BRUEL & KJAER 2209 User guide

Impulse Precision Sound
Level Meter Type 2209
A compact and portable instrument
for precision sound and vibration
measur·ements. It conforms to IEC 179
for Precision Sound Level Meters,
the proposed IEC Recommendation
for Impulse Precision Sound Level
Meters and to DIN 45 633 parts 1
and
2.

BROEL & KJA:R instruments cover the whole field of sound and vibration
measurements.
The main groups are:
ACOUSTICAL MEASUREMENTS
Condenser Microphones
Piezoelectric Microphones
Microphone Preamplifiers
Sound Level Meters
Precision Sound Level Meters
Impulse Sound Level Meters
Standing Wave Apparatus
Noise
Limit Indicators
Microphone Calibrators
ACOUSTICAL RESPONSE TESTING
Beat Frequency Oscillators
Random Noise Generators
Sine-Random Generators
Artificial Voices
Artificial Ears
Artificial Mastoids
Hearing
Aid Test Boxes
Audiometer Calibrators
Telephone Measuring Equipment
Audio Reproduction Test Equipment
Tapping Machines
Turntables
VIBRATION MEASUREMENTS
Accelerometers
Force Transducers
Impedance Heads
Accelerometer Preamplifiers
Vibration Meters
Accelerometer Calibrators
Magnetic Transducers
Capacitive Transducers
Complex Modulus Apparatus
VIBRATION TESTING
Exciter Controls -Sine
Exciter Controls -Sine -Random
Exciter Equalizers, Random or Shock
Exciters
Power
Amplifiers
Programmer Units
Stroboscopes
STRAIN MEASUREMENTS
Strain Gauge Apparatus
Multi-point Panels
Automatic Selectors
MEASUREMENT AND ANALYSIS
Voltmeters and Ohmmeters
Deviation Bridges
Measuring
Amplifiers
Band-Pass Filter Sets
Frequency Analyzers
Real Time Analyzers
Heterodyne Filters and Analyzers
Psophometer Filters
Statistical
Distribution Analyzers
RECORDING
Level Recorders
Frequency Response Tracers
Tape Recorders
DIGITAL EQUIPMENT
Digital Encoder
Digital Clock
Computers
Tape Punchers
Tape Readers
IBRUEL&K\..14:-R
DK-2850 Nmrum, Denmark. Teleph.: (01) 80 05 00. Cable: BRUKJA, Copenhagen. Telex: 15316
+ ·
Impulse Precision Sound
Level Meter Type 2209
A compact and portable instrument
for precision sound and vibration
measur·ements. It conforms to IEC 179
for Precision Sound Level Meters,
the proposed IEC Recommendation
for Impulse Precision Sound Level
Meters and to
DIN 45 633 parts 1
and 2.

\
IMPULSE PRECISION
. SOUND LEVEL_ METER
TYPE 2209
From serial no. 934190
Revision June 1981

CONTENTS
1. INTRODUCTION AND SPECIFICATIONS (PRODUCT DATA) ................................................. 1
2.
CONTROLS ........................................................................................................ · .................. 9
3. OPERATION ..... ........ . ........................................................................................................... 14
3.1. INTRODUCTION ............ ..... ......................... . ................. ... ........ ...... ......... 14
3.2. PRELIMINARIES ................................................... . .................................. 14
Battery Considerations ......................................................... .. ..... ............. 14
Selection of Lower Limiting Frequency ....................................................... 15
Mounting the Microphone ............................................... ........ ................. 15
3.3. CALIBRATION FOR SOUND MEASUREMENTS ............................................ 16
General ........... . ....... .. .......... ....... ....... .... .. ............ . .................................. 16
Acoustical Calibration (External Source) ...... ............................................... 16
Calibration using Internal Reference Voltage .............................................. 18
3.4. SOUND MEASUREMENTS
................ ........ ................................................ 18
General .............. ....... ... .................... . .......... · ........ ..... ...... .. .... .. .... ............ 18
Procedure for Sound Measurements ...................... ............................ ..... ... 19
3.5. CALIBRATION FOR VIBRATION MEASUREMENTS ....................................... 20
General ..... .......... ..... ........ .......... ....... .. .......... ........ . .. ...... ............ .......... .. 20
Calibration using Accelerometer Calibrator Type 4291 -
direct reading in vibration units ...... .... ....... ...... .................................. ...... .. 21
Calibration using Internal Reference Voltage -
direct reading in vibration units .. ........ ................... .......... ....................... ... 22
Calibration using Accelerometer Calibrator Type 4291 -
meter reading in dB ..................................... .............. ............ .. .... ............ 23
Calibration using Internal Reference Voltage -
meter reading in dB ................................................................................. 24
3.6. VIBRATION MEASUREMENTS .................................................................. 25
General ...... ....... .. ... .......... ........... ....... ...... .............. . ...... .. .......... .. . ....... . .. 25
Procedure for Vibration Measurements ..................... . ........ .. .............. .. ...... 25
3.7. CONVERSION OF RESULTS IN dB TO VIBRATION UNITS ........... .......... .. ...... 26
With 4291 Calibration, Without Integrator ................................................. 26
With 4291 Calibration, With Integrator ZR 0020 ........................................ 28
With Internal Calibration, Without Integrator .............................. .... ............ 29
With Internal Calibration, With Integrator ZR 0020 ..................................... 29
3.8. VOLTAGE CALIBRATION ................... ... ........................ .......... ............. ... .. 29
3.9. VOLTAGE MEASUREMENTS .................................................................... 30
4. SPECIAL CHARACTERISTICS ............................. . ................................................................. 31
4.1 . GENERAL
.. ........ .......... . ...... ..... ................. ........... ................................ ... 31

4.2 . IMPULSE DETECTOR ...... .... .. .... .. ............ .. ...................... ...... ...... .. .. ...... ... 31
4.3. PEAK DETECTOR .. .. .. .. ...... .. .... .. .. .. .. .. .. .. ........ .. .. .. ............ .. ........ .. .... ...... .. 32
4.4. HOLD CIRCUIT . ..... ... .. ... .. .. ..... ..... . ............... .. .... ... ......... ... .. .... ..... .. .......... 33
4.5. CREST-FACTOR CAPABILITIES .... .. .... .. .. ............................................ .. ..... 33
4.6 . INPUT CAPACITANCE .. .. .. .. .. .............. .. .......... .............. .. ........ ........ .......... 35
4.7. INPUT-STAGE CONNECTIONS .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 35
5. ACCESSORIES ..................................... . ................................................ .. ................... ........ 36
6. USE WITH OTHER INSTRUMENTS ...................................................................................... 37
6.1. GENERAL ........ ... .. ...... .... .. .. .. . ..... .......... ............ . ....... . ..... ... . ..... . ..... .. ....... 37
6.2. LEVEL RECORDERS .. .. ...... . .. .. .. .. .. ...... ........ .. .. ................ ........... ............... 37
AC Recording ......... .. .. .. .. .......... . .. ............ ...... .. ..... ...... ..... ....... ......... ..... . .. 37
DC Recording ..... . .. ..... . ........ .. .. . ............. ......... ............. .. ..... .. ......... .......... 37
6.3. TAPE RECORDERS .... ........... .... .. . ...... ................. ...... ............. . ...... ...... ..... 39
6.4. DIGITAL RECORDERS ...... .. .......... ........ .. ..... ........... . ............ .. .. ... .. ............ 39

FEATURES:
• Complies with IEC
standard 651 Type 1
(Imp.)* and ANSI S1 .4-
1971 Type 1
• RMS detector for signal
crest factors up to 40
• Impulse detector with
Max. RMS Hold facility
• Peak detector with 20 JiS
rise time and Hold facility
• "0", "A", "B" and "C"
frequency weighting, plus
"Lin" response
• 2 Hz or 10 Hz selectable
low frequency cut-off
• Linear amplifier to 70kHz
• Plug-in preamplifier
• System overload indicators
• AC and DC outputs
• Individually calibrated,
high sensitivity, precision
condenser microphone
• Interchangeable meter and
attenuator scales to
facilitate direct reading in
sound and vibration units
• Wide selection of
accessories
USES:
•
Product noise reduction
and noise emission
certification
• Evaluation of hearing loss
risk
due to impulse noise
The Impulse Precision Sound level
Meter Type 2209 is the best avail-
able analog
instrument, featuring A,
B, C, 0-weighting, provision for use
with external filters, impulse and
peak measurement capability, and
in-
terchangeable meter scales for true
flexibility. The impulse and peak mea-
suring abilities assure accurate mea-
surement of signals such as exhaust
noise and repetitive impulses
which
have a high peak value compared to
their RMS level. The Type 2209 can
measure
with either "Impulse" or
with peak hold to suit the various dif-
ferent national standards. The wide
frequency range of the 2209 gives
the option of being used with many
different microphones over the fre-
quency range from infrasonic to ultra-
sonic sound.
The Type
2209 fulfils IEC 651 Type
1 (Imp.)* and ANSI S
1.4-1971 Type
1,
allowing the user to perform a
very
wide variety of acoustic and vi-
bration measurements.
• Performs as Octave,
Third octave or narrow
band analyzer with system-
matching filter sets
• Performs as Vibration
Meter or Analyzer with
appropriate accessories
•
Measurement of noise
having high peak values
• Infrasonic and ultrasonic
measurements
• Community, industrial and
architectural
measurements
• Measurement of shock,
vibration and blast noise
* IEC 651 supersedes the earlier IEC recommendations
123, 179 and 179 A • Audiometer Calibration
114-81
type 2209
Impulse Precision
Sound Level Meter
+ Ty.,.2209

Noise Measurements
The Impulse Precision Sound Le-
vel Meter Type 2209 meets the re-
quirements of IEC 651 Type 1 *,
DIN 45 633 part 1 and ANSI S.1 .4-
1 971 Type 1 for precision sound le-
vel
meters, as well as IEC 651 Type
1 (Imp.)* and DIN
45 633 part 2 for
impulse precision sound level me-
ters .
The 2209 is supplied with a high
sensitivity, 112 inch Condenser Mic-
rophone Type 4165, complete with
individual calibration chart and fre-
quency response curve. The 4165
provides a measuring range from
24 to 1 40 dB(A), as well as a wide
frequency range in both free and dif-
fuse sound fields, because of its ex-
cellent omnidirectional characteris-
tics .
Microphone Extension Rod Type
UA 0196 is supplied to ensure con-
formance of the complete instru-
ment to the omnidirectional require-
ments of the standards for precision
sound level meters. Only with an
omnidirectional sound level meter
can the user be sure, when making
community and industrial measure-
ments, that all noise sources are
measured accurately.
A plug-in microphone preampli-
fier permits use of microphone ex-
tension cables up to 1 00 metres
without degradation of most sig-
nals. Cables are available in stand-
ard lengths of 3, 10 and 30 me-
tres . Because the cables are in-
serted between the removable input
preamplifier and the sound level me-
ter, there is no influence of cable
capacitance on system perfor-
mance. A windscreen is provided to
reduce the effects of wind noise
when measuring outdoors. It also
finds use in protecting against dust
and oil spray when measuring in in-
dustrial environments.
The Condenser Microphone Type
41
65 is stable over wide ranges of
temperature and humidity . Its
quartz-coated diaphragm protects
against corrosive and humid envir-
onments in most cases. Back-ven-
ting permits its use with Dehumidi-
fier Type UA 0308 in high humidity
environments .
" IEC 651 Type 1 (Imp.) instruments correspond to the
earlier IEC recommendations 179 and 179 A in all
significant points
2
Features of Impulse Precision Sound Level Meters
Impulse sound level meters are designed in accordance with IEC 651 Type
(Imp.)* for measuring noise which has high peak values compared to RMS level
(called high crest factors). This category
of noise includes continuous sounds
such as auto motive exhausts and stamping machines, as
well as single im-
pulses from punch presses and pile drivers. Impulse sound le~el meters can mea-
sure high crest factor signals more accurately
than ordinary precision sound le-
vel meters.
Impulse sound level meters have an added "Impulse" meter response mode for
which the meter circuit has a rise time of 35 ms compared to 125 ms on "Fast"
and 1 son "Slow" response. The 35 ms rise time approximates· that of the ht;-
man ear, so that "Impulse" ·response more closely approximates subjective hu-
man loudness evaluation of impulse sou'nds having a rise time shorter than
1 25 ms. Some national standards specify the use of impulse sound level meters
to evaluate hearing loss risk due to impulse noise.
Bruel & KjCEr offers a variety of
microphones for special require-
ments. For measuring very high
noise levels, use a 1I 4 or 118 inch
microphone. For sound power meas-
urements in reverberant rooms, use
a 112
inch Condenser Microphone
Type 4134 to obtain a uniform ran-
dom incidence response up to
20kHz. And for measurements
down to 19 dB(A) use the 1 inch
Type 4145. Individual attenuator
scales are supplied so that less sen-
sitive microphones may be read di-
rectly in decibels. For complete spec-
ifications on individual micro-
phones, refer to the data sheet on
condenser microphones. See also
Fig.4 herein for mounting adaptors
that may be required.
The
impulse handling capability of
the 2209 provides accurate meas-
urement of signals with crest factor
up to 10 at full scale, increasing to
40 for readings 12 dB below full
scale. The 2209 provides A, B and
C-weighting for measuring sound le-
vel,
D-weighting for measuring air-
craft noise, and linear response for
measuring sound pressure and vi-
bration. Other features include
"Slow", "Fast", "Impulse" and "Im-
pulse Hold" response, "Peak Hold"
response, amplifier overload indica-
tor lamps, connections for external
filters, AC and DC recorder outputs,
and a built-in reference voltage for
convenient calibration check.
lnfrasonics
Infrasonic sounds occur in indus-
try when walls are excited by low
frequency vibrations which propa-
gate
through building structures
from remote machinery and air con-
ditioning equipment.
Infrasonic noise is not normally
detected on sound level meters be-
cause
signals below 10Hz are heav-
ily attenuated. When a 1 inch Con-
denser Microphone Type 4145 is
used and
the preamplifier is set to
it's low frequency range, the 2209
has a linear acoustical response to
about 2Hz . A Low Pass Filter with
22,5 Hz upper cut-off frequency
Type 5742 can be fitted to the com-
bination with 2209 and one of the
Filter Sets Type 1 61 3 or 1 61 6 to al-
low sound measurements in the In-
frasonic region between 2 and
22 ,5 Hz to be made. The Type
5742 is available from B & K Sys-
tems Engineering Group.
Ultrasonics
Ultrasonic measurements are re-
quired to measure noise emission
of ultrasonic welders and cleaners,
to tune ultrasonic welder~ to maxi-
mum efficiency and to calibrate all
types of ultrasonic transducers and
hydrophones in air . Some countries
have noise exposure criteria for ul-
trasonic sound. When used with
the 1I 4 inch Condenser Micro-
phone Type 41 36, the 2209 has a
linear response to above 70kHz.
True Peak Detection
When it is necessary to measure
the peak value of an acoustic wave,
the 2209 provides the capability .
This requirement occurs in stand-
ards for hearing loss risk which set
impulse noise limits based upon
peak sound pressure level. Other re-
quirements are found when measur-
ing vibrational shock and blast
noise .
In its "Peak Hold" mode the

2209 detects the peak value of the
input signal, using a rise time shor-
ter than 20 microseconds. Circuitry
then captures the peak level and dis-
plays it as a steady level on the me-
ter.
Vibration
Vibration reduction is often the
key to noise control. Because of this
close relationship between noise
and
vibration, the 2209 is designed
to quickly convert to a complete vi-
bration meter by replacing the mic-
rophone with the Integrator Type ZR
0020 and connecting an acceler-
ometer.
A circular calculating disc permits
rapid conversion from instrument
readings to units of displacement,
velocity or acceleration. When the
2209 is used to measure just one
vibration parameter, attenuator and
meter scales can be installed to
read directly in either acceleration,
velocity or displacement units.
• •
•
Fig. 1. Pistonphone Type 4220 and Sound
level Calibrator Type 4230
System Calibration
Two calibrators are available for
system acoustical calibration. The
Pistonphone Type 4220 provides a
250 Hz tone at a nominal sound
pressure level
of 124 dB (± 0,2 dB)
with an accuracy of 0,15 dB. The
Sound Level Calibrator Type 4230
provides a 1 kHz tone at a sound
pressure level
of 94 dB, with an ac-
curacy of 0,3 dB from 20 to 26 °C.
When using the 2209 as a vibration
meter, the Accelerometer Calibrator
Type 4291 provides a 10 ms-
2 peak
excitation signal at 79,6 Hz
(w=500). Calibrators also provide a
useful calibration signal for an associ-
ated tape recorder or graphic level
recorder.
Frequency Analysis
Measuring sound and vibration le-
vel is
usually only a part of long-
;
Fig. 2. The sound level meter equipped with integrator and accelerometer tor vibration measure-
ments, and 1/3 octave filter tor frequency analysis
term programs. Eventually, fre-
quency analysis is required. Octave
or third-octave frequency analysis is
required for enclosure and barrier
design and to test conformance to
Noise Criteria curves. And vibration
studies usually require narrow band
analysis. For this reason, the 2209
has provision for adding frequency
analysis filters.
Octave Filter Set Type 1 61 3 or
Third-Octave Filter Set Type 1 61 6
attaches directly to the sound level
meter and connects electrically by a
convenient connecting bar. The
1
61 3 contains 11 octave filters
with center frequencies from
31 ,5Hz to 31 ,5kHz. It features re-
cessed
adjustable attenuation con-
trol for each filter so the user can
normalize the read-out of all filters
to one convenient instrument read-
ing
when calibrating audiometers or
testing conformance to noise toler-
ance curves. The 161 6 contains 34
third;octave filters from 20Hz to
40kHz . The 1613 and 1616 meet
the most strict national and interna-
' tional standards for uniformity of fre-
quency response.
Portable Tunable Filter Type
1621 or Tracking Filter Type 1 623
can be used with the 2209, they
have selectable bandwidth as nar-
row as 3% of tune frequency on the
1621 and 6% on the 1 623.
Graphic Recording
The portable Level Recorders
Types
2306 and 2309 eliminate
the tedious task of plotting data by
hand, and they produce immediate
time history and frequency analysis
records which can be inserted di-
rectly into measurement reports.
When recording community noise
over long
time periods, the fiber
pens may be replaced by a stylus
scribing on waxcoated paper. The re-
sulting fine recording line permits
slower paper speeds while maintain-
ing an easily interpretable chart re-
cord. Frequency analyses are plot-
ted on frequency preprinted paper
in a
few seconds with octave, third-
octave or narrow band filter.
During long-term recording, bat-
tery condition can be monitored con-
tinuously on the meter.
Tape Recording
Sound and vibration signals should
be tape recorded when they must
undergo several kinds of frequency
analysis or be compared with new
data or new criteria. B & K offers the
Types 7005/6, which are portable
four channel instrumentation tape re-
corders for both field and laboratory
use, being small, light, and powered
from internal batteries. Easily ex-
changeable plug- in units permit any
combination of up to four IRIG Inter-
mediate Band Direct and Wide Band
FM channels to be obtained. Addi-
tionally, a Two Channel Compander
Unit may be fitted for automatic level
regulation
to obtain an effective
record- playback signal to noise ratio
of over 70 dB.
Fig.3. The Tape Recorder Type 7005
3

Audiometer Calibration
Because audiometers play a vital
role in measuring hearing loss and
in recognizing the onset of noise-in-
duced hearing loss, their accuracy
must be checked frequenctly. The
2209 becomes an audiometer cali-
brator when fitted with the Artificial
Ear Type 4152 or 4153 and Micro-
phone 4144 or 41 34 respectively.
It calibrates bone- conduction audi-
ometers when fitted with Artificial
Mastoid Type 4930. An octave or
third-octave filter is usually used to
isolate ambient noise and vibration
and to test for amplitude linear ity
and distortion . A practical carrying
case KE 0055, similar to that
shown in Fig.5, with provision for
accessories requiered for audiome-
ter calibration may be ordered separ-
ately .
Measuring Sets
The 2209 can be ordered with ac-
cessories according
to the need. A
carrying case should be included to
ensure that all items are in one set,
ready to be taken into the field on
short notice. To simplify ordering,
two sets containing the most com-
monly used accessories are offered.
The sturdy fibreglass carrying case
has a
molded foam interior for
safely storing the sound level me-
ter, fi Iter , caI ibrator, accessories
and noise
control records. It can be
carried aboard
aircraft to ensure
safe handling and prompt arrival at
the business and of your trip .
Sound and Vibration Sets
Types 3507 and 3511
Sound Level Meter
Octave Filter Set
Third Octave Filter set
Pistonphone
Accelerometer Set
Microphone 1 /2"
Nose Cone 1 /2"
Integrator
Adaptor for Tripod
Extension Cable
Carrying Case
B & K
Input Adaptor
Accessories
2209
1613
(3507 only)
1616
(3511 only)
4220
4366S
4166
UA 0386
ZR 0020
UA 0588
AO 0027
KE 0055
JP 0028
A wide selection of accessory
equipment is available to expand
4
AUDIOMETER CALIBRATION
Artificial Ear Artificial Ear
Artificial
Mastoid
•) Microphone Extension
Cable AD 0027 must
.,
be used 4153
1" Wind Screen
UA 0207
JJ~
4152 4930
DB 1021
Plug Adaptor
JP0028 ~Jl.!!!!.
41;>- - ~
1.L1lli
1613- AQ 0183
1616-AQ 0184
1 621-AQ 0034
~2:~t00_34_
t::UiJ
2306
Random 1" - 1/ 2"
Two Channel Level
Recorder 2309
Incidence Corrector 1" Microphone Adaptor
m m --~--~ --- o
Coonection r:
UA 00!>5
SOUND MEASUREMENT
4144
4145
DB 0962
1 ''- 1/2"
Cable
AD 0116
Flexible
Extension Rod
---r----- .... ~
4220
UNDERWATER
SOUND MEASUREMENT
UA 0196
Octave F ilter
Set16 13 or I
Th1rd Octave -1
FilterSet I
1616 I
I
I
AD 0116 I
I
~a~~~nectJon tf :
Tunable ~ _ _ i- ·;. ;ITrackong I
i~;~r ~ - - ~ :·: .~ · i ~;~ -_.J
Accessories included with 2209 underlined
Fig. 4. Survey of accessories available for sound and vibration measurements
the application possibilities of the
sound level meter . A survey show-
ing the connection possibilities of
the most useful items is given in
Fig. 4. For more information on the
individual instruments and transdu-
cers indicated, please ask for separ-
ate data sheets.
Technical Description
The Impulse Precision Sound Le-
vel Meter Type 2209 contains a
condenser microphone, plug-in
preamplifier, input attenuator ampli-
fier , selectable frequency-weighting
networks, output attenuator ampli-
fier, and detector circuit with mov-
ing coil meter. A built-in reference
oscillator provides a ready check of
amplifiers and meter circuit .
Fig.5. Sound and Vibration Set Type 3511
Microphone
The B &K Microphone Type 4165
is a prec1s1on condenser micro-
phone that has proven to be highly
stable and reliable. It has linear re-
sponse
in a free field when the
sound wave is at 0° incidence to -
the centerline axis (perpendicular to
the diaphragm). Response of the

complete instrument and the IEC
651 Type 1 tolerances for 0° inci-
dence are shown in Fig.6. The
2209 also has a linear response in
diffuse fields as required by ANSI
S.1.4-1971 Type 1 and shown in
Fig.7. The 2209 also meets the om-
nidirectional requirements of IEC
and ANSI. Directivity response of
the microphone and the complete
sound level meter are shown in
Figs.1 5
and 16.
A
calibration chart and frequency
response curve are supplied with
each microphone. Sensitivity is typi-
cally 50 mV /Pa with standard
200 V polarization voltage. The
4165 is extremely reliable and is
unaffected by wide ranges of tem-
perature and humidity. The diaph-
ragm is quartz-coated to protect
against humid and corrosive envi-
ronments.
Plug-in Preamplifier
The input preamplifier has a high
input impedance to permit measure-
ment at low amplitudes and low fre-
quencies with high impedance mic-
rophones and accelerometers. Be-
cause
the preamplifier is removable
and stays with the microphone,
long extension cables can be used
to locate the microphone at remote
measuring locations. Long cables
produce little or no effect on fre-
quency response except at very
high sound levels. See Fig.8.
A switch is located in the input
preamplifier socket for selecting the
instrument's low cut-off frequency.
See Fig.9. In its normal 10Hz cut-
off position, the switch is in its fully
anti-clockwise . position. Turn fully
clockwise for 2 Hz cut-off when
Fig.8. Maximum pennissible input voltage
with different lengths of extension
cable as a function of frequency
measuring infrasonic noise or low
frequency acceleration.
Amplifier
The input and output amplifiers
are each preceded by an attenuator,
the settings being controlled by two
concentric range selectors on the
front panel of the instrument. A ref-
erence calibration oscillator is ac-
companied by a system gain-adjust
potentiometer. The system's fre-
quency response is linear within
dB
+6
+4
+2
0
-2
-4
-6
-8
-10
-12
10
"
/
20 100 200
Hz
1 dB to 70kHz. Weighting network
A, B, C or D may be selected or ex-
ternal filters can be inserted bet-
ween the input and output amplifi-
ers.
The second section of the output
amplifier supplies 0,5 V RMS at full
scale deflection to the AC output
socket. Alternatively, 5 V RMS can
be
obtained from the third section
when the meter switch is set to
"Batt. (Rec)''. In this position, the
I
I
I
IEC 651
1--
v Type 1
1--
....
1--
-
~
'
.....
I\
\.
I
I
2 kHz 10 20
Frequency 760157 11
Fig.6. Free-field frequency response of complete instrument to sine waves with 0° incidence
dB
+6
+4
+2
0
-2
-4
-6
-8
-10
.......
""
-12
10
--
...,.....
20
......
""
-
--ra.
-!"-
100 200 Hz
2 kHz
-
~
'lj
I I I I
I I 1 l
I
ANSI 51.4- 1,971,_
./
,
\.~
\.I
I
I
10 20
Frequency
Type 1
1-
760156
Fig.7. Diffuse field (random incidence) frequency response of complete instrument
iii
~
~
c
0
~
a:
Q)
>
·~
Q;
a:
6
0
-2
-4
-6
-8
-10
-12
-14
IEC 179 Requirement
l--ol"--~"'----+---"l'---::--1 inch Mic~ophone ___ ,.._._ ______ -+------f
Direct I
t---~---+---t----=-1 /2 inch Microphone ---+--------+---- ---i
2 5 10 20 50
Frequency (Hz) 100
172011
Fig.9. Adjustable low frequency responses of the 2209 with 1" and 1 /2" microphones ·
5

Ext. Filter Conne ction
,-------- - - -- ,
I I
Microphone
m
"tl
+20
+10
Reference
Signal
c
Input
Ampl i fier
Phase
Converter
Overload
Indica tor
Ov erload
Inp ut
Attenuator
II
Power
Supply
+
3 to 4.6 Volt
Output
Amplifier
Fig.1 0. Block diagram of Type 2209
-
~
~
t'.......
A
Ove rload
Output
5! 0
c:
0
~-10
.,..,..,
,..----
I'"""
~
~
~
--
-
--:::::::
~
(8 +C)
/ /
Vo"
0
;;;.-'
7
/ /
/
/
/
a:
- ~ -20
<0
Qi
a: -30
-40
-50
-60
-70
10 2 5
/
..........
2 5 2 5 2
Frequency Hz 168217/ 1
Fig. 11 . Frequency response curves of the A. B. C and D weighting networks
+ 2 Meter deflection (dB rei to continued signal level) I I I
0
...,.
-- ...
IT ol~ran6e
1
"' ~'r'
1/.
~
/
~
IEC "Fast"
- 2
_.,,, .... Tolerance v / Tolerance
-4
L IEC
"lmpulse"f
/ IEC
"Slow "
I'
-6
/
~
_/
"Impulse · :.,_
_,.
"'
-, /
-8
-10
~
~
-"Slow " ,;
un
./
"Fast"
.I d
,U I~ I -12
/ 1/
~ / /
111
} r-1
L
~ ~
- I
f - 2kHz I
-14
-16
1 2 5 10 2 5
100 2 5 1000 Pulse length
t ( ms) 760165
Fig. 12 . Response of meter rectifier and meter to tone bursts of varying duration
meter monitors battery condition
during recording. The third section
of the amplifier also drives the me-
ter detectors.
Because
short duration, high am-
6
plitude signals can overload the am-
plifiers without causing the meter
to deflect above full scale, overload
indicators are provided for the input
and output amplifiers. The indica-
tors respond to either positive or ne-
Meter
Ampl ifier
and
"H o ld"
Circu it
Batt.
(R
ec.)
Meter
AC
Output
DC
O ut put
112239 / 1
gative peaks having durations as
short as 50 J.1S, and they continue to
flash for about one second after
overload.
Detector
The RMS detector can measure
signals with crest factors as high as
40, i.e. 32 dB peaks above RMS le-
vel.
The detector provides three
time constants, "Impulse", "Fast"
and "Slow" in accordance with
standards for precision and impulse
sound level meters. Fig.12 shows
the response of the 22 09 to tone
bursts of varying duration. Decay
time of the impulse circuit is 3 s.
This corresponds
to the 1,5 s decay
time constant of the Peak detector
circuit required in IEC 651 . "Im-
pulse Hold" permits the maximum
RMS level measured with the "Im-
pulse" time constant to be stored as
a steady
deflection for ease in mea-
suring impulse sounds . The meter
can be reset by momentarily de-
pressing
the "METER RESET'' but-
ton . The 2209 also has a "Peak
Hold" detector for measuring the
true peak value of noise and vibra-
tion signals . Rise time of the detec-
tor is approximately 10 J.lS .
A DC output of 0,8 V at full scale
deflection is available from the de-
tector circuit . The meter is a ribbon-
suspended moving coil type with a
removable meter scale. The scale is
graduated -1 0 to + 10 dB on its
"Sound Level Meter" side and 0 to

BO dB SPL
70
!6. II J I"
60.,.. 11111~..., ·~: .,...
'r '":"'"' ,· ~
20 50 100 200 500 1kHz
760160
Fig.13 . Equivalent sound pressure level
when complete sound level meter is
excited vertically at 1 m/s2. The
dotted line indicates sound level pro-
duced by vibration exciter
70 dB
SPL
c=:?l l_l
~~- ~I I
1 ms-
2
60~
1
~+-H- 4-~~ ~-1 --~-+ ~ -1-+++-H
~ ~~I
I~
4o JilL~~ .f:~~: : M
20 ~ 50~~~1~00~~~2~00~~ ~ 5 ~ 00 ~+ 1 ~ k~Hz
760159
Fig.14 . Equivalent sound pressure level
when complete sound level meter is
excited horizontally at 1 m/s2. The
dotted line indicates sound level pro-
duced by vibration exciter
10 and 0 to 30 on its "Vibration
Meter" side. Additional graduations
on each side permit battery condi-
tion check and calibration by the in-
ternal reference voltage.
Documentation
Bruel & Kjc:er sound level meter
specifications are supported by full
Fig.15. Directional characteristics of the microphone Type 4165 in a free-field
--;
>
Fig. 16. Directional characteristics of the complete instrument inclusive microphone and exten -
sion rod in a free-field
documentation so users can plan in-
terconnections with other instru-
ments and predict system noise in
vibration, acoustic and electromag-
Specifications 2209
netic environments. This documen-
tation eventually proves to be invalu-
able in most measurement pro-
grams.
(Specifications refer to 2209 with Extension Rod UA 0196 and Microphone 4165, unless otherwise stated)
Measuring Ranges:
Microphone Max .
Type
No . Level
(dB)
1"
4144-4145
140
1/ 2"
4165*- 4166
140
1/ 2"
4133-4134
150
• Included in 2209
Minimum dB Level (5 dB above noise floor)
Weighting Network
External Filter 1ype No.
1613 (Octave)
1616 (1/ 3 Octave)
0, 5- 0,5-
3i,5- 125- 20-
D A B c Lin
63Hz
250Hz
16 (31,5)
400Hz
16 (401 Lin
kHz
kH!
25
18
22 24
36
23 18 15 17 17
28
34
24
28
34 42
33 28
22 25
19 32
46 3q 40 46 56
45
40
34
37
31
44
Conformance to Standards:
The 2209 conforms to the requirements
of
IEC 651 Type 1, DIN 45 633 part 1
and ANSI S.
1.4-1971 Type 1 for preci-
sion sound level meters and IEC 651
Type 1 (Imp.) and DIN
45 633 part 2 for
impulse precision sound level meters
Reference Conditions for Instrument Cali-
bration:
Type of Sound Field: Free
Ref . Direction of Incidence: Perpendicu-
lar to microphone diaphragm
7

Ref . Sound Pressure Level: 84 dB re
20JJPa
Ref . Frequency: 1 kHz
Ref. Temperature: 20 °C
Ref. Measuring Range : 80 dB ( 90 dB
FSD)
Absolute Accuracy at Reference condi-
tions: ± 0,7 dB
Microphone:
Type:
B & K Free- field response 1/ 2" Conden-
ser Microphone Type 4165
Polarization Voltage:
200V
Frequency Response : At 0° incidence ;
Free- field
± 1 dB from 4Hz to 12 .5 kHz
± 2 dB
from 3 Hz to 20kHz
An individual response curve is supplied
with each microphone
Directional Characteristics: ·
See Figs. 15 ar I 16
Sensitivity :
Typically 50 mV / Pa . i ndividually cali-
brated
Temperature Coefficient :
Approx . -0 ,01 dB/ °C (- 0 , 055 dB/ ° F)
Permitted Temperature Range:
- 50 °C to + 60 °C (- 58 °F to + 140 ° F)
Effect of Ambient Pressure:
Approx . - 0 ,01 dB per kPa at 101 ,3 kPa
long Term Stability:
Better than 1 dB per 300 years at 27 °C
(81 °
F)
Typically 1 dB per 1 00 hours at 1 00 °C
(212 ° F)
Input :
Input Section:
Plugs in complete w i th Mi crophone cap-
sule
lmput Impedance :
> 1 GO //< 0,5 pF
Maximum Input Voltage:
10V (sine) RMS . See also Fig.8
Output :
Output Impedance : (load does not affect
meter deflection)
AC : 6000 (2000 in pas. "Batt. (Rec.)"
max. load 10 kO / / 200 pF . noise at least
50 dB below FSD voltage)
DC : 25k0
Output Voltage:
AC: 0,5 V RMS for FSD (5 V in "Batt.
(Rec.)" mode, max. 1OOV peak-to-peak)
DC : 0,8 V for FSD (dynamic range 25 dB)
Amplifier :
Attenuators:
20 to 140 dB FSD in 10 dB steps
Accuracy : 5Hz to 50 kHz ± 0,2 dB
2Hz to 80kHz ± 0.5 dB
Frequency Response :
±0,5
dB: 5Hz (20Hz) to 30kHz
± 1 dB: 2Hz(10Hz)to 70kHz
(F i gures in parentheses obtainable by
switch in input preamp)
Maximum Amplification:
114dB
Gain Adjust:
+ 3 to - 1 OdB
Inherent Noise :
Linear :
2
Hz to 70 kHz:
Max . 30JJV referred to imput *
10Hz to 70kHz :
Max . 30 JJV referred to imput **
Curve A:
Max . 2,8JJV referred to input **
* 300 pF across input , ** 60 pF across in-
put
Weighting Networks :
A, B, C and D weight ing plus linear am-
pl if ier response
External Filter Sockets :
Output Impedance : < 50 in series with
470JJF (max. load 5000)
Input Impedance: 1 46 kO
Indicating Meters:
Detector:
RMS (in pas. "Imp . Hold ", "Imp." ,
"Fast"
and " Slow " )
Crest Factor Capability:
10 at FSD i ncreasing to
40 at 12 dB below FSD
Meter Accuracy: (For crest factors up to
10)
± 0 ,5 dB from FSD to 12 dB below FSD
± 1 dB
from 12 dB to 20 dB below FSD
(The
se limi ts are increased by 0,5 dB for
crest factors between 10 and 20 and by
1 dB
for crest factors between 20 and
40)
PEAK: (in pas. " Peak Hold" )
Rise Time : < 20JJS
Meter Accuracy: ± 0,5 dB from FSD to
12 dB below FSD
Frequency Response: ± 1 dB from 2 Hz
(or 10 Hz) to 16 kHz
Damping :
" Impulse " , " Fast" and " Slow "
"Impulse Hold": decay time
< 0, 05 dB/ s
"Peak Hold": decay ti me < 0, 05 dB/ s,
rise time < 20JJS
Scale Graduations:
So u nd : 1 dB div i sions from - 10 to 0 dB.
0,5 dB divisions from 0 to + 10 dB
Vi
bration : 0 to 10 and 0 to 30 linear
Calibration:
Internal 2kHz oscillator , stability better
than ± 0.2 dB
Instrument Environment :
Operating Temperature Range:
-1 ooc to + 50 °C (+ 14 °F to + 122 ° F)
give less than ± 0,5 dB change in indica-
tion
Permitted Humidity Range:
The instrument is affected less than
0, 5dB between 0 and 90 % relative hu-
midity provided no condensation occurs
Effect of Vibration :
See
curves Fig. 13 and Fig. 14
Effect of Sound Field:
At least 60 dB below sensitivity of Micro -
phone Type 41 65
Effect of Electrostatic Field:
Negligible
with microphone gr id fitted
Effect of Electromagnetic Field:
80A / m (1 Orsted) (50 Hz) gives:
<
28 dB(D)
<
18dB(A)
< 28dB(B)
< 36dB(C)
< 36dB(Lin)
Batteries:
Type:
3 x 1,5 V IEC Type LR 20 Alkaline Cells
(e .g. Mallory Type MN 1300) B & K order
No. OB 0004
Life: (Continuous operation)
20 hours with recommended Alkal ine
batteries
14 hours with rechargeable NiCd-cells
(B & K order No. OB 0008 , 3rqd.)
(
Saft Volta block VR 4D)
(Varta
RS 4)
Recharging
from Power Supply Type
2808 , Battery Box ZG 0146 and Charg-
ing Adaptor AO 0157 + 3 Dummy cells
ZR 0017
8 hours with standard dry cells
Dimensions :
length : 325 mm (12 ,8 in) (545 mm
(21 ,5 in) w i th Extension Rod UA 0196)
Width: 120 mm (4 ,8 in)
Height: 90 mm (3 ,5 in)
Weight:
3 kg (6 ,6 lb)
Accessories included:
1/ 2" Condenser Microphone 4165
Input Stage ZC 0007
Flexible Extension Rod UA 0196
Input Adaptor JJ 2614
Windscreen UA 0237
4 Screened Plugs JP 0006
Attenuator Scales SA 0012 to SA 0021
Screwdriver QA 0001
Accessories Available :
See survey Fig.4

2. CONTROLS
Protection Grid ---------
Output Attenuator (Transparent)
Input Overload
External Filter In
External
Filter Out
Weighting Network Switch
Fig.2.1.
--------- Microphone
13-- --------- Extension Rod UA 0196
Input Attenuator (Black)
Output Overload
-.,;....-- Meter Reset
Meter Scale
Power
770114
Front view of 2 209
9

MICROPHONE:
PROTECTION GRID:
EXTENSION ROD
UA 0196:
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.
If a Dehumidifier Type UA 0308 is used, it is placed between the mi-
crophone 3nd the extension rod.
When screwing the microphone, extension rod, and sound level meter together, only
light finger torque should be used.
METER SWITCH: This
7-position rotary switch is both the power switch and meter func-
tion selector, with positions as follows:
"Off": Power off position. In all the other positions the power is on ,
and
the POWER lamp flashes.
"Batt.(Rec.)": Battery check position. If the meter needle deflection is
below the red area, the batteries must be replaced. If the meter needle
deflection is on the red block, the instrument may be used for a short
time before battery replacement is necessary. A higher meter needle
deflection indicates sufficient battery power.
"Slow": Provides a "Slow" meter response. (See Fig. 12 in Chapter 1 .)
"Fast": Provides a "Fast" meter response. (See Fig. 12 in Chapter 1.)
"Imp." : Provides the "Impulse" meter response for measurement of
subjective level of short-duration sounds. (See Fig.12 in Chapter 1.)
"Imp. Hold": Holds the maximum RMS value of the applied signal until
the METER RESET button is depressed. Rise time is the same as that
for "Imp." response; decay rate is < 0,05 dB/s.
"Peak Hold" : Holds the maximum peak value of the applied signal until
the METER RESET button is depressed. Rise time is< 20 J1S.
POWER: This lamp flashes when the instrument is switched on.
WEIGHTING NETWORK SWITCH: This 6-position switch determines the frequency-response characteris-
tics of the instrument's electronics, and the selection of an external fil-
ter, as follows:
10
"A", "B", "C", "D": Each of these 4 positions selects one of the stan-
dardized frequency-weighting networks for the subjective indication of
loudness. (See Fig.11 in Chapter 1 .)

METER SCALE:
"Lin.": Gives linear frequency response from 2Hz (or 10Hz; see sec-
tion 3.2.2) to 70kHz.
"Ext. Filter": Selects an external filter connected to the EXTERNAL FIL-
TER sockets. No meter needle deflection will be obtained in this posi-
tion if a filter is not connected.
This is a double-sided scale which may be removed by sliding it out to
the right. One side is calibrated for precision sound level measure-
ments and the other side for vibration (or voltage) measurements.
"Precision Sound Level Meter" scale: The upper scale (black) is cali-
brated from "-1 0" dB to "+ 1 0" dB for the reading of sound level.
"0" dB on the scale corresponds to the attenuator setting indicated in-
side the red lines. Thus, for example, if the meter shows "-2" dB and
the attenuator setting is "70" dB, then the sound level is 68 dB. The
lower scale (red) is used for calibration of the instrument using the sen-
sitivity of the microphone which is found on its individual calibration
chart. When checking the batteries (with the METER SWITCH in "Batt.
(Rec.)" position), the meter needle deflection must be within the black
lines labelled "Battery" on the lowest meter scale, and above the red
block
for long-term use.
"Vibration Meter" scale: The upper scale (black) is calibrated from "0"
to "1 0" and "0" to "31 ,6" in linear units. The vibration level (or volt-
age) is then the meter reading referenced to the full-scale deflection
shown inside the red lines, when the appropriate ATTENUATOR
SCALE is
fitted. The lower scale (red) is used for calibration of the in-
strument using the sensitivity of the accelerometer (see section 3.5.3)
which is found on its individual calibration chart. The "Battery" check
scale is
the same as the one on the other side of the METER SCALE.
METER
MECHANICAL ZERO
ADJUSTMENT: The screw head just below the METER SCALE is adjusted with the in-
strument switched off to give a meter needle deflection on the "-«~"
mark ("Precision Sound Level Meter" scale) or the "0" mark ("Vibra-
tion Meter" scale).
METER RESET:
This push button resets the meter when using the "Imp. Hold" or
"Peak Hold" position.
INPUT SOCKET SWITCH:
This screwdriver-operated switch is located in the centre of the input-
stage socket; see section 3.2.2. The lower frequency limit of the instru-
ment is 2Hz with this switch fully clockwise and 10Hz with it fully an-
ticlockwise.
Since the 2209 can measure sound levels (and vibration levels or voltages) over a wide
dynamic range (from 24 dB to 140 dB for sound levels, for example) but the METER
SCALE can
only accurately display 20 dB of this range at a time, an attenuator system is
necessary
to set the range of the instrument so that the sound level (or vibration level or
voltage) will be within the 20 dB indicated on the METER SCALE. In order to minimize
the chances of an overload, and to give the best possible signal-to-noise ratio, a dual
attenuator system consisting of INPUT and OUTPUT ATTENUATORS is used. The correct
use of these switches is described in Chapter 3, Operation.
11

INPUT ATTENUATOR (black):
OUTPUT ATTENUATOR
(transparent):
ATTENUATOR SCALE:
GAIN
ADJ .:
INPUT and OUTPUT
OVERLOAD:
EXTERNAL FILTER IN :
EXTERNAL FILTER OUT:
This 9-position switch controls the gain of the input amplifier in 10 dB
steps, and also selects
the internal reference voltage. The range of this
switch is physically limited to a position from "60" dB to "Ref ." being
adjacent to the black spot. (If ATTENUATOR SCALES other than No.
1A are used,
then different values will be noted .) Maximum input gain
is obtained in the fully clockwise position; and the internal reference
voltage is selected in the fully anticlockwise position (provided the
transparent OUTPUT ATTENUATOR is also set to its fully clockwise po-
sition) .
This 6-position switch controls the gain of the output amplifier in
10 dB steps. The range of rotation of this switch is physically limited
so that · the red lines on the knob may only be moved anticlockwise
from the black dot. Maximum output gain is obtained in the fully anti-
clockwise position, while the minimum output gain (red lines by the
black dot) is recommended for use whenever possible.
The total gain setting depends on both INPUT and OUTPUT ATTEN-
UATOR positions; the measuring range corresponding to the gain
setting is always directly indicated between the red lines on the
knob.
Ten reversible ATTENUATOR SCALES are provided with the 2209 to
permit direct reading of virtually any sound, vibration or voltage unit
within the range of the instrument. The SCALES are changed by un-
· screwing the large screw in the centre of the attenuator knobs with a
coin
or a large screwdriver and removing the transparent knob. Ensure
that the small cut - out in the SCALE by the "Ref." mark is correctly lo-
cated over the pin in the black knob, and then refit the transparent
knob (ensuring its correct location) and the screw.
This screwdriver-operated potentiometer is used for adjusting the gain
of the input amplifier over a range of 13 dB to permit calibration with
various transducer sensitivities. It is adjustable from -10 dB to + 3 dB.
Separate
flashing lamps indicate any overload of the input and/or out-
put amplifiers . The INPUT and/or OUTPUT ATTENUATORS should be
adjusted as necessary
to remove the indicated overload which will oth-
erwise give erroneous readings. If an overload cannot be remoyed, it
should be noted with the measurements.
Socket for connection to the input of an external filter (such as Octave
Filter Set Type 1
613 or 1/3 Octave Filter Set Type 1 61 6). The mini-
mum load impedance of the socket is 500 0 . Accepts plug JP 0006 or
cable AO 0007, etc ..
Socket
for connection to the output of an external filter to the 2209. In-
put impedance of the socket is 146 kO. The maximum input voltage is
0,2 V RMS, 2 V Peak. Accepts plug JP 0006 or cable AO 0007, etc ..
The EXTERNAL FILTER
IN and OUT sockets may be connected to a 161 3 or a 161 6 di-
rectly by means of the Connection Bar JP 0400 supplied with each filter.
12

DC OUTPUT:
AC OUTPUT:
TRIPOD-MOUNTING THREADS:
This socket provides a DC voltage from the meter rectifier, giving 0,8 V
(open
circuit) for full-scale meter needle deflection, with an output im-
pedance of 25 kO. The meter reading is not affected by loading this
socket. Accepts plug JP 0006 or cable AO 0007, etc..
This socket provides an AC voltage from the output amplifier. With the
METER SWITCH set to "Batt. (Rec.)", the output is 5 V RMS (for full-
scale deflection) into a load of not less than 10 kO. With the METER
SWITCH set to "Slow", "Fast", "Imp.", "Imp. Hold", or "Peak Hold",
the output is 0,5 V RMS (for full-scale deflection) with an output imped-
ance of 600 n, and any load may be applied without affecting the me-
ter reading. These output voltages are open-circuit values, and are suit-
able for use with a Tape Recorder, etc .. Accepts plug JP 0006 or
cable AO 0007, etc ..
There are two tripod-mounting threads on the rear of the 2209, the up-
per for mounting the 2209 alone, and the lower for mounting the
2209 when fitted with a filter set (Type 161 3 or 161 6). For vertical
mounting, a thread is also provided on the bottom of the 2209.
13

3. OPERATION
3.1. INTRODUCTION
This Instruction Manual describes the specific procedures necessary to correctly use the
Impulse Precision Sound Level Meter Type 2209. However, there are many aspects of
sound measurement of a more general nature that are important to consider in order to
get correct reproducible measurements. Many of these are discussed in the accompany-
ing booklet, "Measuring Sound", which should be considered as part of this Instruction
Manual .
3.2. PRELIMINARIES
3.2.1. Battery Considerations
14
The 2209 is powered by three st~ndard torch batteries (D cells or Type R 20 in IEC Publi-
cation 86-2). Access to the batteries is gained by sliding the rear cover off the instru-
ment. The batteries should be inserted with polarities as shown in the battery compart-
ment. See Fig.3.1.
Fig. 3. 1. Battery compartment of 2209
Good-quality dry cells give an operating time of 8 hours, while alkaline cells such as Mal-
lory Duracell MN 1 300 give 20 hours of continuous operation. Rechargeable nickel-cad-
mium cells may also be used, giving an operating time of 14 hours. These cells may be
recharged
using the Power Supply Type 2808 with Battery Box ZG 0073 and Charging
Adaptor AQ 0043 -see the 2808 Instruction Manual.