. The batteries
contained in the Filter Set are not used to power the Filter Set directly, but to increase
the
capacity
of
the Sound Level Meter's power supply. When using the Filter Set with
Sound Level Meter Type
2231
and alkaline batteries are
fitted
in both instruments, the
battery
life is approximately 8 hours.
5
..
.....
--~
-
~~~
-
-~.
'
Fig. 3.2.
Mounting
the Filter
Set
on
the
Sound
Level
Meter
Type 2231
To
check the battery level
of
the Filter Set, connect the Filter Set
to
the Sound Level
Meter
and remove the battery drawer from the Sound Level Meter. Switch on the Sound
Level Meter and check the
battery
condition
indicated on its display (See Sound Level
Meter
Instruction Manual). If a battery
"low"
indication is given, the batteries should be
replaced.
Note: One set
of
batteries, either in the Sound Level Meter
or
in the Filter Set, is
sufficient
for powering both instruments. However, the
battery
life is
of
course reduced.
For long term storage, it
is
recommended that the batteries are removed
to
conserve
their life time and as a general safety precaution.
3.2.2. Battery Replacement
6
Unlock the battery drawer and pull it out. Remove the deplenished batteries and place
four
new ones with polarities as shown in the
battery
drawer. Push the drawer
back
into
place until the lock is secured.
Fig. 3.3.
Battery
replacement
3.2.3. Mains Power Supply and Charger
ZG
0254 (option)
The battery drawer
of
the
ZG
0254,
containing 4 rechargeable cells,
fits
into the Filter
Set Type 1627 and can be recharged either in or outside the instrument via the socket
on the side. The Charger delivers enough current for simultaneously powering the Filter
Set and Sound Level Meter and recharging the cells to which the charger is attached.
When only recharging the cells {drawer pulled out
or
instrument switched off), a recharg-
ing cycle takes approximately 5 hours. When recharging cells while powering the instru-
ment, the recharging time is
of
course longer.
Note: It is not necessary for both battery sets, in the Sound Level Meter and in the Filter
Set, to be rechargeable.
To
avoid confusion, however, only
battery
drawers equipped
with rechargeable cells have the socket receiving the charger. If both instruments con-
tain rechargeable cells, it is necessary to use a separate battery charger with each
instrument.
Fig.
3.4.
Mains Supply
and
Charger
3.3. MEASUREMENT
3.3.1. General
In
the following sections emphasis is placed
on
the practical aspects
of
making infra-
sound
or
ultrasound measurements with a Sound Level Meter and the Filter Set Type
1627. For a comprehensive description of the philosophy and reasons
for
infra
or
ultra-
sound measurements consult the relevant standards and the various publicatio.ns on this
subject.
To
include the Filter Set in the measurement chain set the Ext. Filter switch on the
·Sound Level Meter to
"In".
The signal measured with the Sound Level Meter is then
filtered
or
weighted according
to
the position of the Filter/Weighting switch
on
the Filter
Set.
7
3.3.2. Instrumentation
Before attempting any measurement a basic but
important
rule is to make sure that the
frequency range
of
interest is covered by every item in the measuring chain, i.e. the
Microphone, the Sound Level Meter, the Sound Level Meter weighting (if any) and finally
the Filter Set itself.
If the frequency range
of
the Sound Level Meter microphone does
not
cover the fre-
quency span of interest, a different microphone should be selected. For example,
for
ultrasound measurements, the 1/4" Microphone Type 4135
(4
Hz-100 kHz, ± 2dB) with
Adaptor
UA 0035 can be fitted
to
the Sound Level Meter Type 2231; and
for
infrasound
measurements, the frequency range
of
the Microphones Type 4155
or
4165 can be
ex-
tended downwards (to less than 1 Hz) by use
of
the supplied Microphone
Adaptor
UC
5265.
For making a measurement
it
is then
just
necessary to check that the frequency
of
interest is contained in the Sound Level Meter frequency range, and that the
"Lin."
(All-
pass) frequency weighting
is
used.
Note:
-If a non-standard microphone is selected, remember to use the "Frontal" setting on
the Sound Level Meter,
as
the "Random" frequency correction is
not
valid
for
any
mi-
crophone.
-When mounted, the Adaptor
UC
5265 results in a 0,4 dB attenuation in the
input
stage
which must be compensated
for
when calibrating the Sound Level Meter; i.e. when using
the internal reference signal, the Sound Level Meter must be calibrated to
94dB
+ K0 +0,4dB.
3.3.3. Measurement
8
Proceed as for a normal measurement with
an
external filter, i.e. with Ext. Filter set to
"In". The measured sound pressure level is displayed by the Sound Level Meter.
For low frequency measurements long integration times must be allowed. When measur-
ing
with
an
Integrating Sound Level Meter, these can be obtained by use
of
the
Leq
measurement function (see Sound Level Meter Instruction Manual). As a rough guide, the
integration time can be defined as the
time
needed
for
the displayed value to stabilize. A
minimum integration time of 8 seconds (i.e.
an
8 seconds
Leq)
is recommended, although
for
very
low frequencies this value can be as high as
60
seconds
or
even more.
For high frequency measurements no special precaution are needed concerning the
integration time. However, care must be taken
to
avoid introducing reflections (e.g. from
body
of
the operator) which can have a marked effect on the accuracy
of
the measure-
ment, especially at high frequencies.
4.
APPENDIX
Lin
U1
Ultra
Audio
Infra
G1
G2
32 dB 23
dB
28
dB
17
dB
27 dB
21
dB
19
dB
T00843GBO
Table 4.1. Inherent noise level
of
2231 with 1627
10 100
500Hz
851152
Fig. 4.1.
Input/Output
phase
shift
with "U1" Filter
<Po
+270
+180
+90
0
-90
-180
-270
-360
10
100
cp
o
90
0
-90
-180
-270
-360
-450
1k 1 k 100k Hz
851154
Fig.
4.2.
Input/Output
phase
shift
with
"Ultra"
Filter
1k
10k Hz
851157
Fig. 4.3.
Input/Output
phase
shift
with
"Audio"
Filter
9
10
cpo
0
-
90
180
27
-338L------r------.------..--i~l
1 10 100 400 Hz
851156
Fig. 4.4. Input/Output phase
shift
with "Infra" Filter
10
cpo
+180
+90
0
-90
r180
-270
-360
2
10
20
40
100 500Hz
85
11
55
Fig.
4.5.
Input/Output
phase
shift
with "G1" Filter
100 Hz
85
11
53
Fig.
4.6.
Input/Output
phase
shift
with "G2" Filter
5.
SERVICE AND
REPAIR
The Type 1627 is designed and constructed to provide the user with many years of
reliable operation. However, should a fault occur which impairs its
correct
function, then
its internal batteries should be removed to prevent risk
of
further damage. For repair
consult the separate Service Instruction Manual available
for
the Type 1627
or
contact
your local 8 & K service representative. Under no circumstances should repair be at-
tempted by persons not qualified
in
the service of electronic instrumentation.
11
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