Brüel & Kjær (Sound and üelKjæVibration Measurement A/S) was a Danish multinational engineering and electronics company headquartered in Nærum, near Copenhagen. It was the largest producer in the world of equipment for acoustic and vibrational measurements Brüel & Kjær is a subsidiary of Spectris.
Brüel & Kjær was founded by Per Vilhelm Brüel (6 March 1915 – 2 April 2015) and Viggo Kjær (5 June 1914 – 25 July 2013) on 28 November 1942, which met while studying at The Polytechnic School in Copenhagen (now the Technical University of Denmark). After accomplishing their M.S. degrees in 1939, they established a company which specializes in the development of acoustic measurement instruments.
Holger Nielsen joined the company as a third partner in 1945 until his death in 1978.
Products
The most notable products and technologies developed by the company include:
1940's – Precision measurement instruments including radio frequency analyzers and Geiger counters. Type 2401, a vacuum tube voltmeter, was the first instrument produced. Type 4301, launched in 1943, was the world's first charge accelerometer, while Type 2301 marked the success of the company in 1949. Since then it has been updated a number of times: the latest version, Type 2307, was introduced in 1972 1950's – Sound and vibration measurements tools, including logarithmic level recorders, signal generators and frequency analyzers 1960's – Measurement microphones, preamplifiers and calibrators, along with IEC standardised precision sound level meters 1970's – Parallel analyzers, including the first analyzer using digital filters 1980's – The first instrument for sound intensity measurement; dual channel FFT analyzers 1990's – Multichannel and multi-analysis systems, including acoustical holography array systems 2000's – Surface microphones, LAN-XI modular data acquisition hardware and TEDS, Dyn-X, REq-X technologies
Markets
Aero engines
Brüel & Kjær (now HBK) provides tools to overcome noise and vibration challenges. These ensure the quality of new lighter material applications by modal testing and improving the quality and test efficiency in aero engines. Systems include those for development and measurement of new noise-optimised engines, acoustic lining designs and propagation code validation (engine duct modal analysis, far-field noise measurement, and acoustic panel in situ impedance measurement) It also supplies in-flight engine monitoring with flight-certified, high-temperature accelerometers.
Aerospace
Brüel & Kjær supplies data acquisition systems and vibration test systems (LDS) to customers in the aerospace industry, such as the LDS V994 shaker, used to test NASA's Mars Curiosity rover. Other systems have tested Astrium's satellite prior to launch, and performed qualification and acceptance testing, such as the integrated LAN-XI data acquisition systems used by the National Institute for Space Research in Brazil INPE. Main customers in this field are Airbus, Aircraft Strength Research Institute, Boeing, EADS, Eurocopter, Rolls-Royce, and Sukhoi.
Defence
Acoustic stealth discretion
The company supplies systems for noise signature management: acoustic ranging of submarines and surface ships; noise source investigation during design and build; acoustic trials and self-noise monitoring during operations. It also supplies systems for underwater acoustics, shock testing, noise and vibration testing and structural dynamics testing.
Identifying noise sources
Brüel & Kjær makes several products in audio measurement, ranging from simple sound level measurements to sophisticated microphone array systems using advanced algorithms and hardware. These products are provided for air-vehicle noise certification, exterior noise analysis such as fly-over testing using acoustic holography, beamforming, SONAH and high-temperature sensors, noise source identification to examine, for example, ramp noise or sonic booms, microphone calibration systems and more.