Brüel & Kjær (Sound and Vibration Measurement A/S) is a Danish multinational engineering and electronics company headquartered in Nærum, near Copenhagen.

[citation needed] The most notable products and technologies developed by the company include: Brüel & Kjær (now HBK) provides tools to overcome noise and vibration challenges.

[7] Main customers in this field are Airbus, Aircraft Strength Research Institute, Boeing, EADS, Eurocopter, Rolls-Royce, and Sukhoi.

[9] The company provides products that aid preventative maintenance and manufacturer-specified checks to prolong the health of engines.

Real-time multi-analysis capabilities 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.

It offers high-temperature accelerometers that can monitor the health of operational machinery 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.

Furthermore, it provides monitoring systems for engines and gearboxes with permanently placed HUMS sensors and signal conditioners for extreme environments.

[8] 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, 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.