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Abstract

PRIMARY PRESSURE CALIBRATIONS OF BRāEL & KJAER HALF-INCH MICROPHONE TYPES 4134M AND 4134 AT FIVE EEC STANDARDS LABORATORIES ARE COMPARED. AT FREQUENCIES UP TO 10 KHZ, THE SENSITIVITY LEVELS DETERMINED BY THE LABORATORIES SPANNED 0.14 DB AND 0.2 DB FOR THE MICROPHONE TYPES 4134M AND 4134 RESPECTIVELY. AT 20 KHZ NPL REPORTED RESULTS BETWEEN 0.2 AND 0.3 DB HIGHER THAN THE OTHER LABORATORIES. NORMALISING THE RESULTS TO COMMON VALUES OF MICROPHONE TOTAL EFFECTIVE VOLUME AND ACOUSTIC IMPEDANCE REDUCED THE DISCREPANCIES AT LOW FREQUENCIES CONSIDERABLY, BUT LEFT THE HIGH FREQUENCY RESULTS ALMOST UNCHANGED. RESIDUAL DISCREPANCIES MAY POSSIBLY BE RELATED TO DIFFERENCES IN THE MEASUREMENT OF THE ELECTRICAL TRANSFER IMPEDANCE OF THE COUPLED MICROPHONES.

Additional information

Authors: TORR G R, NATIONAL PHYSICAL LABORATORY, TEDDINGTON, MIDDLESEX, UK;JARVIS D R NATIONAL PHYSICAL LABORATORY, TEDDINGTON, MIDDLESEX, UK, NATIONAL PHYSICAL LABORATORY, TEDDINGTON, MIDDLESEX, UK
Bibliographic Reference: EUR 11751 EN (1988) MF, PP 97, ECU 4.00, BLOW-UP COPY, ECU 12.50, AVAILABILITY: EUROFFICE, LUXEMBOURG, BP 1003, GDL
Availability: Can be ordered online
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