Brüel & Kjær

Brüel & Kjær (Sound and Vibration Measurement A/S) is a Danish multinational engineering and electronics company headquartered in Nærum, near Copenhagen. It is the world's largest manufacturer and supplier of sound and vibration measurement equipment, systems and solutions, Brüel & Kjær is a subsidiary of Spectris which has annual sales of £1.1bn and employs around 7,500 people worldwide across its four business segments

Brüel & Kjær was founded by Per Vilhelm Brüel (b. 6 March 1915 - d. 2 April 2015) and Viggo Kjær (b. 5 June 1914 - d. 25 July 2013) on 28 November 1942. The two men met while studying at The Polytechnic School in Copenhagen (now the Technical University of Denmark). After receiving their M.S. degrees in 1939 they decided to start a company developing instruments for acoustic measurements. Holger Nielsen joined the company as third partner in 1945, and was with the company until his death in 1978.

Some of the products developed over 70 years include:

Brüel & Kjær 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 engine/ acoustic lining designs and propagation code validation (engine duct modal analysis, far-field noise measurement, and acoustic panel in-situ impedance measurement) Brüel & Kjær also supplies in-flight engine monitoring with flight-certified, high-temperature accelerometers.

Brüel & Kjær supplies products like data acquisition systems and vibration test systems (LDS) to many customers in the aerospace industry such as its LDS V994 shaker, which was 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.