Harman Patil (Editor)

Brüel and Kjær

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Type  (Private company)
Revenue  DKK991 million (2011)
Headquarters  Nærum
Founded  28 November 1942
Area served  Worldwide
Number of employees  1,150
Founder  Per Vilhelm Brüel
Parent organization  Spectris
Brüel & Kjær
Industry  Engineering Sound & Vibration
Key people  Lars Rønn (Managing Director)
Products  Sound Measurement, Vibration Systems

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:

  • 1940s – Precision measurement instruments including radio frequency analysers and Geiger counters.The first Brüel & Kjær instrument produced was Type 2401, a vacuum tube voltmeter. The success of the company started with Type 2301 in 1949. Since then it has been updated a number of times. The latest version, Type 2307, was introduced in 1972. In 1943 Brüel & Kjær launched Type 4301 - the world's first Charge Accelerometer, thus entering the field of vibration measurement.
  • 1950s – Sound and vibration measurements, including development of logarithmic level recorders, signal generators and frequency analyzers.
  • 1960s – Measurement microphones, preamplifiers and calibrators, along with IEC standardised precision sound level meters.
  • 1970s – Parallel analyzers, including the world’s first analyzer to use digital filters.
  • 1980s – The first commercially available instrument for sound intensity measurement, and expansions of the range of instruments; for example, dual channel FFT analyzers.
  • 1990s – Multichannel and multi-analysis systems, including acoustical holography array systems.
  • 2000s – Surface microphones and LAN-XI modular data acquisition hardware. New technologies such as TEDS, Dyn-X, REq-X.
  • Aero engines

    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.

    Brüel & Kjær's main customers in this market include

    Airbus, Aircraft Strength Research Institute, Boeing, EADS, Eurocopter, Rolls Royce, and Sukhoi.

    Some of Brüel & Kjær's space customers are shown on Brüel & Kjær's website here

    Acoustic stealth discretion

    Acoustic stealth and discretion play a vital role in ship and submarine operations. Brüel & Kjær supplies systems for noise signature management: acoustic ranging of submarines and surface ships; noise source investigation during design and build; and for acoustic trials and self-noise monitoring during operations. Brüel & Kjær also supplies systems for underwater acoustics, shock testing, noise and vibration testing and structural dynamics testing.

    Identifying noise sources

    Brüel & Kjær offers products that cover a wide range of acoustic customer-oriented solutions, ranging from simple sound level measurements to the most sophisticated microphone array systems using advanced algorithms and hardware. These solutions 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 e.g., ramp noise or sonic booms, microphone calibration systems and more.

    Maintaining operational integrity

    The company provides products that aid preventative maintenance and manufacturer-specified checks to prolong the health of engines. These products take the form of real-time multi-analysis capabilities that reduce the number of run‑ups/‑downs and gather more data faster for analyses ranging from simple pass-fail overall measurements to in-depth advanced analysis in order to maximize the up-time of aircraft. Brüel & Kjær offers products like high-temperature accelerometers that can monitor the health of operational machinery. The company provides solutions for maintenance, repair and overhaul tasks such as balancing, trim balancing, on-ground engine vibration checks, vibration diagnostics and re-run production tests using real-time analysis. In addition, systems are available for monitoring equipment, engines and gearboxes with permanently placed HUMS sensors and signal conditioners for extreme environments.

    Environmental noise impact testing and monitoring

    Brüel & Kjær supplies systems for occupational health, helmet/cabin/cockpit noise assessment, acoustic and human vibration monitoring, urban noise monitoring and noise-mapping of vehicles in order to test and monitor the environmental noise impact, and to look for ways of reducing environmental noise impact on armed forces personnel and local communities. These activities include: Helmet/cabin/cockpit noise assessment, human acoustic and vibration monitoring, urban, airport, industrial and construction noise monitoring, and vehicle noise mapping.

    Wind tunnel testing

    Since wind tunnel and test track measurements are often the only way to recreate real-world conditions for model and mule car testing, and are also a good method of validating simulated model data, Brüel & Kjær tries to provide measurement devices that focus on these types of tests, providing specialised solutions for specific needs so that they can perform vehicle pass-by noise contribution studies for cars, trucks and trains, location of high-frequency engine noise sources, and wind-tunnel measurements. Surface microphones mounted on the exterior of a vehicle measure the pressure fluctuations at different positions of the vehicle without drilling holes. Beamforming can be used for noise mapping at a distance from large objects. The data for all points is acquired in a single measurement, saving time and effort.

    Setting targets

    Brüel & Kjær’s sound quality solutions provide the tools for recording, analysing, auditioning, dissecting, and synthesising sounds. The range enables the use of simulation models and test data to develop modifications to improve the sound quality and to achieve the ultimate objective of designing the desired sound characteristics into the product.


    Brüel & Kjær has developed an NVH tool for surreptitious recording and analysis called SoNoScout. It can be carried in the tester’s pocket on a train or bus without distracting the passengers or in a competitor’s vehicle where it can be combined with a GPS unit to generate a map of the test route, measure speed and even generate an RPM profile. The software runs on a PDA with microphones binaurally mounted on a headset for quick recording.

    Telecom and audio

    Brüel & Kjær provides products to telecom and audio customers – from transducers to measurement, analysis and reporting for evaluation of electroacoustic devices:

  • A dedicated platform that includes couplers, microphones, amplifiers, analyzers, calibrators, sound sources, and measurement and analysis software.
  • Specialised standards-based telephone test systems for all communication technologies, including GSM, UMTS, AMPS, CDMA, W-CDMA, Bluetooth and VoIP.
  • Exceptional ear and mouth simulators.
  • Advanced material testing, modal analysis, sound quality and environmental solutions for development, benchmarking, production and quality assurance testing.
  • Organisational developments

    In 1992 Brüel & Kjær was sold to AGIV (a German holding company), and split into a number of separate companies:

  • Brüel & Kjær Sound and Vibration Measurement A/S (the core sound and vibration market)
  • Brüel & Kjær Vibro (machinery condition monitoring)
  • B-K Medical (ultrasonic medical diagnostic instruments)
  • Innova Air Tech Instruments A/S (gas analysis instrumentation)
  • Danish Pro Audio (studio microphones)
  • After the division of the company, a number of former employees left to form G.R.A.S. Sound and Vibration. AGIV included the Brüel & Kjær split companies within its Spectris Division, which comprised Brüel & Kjær, Hottinger Baldwin Messtechnik GmbH (HBM), and BTG Instruments GmbH. In July 2000, the Spectris Division was sold to Fairey Group Ltd. (a British Company), and in May 2001, Fairey Group changed its name to Spectris Plc.

    Brüel & Kjær acquired LDS Test & Measurement in January 2009, and, in February 2009, acquired Lochard Ltd.

    Similar Companies / Competitors

  • Sensidyne Sound & Vibration Instruments
  • References

    Brüel & Kjær Wikipedia

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