Product Data: Probe Microphone — Type 4182 (bp0659)

Product Data: Probe Microphone — Type 4182 (bp0659)
Product Data
Probe Microphone — Type 4182
USES:
FEATURES:
❍ Near-field measurement of loudspeakers
❍ Smooth frequency response characteristic between
1 Hz and 20 kHz
❍ Investigation of sound distribution inside:
❍ Small size and lightweight (only 45 g (1.47 oz))
Telephone equipment
Hi-Fi headphones
Musical instruments
❍ Selection of interchangeable stiff and flexible probe
tubes
❍ Measurement of noise radiation from intricate
machinery
❍ Probe-tip can withstand temperatures up to 700°C
(1292°F)
❍ Measurement of attenuation in hearing protectors
❍ High acoustic impedance
❍ Acoustic impedance measurements
❍ Pressure equalization with the measurement site
Probe Microphone Type 4182 allows
sound pressure measurements to be
made in small or awkward places or in
harsh environments where a conventional microphone would be unsuitable. The probe microphone has a
smooth frequency response from 1 Hz
to 20 kHz, with a very smooth highfrequency roll-off.
Physically, it is very small and lightweight and has a durable construction.
Measurements can be performed extremely close to the sound source due
to its small size. Measurement points
can be closely spaced when it is necessary to have high spatial resolution.
The high impedance of the narrow
probe tip enables measurements in
very small volumes – as small as 1 cm3
with only minor effects due to acoustic
loading. Interchangeable stiff and flexible probe tubes, of various lengths,
make the probe microphone very
adaptable for measurements in awkward places (for safety reasons Probe
Microphone Type 4182 is not suitable
for measurements on the human body).
The static pressure inside the probe
microphone can be equalised to that of
the measurement site.
Description
Frequency Response
Probe Microphone Type 4182 is distinguished by a smooth frequency response between 1 Hz and 20 kHz,
with a very smooth high-frequency
roll-off. This smooth response means
you can use equalization or a post-
Brüel & Kjær
B
K
932174e
processing correction. Fig. 1 shows
four individual frequency response
curves for the probe microphone,
each measured with a different
length of stiff probe tube. The highfrequency roll-off increases for increasing probe tube length. The differences in low frequency responses
are dependent on static pressure
equalization. The probe microphone
is individually calibrated with the
50 mm
tube
attached.
Using the probe microphone allows
you to make measurements in very
harsh conditions. The tips of the
100 mm and 200 mm stiff probe tubes
can withstand temperatures of up to
700°C.
Response with Flexible Probe Tubes
For very difficult measurement situations, you can fit a flexible probe
tube on the probe microphone. The
frequency response will, however, be
slightly different. 150 cm of the flexible probe tubing is included. Fig. 2
shows the frequency response with
flexible probe tubes attached. The
more severe high-frequency roll-off is
due to the narrower internal diameter of the flexible tubing. You should
calibrate the probe microphone when
using the flexible tubing.
Construction
An important design feature of Probe
Microphone Type 4182 is the internal, impedance matching tube surrounding the preamplifier. This
impedance matching tube is used to
match the impedance at the exit of
the tiny cavity in front of the microphone diaphragm. This significantly
reduces the effects of reflections within the probe tube and provides the
microphone with its characteristic
smooth response.
Fig. 4 is a simplified drawing showing the continuous passage formed by
the probe tube, the cavity in front of
the microphone diaphragm and the
impedance matching tube.
You can make measurements in
high-pressure environments by connecting a tube from the external vent
into the measurement environment
to equalize the static pressure.
The narrow probe tubes provide
the probe microphone with a very
high acoustic impedance (approx.
8 × 108 Ns/m5). Above 50 Hz, there is
negligible acoustic loading to volumes
of 1 cm3 or greater.
Noise and Crosstalk
Careful design means that the probe
microphone has a low sensitivity to
unwanted acoustic signals that could
be transmitted through the probe
body and tube walls. The curves in
Fig. 3 represent the typical sensitivity of the microphone with the probe
tip open and closed. Up to 500 Hz, the
sensitivity of the microphone with a
closed tip decreases by 6 dB/octave
due to sound arriving at the pressure
equalization vent. The A-weighted inherent noise of the probe microphone
is less than 42 dB SPL.
Microphone and Preamplifier
The built-in microphone is similar to
a standard Brüel & Kjær 1/4″ con-
+5
+1
0
+1
25 mm
50 mm
–5
100 mm
200 mm
– 10
20
50
100
200
500
1000
2000
5000
10000
Hz
20000
940435e
Fig.1 Typical frequency responses for various stiff probe tube lengths
Frequency Response Check and
Calibration
Check the frequency response using
Calibration Coupler UA 0922 together
with Transmitter Adaptor UA 0920.
The adaptor uses Condenser Microphone Type 4188 (available separately) as a sound source. You can use
Condenser Microphone Type 4136
(available separately) as a reference
microphone when you are making a
frequency response calibration.
denser microphone. The probe microphone can be connected to the
Preamplifier
Input
of
any
Brüel & Kjær frequency analyzer or
measuring amplifier. The output
characteristics of the integral preamplifier are similar to those of Microphone Preamplifier Type 2670. Probe
Microphone Type 4182 requires a
200 V polarization voltage.
Accessories
Examples of Use
Sensitivity Calibration
Use Adaptor UA 0929 for sensitivity
calibration of the probe microphone
with Pistonphone Type 4228 or
Sound Level Calibrator Type 4231.
Type 4182 is supplied with an adaptor ZG 0350 for connection to traditional
Brüel & Kjær
microphone
sockets.
Probe Microphone Type 4182 is ideal
for measuring very close to a sound
source. For example, measurements
on loudspeakers, automobile engines,
or making in-situ measurements on
headphones, hearing protectors, telephones and musical instruments. For
safety reasons, measurements on the
10
Probe tip
open
0
dB
4
–10
2
–20
0
dB
50 mm Flexible Probe-Tube
–30
–2
–4
–40
100 mm Flexible Probe-Tube
–6
Probe tip
closed
–50
–8
– 10
–60
– 12
–70
– 14
–80
500
1k
2k
Hz
5k
10k
20k
50k
882003/1e
5
10
20
50
100 200
Hz
500
1k
2k
5k
10k 20k
891771/1e
Fig.2 Typical frequency responses for various flexible probe tube Fig.3 Comparison of typical sensitivities with probe tip opened (uplengths
per curve) and closed in 1 m3 rigid cavity (lower curve)
2
Fig.4 Schematic representation of the internal construction of Probe Microphone Type 4182 showing the microphone cavity, equalization
vent and impedance matching tube
human body must not be made with
Probe Microphone Type 4182.
The probe microphone can also be
used as a reference microphone with
the Brüel & Kjær Spatial Transformation of Sound Fields (STSF) System. This uses near-field sound
measurements to predict far-field behaviour. With its small size, it is easy
to get close to the near-field using the
probe microphone.
Measurements on Exhaust Systems
Usually you have to make these
measurements at the source. For
measurements in smaller systems
such as car exhausts, the tip of the
probe tube can be inserted directly
into the exhaust channel. You can expose the tip of the probe tube to temperatures up to 700°C, however you
must make sure that temperature of
the microphone body is not greater
that 50°C.
When you are using the probe microphone for exhaust system measurements, water may condense inside
the probe tube system. To avoid damage to the built-in microphone use
the 200 mm probe tube and make
sure the pressure at the measurement point is not greater than
10000 Pa (0.1 bar).
In large systems, a metal
waveguide tube is inserted through
the wall of the exhaust channel (see
Fig. 5). The waveguide uses a long
flexible hose to provide proper acoustic termination. The end of the hose
is sealed to prevent exhaust gas flow
in the waveguide. If the attenuation
in the waveguide is taken into account, the sound pressure in the
waveguide is equal to the sound pressure in the exhaust channel. The
probe microphone can then be used
to measure in the waveguide. For
good results, the internal area of the
waveguide should be greater than
13.25 mm2 (dia. 4.1 mm).
The waveguide’s internal area
should also be 25 times smaller that
the exhaust channel’s internal area.
An equalisation tube connects the microphone pressure equalization vent
to the tube. You can also measure the
attenuation across filters in the exhaust channel.
Acoustic Impedance Measurements
Acoustic impedance measurements
help determine the loading and efficiency of transmission paths and
transducers. Because of its small size
and high impedance, the probe microphone is ideal for in-situ measurements of acoustic impedance in ducts
or on telephones and earphones, as
well as helmets and masks equipped
with communication devices.
Fig.5 Diagram showing application of the probe microphone for noise measurements on
exhaust systems or chimneys
3
Specifications 4182
SENSITIVITY (250 Hz):
–50 dB ±3 dB re 1 V/Pa (nom. 3.16 mV/Pa) (individually calibrated)
PRESSURE RESPONSE:
2 Hz
: +1.5 dB (no SPL at vent)
5 Hz
: +1.0 dB (no SPL at vent)
10 Hz : +0.8 dB
20 Hz : +0.5 dB ± 0.5 dB
100 Hz : +0.2 dB ± 0.5 dB
250 Hz :
0 dB
1 kHz : –0.3 dB ±0.5 dB
2 kHz : –1.0 dB ±0.7 dB
5 kHz : –2.5 dB ±1.0 dB
10 kHz : –5.0 dB ±1.5 dB
20 kHz : –11.0 dB ±3.0 dB
(50 mm probe, 23°C (73.4°F), ref. 250 Hz)
The high-frequency roll-off is due to probe tube
loss
ACOUSTICAL INPUT IMPEDANCE:
8 × 108 Ns/m5 (approx.)
ELECTRICAL OUTPUT IMPEDANCE:
25 Ω (max.)
DISTORTION: < 3% below 164 dB SPL (100 Hz)
EQUIVALENT INHERENT NOISE:
<42 dB SPL (A)
<50 dB SPL (lin. 20 Hz to 20 kHz)
CONNECTOR TYPE:
LEMO type FGG.1B.307
MAXIMUM STATIC PRESSURE BETWEEN
PROBE SYSTEM AND ENVIRONMENT:
10000 Pa (0.1 bar) recommended
MAXIMUM STATIC PRESSURE BETWEEN TIP
AND VENT:
300 Pa, (1% sensitivity change)
10000 Pa (0.1 bar), (damage risk limit)
AMBIENT PRESSURE COEFFICIENT (250Hz):
–0.0007 dB/mbar
Dimensions and Weight
Probe Tube Lengths: 1 × 25 mm (0.99″)
1 × 50 mm (1.97″)
2 × 100 mm (3.94″)
1 × 200 mm (3.94″)
Note: All values are typical at 25°C (77°F), unless measurement uncertainty or tolerance field
is specified. All uncertainty values are specified
at 2σ (i.e. expanded uncertainty using a coverage factor of 2)
COMPLIANCE WITH STANDARDS:
CE-mark indicates compliance with: EMC Directive.
Safety
EN 61010–1 and IEC 1010–1: Safety requirements for electrical equipment for
measurement, control and laboratory use.
EMC Emission
EN 50081–1: Generic emission standard. Part 1: Residential, commercial and
light industry.
EN 50081–2: Generic emission standard. Part 2: Industrial environment.
CISPR 22: Radio disturbance characteristics of information technology
equipment. Class B Limits.
FCC Rules, Part 15: Complies with the limits for a Class B digital device.
EMC Immunity
EN 50082–1: Generic immunity standard. Part 1: Residential, commercial and
light industry.
EN 50082–2: Generic immunity standard. Part 2: Industrial environment.
Temperature
IEC 68–2–1 & IEC 68–2–2: Environmental Testing. Cold and Dry Heat.
Operating Temperature: –10 to +50°C (14 to 122°F)
Storage Temperature: –25 to +70°C (–13 to 158°F)
IEC 68–2–14: Change of Temperature: –10 to +50°C (2 cycles, 1°C/min.)
Humidity
IEC 68–2–3: Damp Heat: 90% RH (non-condensing at 40°C (104°F)). The
absolute value of humidity (46 g/m3) must not exceed the value for 90% relative
humidity at 40°C (104°F)
Environmental
TEMPERATURE RANGE:
Probe Tip:
Up to 700°C (1292°F) with 100 mm probe tube.
Temperature calibration needed, see Instruction
Manual.
TEMPERATURE COEFFICIENT (250 Hz):
–0.005 dB/°C
VIBRATION SENSITIVITY (f <300 Hz):
68 dB SPL at 1 ms–2
Worst Case: axial direction
MAGNETIC FIELD SENSITIVITY:
45 dB SPL at 50 Hz, 80 A/m
PRESSURE EQUALIZATION MODES:
Vented to the ambient pressure at the housing,
or to the static pressure at the measurement site
via an external tube.
Time Constant = 0.05 s to 0.53 s
Probe Tube Diameter: 1.24 mm (0.05″)
Probe Housing Diameter: 13.5 mm (0.53″)
Probe Housing Length: 118.5 mm (4.67″)
Probe Weight: (excl. cable): 45 g (1.47 oz)
Cable Length: 2 m (6.6 ft)
Cable Weight: 20 g/m (0.65 oz/yd)
Ordering Information
Type 4182
Probe Microphone
Includes the following accessories:
UA 0926:
Set of probe tubes with
impedance matching tubes
AF 0555:
Flexible Probe Tube (1.5 m)
UA 1066:
Flexible Probe Tube Stud
DB 2930:
Venting-tube Stud
2 × DH 0549:
Cleaning Needle
QA 0159:
Wrench
UA 0922:
Calibration Coupler
2 × UA 0939:
Calibration Stop
UA 0929:
Pistonphone Adaptor
UA 0920:
Transmitter Adaptor
Type 4188:
UA 0801:
UA 0588:
1/2″ Condenser Microphone
Tripod
Tripod Adaptor
Optional Accessories
B & K to B & K
AO 0027:
AO 0028:
AO 0029:
Extension Cables:
Extension cable 3 m
Extension cable 10 m
Extension cable 30 m
General:
Type 4231:
Type 4228:
Type 4136:
LEMO to LEMO Extension Cables:
AO 0414:
Extension cable 3 m
AO 0415:
Extension cable 10 m
AO 0416:
Extension cable 30 m
JP 0169:
DP 0651:
DP 0652:
ZG 0350:
Short-circuit Plug
Plug (spare)
Plug (spare)
LEMO to 7-pin Brüel & Kjær
adaptor
Sound Level Calibrator
Pistonphone
1/4″ Condenser Microphone
Brüel&Kjær reserves the right to change specifications and accessories without notice
Brüel & Kjær
B
K
WORLD HEADQUARTERS:
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United Kingdom and Ireland (0181) 954-236 6 · USA 1 - 800 - 332 - 2040
Local representatives and service organisations worldwide
BP 0659 – 15
95/04
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