z Products & services
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APRIL 2015
AEROSPACETESTINGINTERNATIONAL.COMFifteen years into the 21st century, sound
and vibration measurement and analysis
is an essential component of aerospace
product development. The shortening design
and development timeframes of modern
aerospace programs demand ‘right first-time’
engineering. Whether the challenge is ensuring
structural integrity and product safety,
performing exterior noise analysis such as
flyover testing, or confirming the integrity of
aircraft gas turbines, the technology being
used today had its start nearly 80 years ago
outside Copenhagen, Denmark. It was the
brainchild of Per V Brüel, who has just
celebrated his 100th birthday. He can now look
back on a century in which he played multiple
larger-than-life roles: engineer and inventor,
founder of a major global corporation and pilot
who personally pioneered new markets.
INITIAL BREAKTHROUGHS
As a young engineer with a recent PhD in
acoustics from Danish Technical University
and a passion for innovation, Brüel made his
initial breakthroughs in the late 1930s and
early 1940s with the development of the
world’s first acoustics analyzer and the first
commercial piezoelectric accelerometer (Type
4303). “I was able to make the first acoustics
analyzer in the world,” he says. “No one had
ever made anything like that before. We made
two copies, and it became our first commercial
instrument when Viggo Kjær and I started
Brüel & Kjær.”
This early work was the foundation for
many of the products that followed. It was
new territory, but as a pilot himself, Brüel
could see its importance to the future of
aircraft development. These insights were the
genesis of a global company – Brüel & Kjær’s
first production site was rented space in a
dressmaker’s workroom. The company that
Per Brüel and Viggo Kjær founded is today
the world’s largest specialist in sound and
vibration solutions. Its product line grew to
include transducers, data acquisition systems
and data analysis systems, as well as a
comprehensive range of electrodynamic
shakers designed for vibration testing of
devices of practically any size, from a
semiconductor component to a complete
satellite system.
Even in the early days, a main objective
was to use the instruments to measure and
reduce vibration and noise levels, both of
which are vital concerns in the aircraft
industry. “Even then we could see that noise
is one of the biggest problems of our time- it affects millions of people every day,”
says Brüel. It became increasingly clear that
sound and vibration instruments could help
manufacturers improve the safety and comfort
of airline passengers worldwide by enabling
them to see how their products would stand
up to real-world conditions.
Brüel pioneered the development of
products such as a revolutionary sound-level
recorder and microphones that set a new
standard for accuracy and stability. A single
example is the special microphone (Type 4193)
developed to measure and analyze the
N-Wave generated from Concorde’s sonic
booms. These products were the forerunners
of the complete aerospace testing and
analysis systems and comprehensive applied
solutions that the company supplies today.
OPENING NEW FRONTIERS
On Brüel’s 100th birthday, it is interesting to
reflect that one man’s passion for overcoming
engineering challenges has led to sound and
vibration innovations throughout the entire life
of aerospace industry products, from modeling
an early design, to manufacturing the product
and maintaining its operation. Today, sound
and vibration testing contribute not only to
safer, more comfortable air travel and to
reducing airport noise, but also to advancing
space exploration. Brüel & Kjær data
acquisition and vibration test systems have
been used to test NASA’s Mars Curiosity rover,
Astrium’s satellites and the ESA’s Rosetta
space probe, which recently landed on a
comet. Also, Brüel & Kjær accelerometers
were present on the legs of the lander, Philae,
to ‘listen’ to its landing on the comet.
It shouldn’t be surprising that Per Brüel was
the source of sound and vibration advances
that continue to help advance aerospace
development. His engineering passion was
equaled by his enthusiasm for flying. He was
licensed in Denmark to fly single- and multi-
engine planes as well as gliders. From 1957 to
2000, he logged 9,476 hours of flight in more
than 20 aircraft. Many of those hours were on
business trips, opening new markets and
pursuing new challenges throughout Europe
and as far afield as Russia and China, piloting
company airplanes that were humorously
referred to as B&K Airlines. It seems only right
that his engineering insights are playing a part
in pushing back the frontiers of space. za century of innovation
Company founder, innovator and leader in the aerospace testing
industry Per V Brüel celebrated his 100th birthday on March 6, 2015
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Per V Brüel flying
(above right), and
measuring airport
noise in 1971 (right)