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Product Data: Sound Intensity Probe Sets Product Data Sound Intensity Probe Sets — Types 3583, 3584 Sound Intensity Microphone Pairs — Types 4178, 4197 Dual Preamplifier — Type 2682 USES: FEATURES: ❍ Measurement of sound intensity using two- ❍ Microphone pairs matched for phase and amplitude microphone technique, in accordance with IEC 1043 response Class 1 ❍ Individual calibration data ❍ Sound power measurements in accordance with ❍ 1 /3-octave centre frequency ranges: ISO 9614–1, ISO 9614–2, ECMA 160 and 3583: 20 Hz to 10 kHz ANSI S 12–12 3584: 20 Hz to 6.3 kHz ❍ Minimal shadow and diffraction effects ❍ Well-defined acoustical microphone separation The transducer is the first stage in many measurement chains. Its relia- bility determines the ultimate accura- cy of the system. This is especially so for sound intensity measurements with a two-microphone technique where stringent requirements are placed on the phase and sensitivity matching be- tween the probe microphones. Types 3583 and 3584 are two-micro- phone probe sets for measuring sound intensity with Brüel&Kjær’s range of sound intensity analyzers. These probe sets feature precision, phase and sensi- tivity matching between the probe micro- phones. All the probe sets are supplied with a 1/2″ Sound Intensity Microphone Probe Set Type 3583 in carrying case Pair Type 4197, enabling measurements between 1/3-octave centre frequencies of 20Hz and 6.3kHz. With 1/2″ micro- phones the probe sets comply with IEC1043 Class 1. Type 3583 also in- cludes a 1/4″ Microphone Pair Type 4178, extending the upper 1/3-octave centre fre- quency to 10kHz. The Remote Control Unit ZB0017 is part of Type 3584. Re- mote Control Unit ZH0354 is available for Type 3583. 1/2″ Sound Intensity Microphone Pair Type 4197 features phase-correc- tor units which make precision low- frequency phase matching a practical An possibility, leading to increased meas- assembled probe urement range and accuracy. A phase- Probe Set Type 3584 in carrying case matching calibration chart is supplied with each microphone pair. B Brüel & Kjær 7/6-'89 K Introduction Measurement of sound intensity (sound power per unit area) is in- creasingly being used as a routine technique in a wide range of noise investigations. The method permits the determination of sound power from direct measurement of sound in- tensity, even in situations where pressure-based measurements would be impossible. Since the method does not require special acoustic environ- ments such as reverberation and ane- choic chambers, significant savings can also be made. To measure sound intensity accu- rately using a two-microphone tech- nique, you need a reliable sound intensity probe set containing a matched microphone pair to obtain information on both the instantane- ous pressure and pressure gradient in the sound field. The microphones Fig.1 A sound intensity probe consists of: Dual Preamplifier Type 2682, Sound Intensity are separated by a fixed distance in Microphone Pairs Types 4197 and 4178 and spacers the sound field, and the microphone signals are fed to a sound intensity Probe Description an analyzer remote control unit at- processor which calculates the sound tached to the probe set. All the probe intensity. The sound intensity is cal- The sound intensity probe sets are sets are supplied in attaché cases culated from the time average of the constructed in similar ways. They containing the microphone pairs, sound pressure multiplied by the par- consist of a robust frame (see Fig.1) windscreens (spherical and ellipsoi- ticle velocity (calculated from the which holds the microphone pream- dal) and accessories. In addition measured pressure gradient). Such a plifier(s) and matched microphones Type 3584 is supplied with Remote system measures the component of in the face-to-face configuration. The Control Handle ZB 0017. the sound intensity along the probe distance between the microphones is axis and also indicates the direction defined by solid plastic spacers which Sound Intensity Probe Sets of energy flow. are held in place by threaded studs Both probe sets are supplied with Two sound intensity probe sets are on the microphone grids. Sound is 1/2″ Sound Intensity Microphone Pair available from Brüel & Kjær: Types constrained to act on each micro- Type 4197 for measurements in the 3583 and 3584. The characteristics of phone through a narrow slit between the probe sets and the sound inten- the spacer and the microphone grid. low and medium frequency ranges. 1 ″ sity microphone pairs 4178, 4197 are This arrangement gives well-defined Type 3583 also includes /4 Sound described in this product data sheet. acoustic separation of the micro- Intensity Microphone Pair Type 4178 For further details of the sound in- phones and minimizes shadow and for measurements in the medium and tensity analyzers and information on reflection effects. high frequency ranges (Fig.1). These which probe set is suitable for which The probe sets are strong but light- 1/4″ microphones are also available analyzer, see the separate product weight and can be held using either separately for use with the other data sheets for the analyzers. a handle and extension rod, or with probe sets. Both Type 4197 and 4178 2 B Sound Intensity Microphone Pair FrequencyFree-field Response response (re 250Hz) 0° Sound : Incidence 7/6-'89 K Deg. Measurement of phase difference Type 4197 The free-field response for the microphone when mounted in the 1.8 The microphones are mounted in a face-to-face face-to-face, sound intensity probe configuration with sound Bruel & Kjær Calibration Chart configuration with the pressure equalization ° ° perpendicular——— to itsPart diaphragm 1 ——— (0 or 180 ———). Part 2 ——— 1.6 vents also exposed to the sound field. Serial No: 2113339 Part 1 Part 2 1/3 OctaveThe response Actuator is valid with Free the Field 12 mm Actuatorspacer in position. Free Field Open-circuit Sensitivity, S : dB re 1V/Pa Centre Response Response Response Response 0 -38.5 -38.5 ° ° 1.4 Frequency0 0 Sound 0 Sound180 Equivalent to: 11.9 11.9 mV/Pa Incidence Incidence Uncertainty, 95 % confidence level 0.2 dB + 3 [Hz] [dB] [dB] [dB] [dB] Capacitance: 19.6 19.8 pF 1.2 Part 1 dB250 -0.00 -0.00 -0.00 0.00 + 1 Vent Sensitivity, 20 Hz: - - - - - (re diaphragm sens.): -77.7 -73.2 dB 1 10000 -0.09 0.01 -0.09 0.01 Phase difference – 1 Valid At: 1250 -0.13 0.01 -0.13 0.01 0.8 Positive: Temperature: 23 ° 1600 -0.20 0.01 -0.20 0.01 C Negative: Ambient Static Pressure: 101.3 kPa – 20003 -0.30 0.01 -0.31 -0.00 Limit: 2500 -0.46 -0.00 -0.47 -0.02 Relative Humidity: 50 % 0.6 + 3 Frequency: 251.2 Hz 3150Part 2 -0.69 -0.02 -0.72 -0.05 Polarization Voltage, external: 200 V dB4000 -1.04 -0.01 -1.09 -0.06 0.4 + 1 Sensitivity Traceable To: 5000 -1.54 0.01 -1.59 -0.05 0 DPLA: Danish Primary Laboratory of Acoustics 6300 -2.39 -0.11 -2.45 -0.17 NIST: National Institute of Standards and Technology, USA 0.2 – 80001 -3.33 -0.01 -3.42 -0.09 10k -4.62 0.18 -4.71 0.09 Environmental Calibration Conditions: 0 – 3 101.4 kPa 25 °C 30 % RH 31.563 125 250 500 1.0 k 2 k 4 k 8 k 200 500 1 k 2 k 5 k 10 k 20 k Procedure: 704619 Date: 21. Apr. 1998 Signature: Frequency Hz Frequency Hz BC-0261-11960415e Fig.2 Calibration chart supplied with the 4197 microphone pair. The measured microphone phase matching and individual microphone free-field responses are given 2 operate on a polarization voltage of 200 V. The probe sets have cables termi- nated with a single 18-pin plug, and are specially designed for direct con- nection to dual-channel analyzers. The useful free-field frequency range for the 3583, using the various microphone and spacer combinations, is from 1/3-octave centre frequencies of 20 Hz to 10 kHz. For Type 3584 the range is 20 Hz to 6.3 kHz. The actual frequency range in practice depends on the difference between the pres- sure and intensity levels, that is, Pressure-Intensity Index (see section on Frequency Range), which is de- pendent on the nature of the sound Fig.3 Remote control units field and the phase response devia- tion between the probe and processor channels. measured free-field frequency re- tosequence”, “Accept/Save” and sponse for each microphone. “Input Autorange” controls, and also The IEC 1043 standard distin- 1 ″ LEDs for overload, autosequence and guishes between Probe, Processor The /4 Type 4178 microphones averaging information, with direc- and Instrument and classifies them can also be mounted in a side-by-side tional information. according to the measurement accu- configuration using parts available racy achieved. There are two degrees separately. These include the side-by- ZH 0354 is available separately for of accuracy designated Class 1 and side mounting clip DK 1002 to sepa- use with Type 3583 and is specifical- Class 2. The Brüel & Kjær probe set rate the microphones by a distance of ly designed for use with Dual Chan- × complies with IEC 1043 Class 1, 12 mm, two adaptors (2 UA 0954) to nel Real-time Frequency Analyzer which has the most stringent toler- provide well-defined microphone Type 2133. ance requirements. Note, however, venting when using this configura- that the IEC standard only specifies tion, and two Type 2670 preamplifi- the frequency range from centre fre- ers which connect to the adaptors. Frequency Range Although this is not the optimum quencies of 50 Hz to 6.3 kHz in 1/3- octave bands.
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