Measurement moments

To celebrate our anniversary, we are sharing funny, interesting and unusual stories relating to sound and vibration.

Do you have a sound and vibration story to share? Please send it to us.

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A cake to remember

Congratulations to Anne and Phil Budd for four years of marriage!

We don’t normally celebrate wedding anniversaries at Brüel & Kjær, but when Anne Carey (Director, New Acoustics) and Phil Budd (Senior Acoustic Engineer, Linn Products) married in the UK on 25 April 2009, the groom organised a rather unusual wedding cake in honour of the business through which they met.

Phil’s surprise acoustic-style wedding cake was topped with the traditional bride and groom figures, except the bride wore a dress modelled on Brüel & Kjær’s sound level meter - Type 2260 Investigator - and the groom’s trousers were in the style of Linn Product’s Klimax 350 speaker.

All the best to the harmonious couple, and congratulations on a very tasteful cake!
Amphibious vibration detectors

The Iberian midwife toad lives most of its life in a hole in the ground, and little is known about them except that they are sensitive to vibrations in the substrate. But a research team in Spain led by Dr. Rafael Márquez is collaborating with colleagues in the US and Chile to see just how sensitive they are.

The team uses Brüel & Kjær sound level meters and calibrators to measure sound pressure level, as well as a Hand-held Exciter Type 5961 to calibrate their geophones, in order to measure the toads' detection thresholds for vibrations.
Tennis grunt-o-meter

The grunting of tennis players has never been far from the headlines ever since Monica Seles apparently ‘invented’ the modern tennis grunt back in 1989.

But by 2009, grunt-criticism had reached a peak, with widespread calls for point deductions and decibel limits. And as a Time magazine article pointed out, journalists at that year's Wimbledon Championships were even wielding Brüel & Kjær sound level meters to capture the noise levels of the loudest female players. Although we aren’t sure how well trained UK tabloid journalists are in the science of decibel scale-selection, their results consistently show that Maria Sharapova holds the dubious honour of top grunter, with a claimed 105 db.

Caroline Wozniacki (shown here) is one of the many players opposing grunting.
Brüel & Kjær Airlines

Yes, there was indeed a Brüel & Kjær 'airline', which was instrumental in creating foreign markets for the expanding Danish company.

Operated between 1963 and 1992 by Dr. Per Brüel the fleet grew to include two Piper Aztecs, two Beechcraft King Airs, and the Piper Navajo Chieftain - shown here being loaded for worldwide delivery.

The aircrafts made trips across the Atlantic and all around the world, including to Thailand, Russia and Africa, and were even pushed into service as airborne microphone testing platforms during the development of a surface microphone for the Concorde programme.
Kids shout louder than a jet

Everyone knows that teachers have a challenging job, but a shouting contest in the UK showed just how noisy kids can be when one youngster yelled louder than a jumbo jet.

A 7-year-old named Theo Harrison won the competition with his ear-splitting 137-decibel shout. This is 7 decibels higher than the threshold of pain and 17 decibels louder than the front row of a rock concert. Even a shout from all the other kids together couldn’t beat Theo’s result. Read more here.
Is that a submarine or a herring fart?

Our hydrophones have measured many different sea creatures over the years, but one Swedish team even used them to win an Ig Nobel prize after the Swedish government became concerned that underwater recordings they had made showed submarines in the waters off Sweden.

Two marine biologists, Magnus Wahlberg and Haaken Westerberg, were able to confirm that the sounds were in fact from an animal, before discovering that the sounds were made by herrings communicating with each other – by letting air out of their swim bladders and making a farting noise.

You can hear the sounds for yourself on a National Geographic video

And here is a video of Marc Abrahams, the organiser of the Ig Nobel prize, explaining the story
Returning song to Hagia Sophia

This week we've found a Measurement moment from the city where East meets West. Istanbul’s famous Hagia Sophia was designed as a gigantic amplifier, but is now a museum where singing is no longer heard.

As part of the ‘CAHRISMA’ EU project to identify, revive and conserve architectural heritage in a new way, the team from Odeon mapped the room acoustics of the structure with the help of the
Brüel & Kjær OmniPower Sound Source shown here. They were subsequently able to record some overtone singing featuring the simulated acoustics of the famous building.

You can hear the strikingly realistic acoustics here
Ensuring the crispiness of crisps

How can you use Brüel & Kjær technology to ensure the crispiness of crisps. Mount an accelerometer on them perhaps?

When the BBC’s Jimmy Doherty visited a Walkers crisps factory in the UK, he learned all about the science of crisps, which by their very name need to be crispy.

Many years of research has seen Walkers comprehensively analyse ‘crunch’, and they’ve concluded that how hard we have to bite, and how quickly we hear the crunch sound is really important to how much we enjoy eating crisps. And what do they use to listen to the crunch? You guessed it – a Brüel & Kjær microphone.
Why is everything green?

Brand new racks of LAN-XI modules look sleek with their tough green front panels, but as many people ask, “why is it that everything Brüel & Kjær is green?”

The answer is simply that when the wooden casings of our very first instruments were being painted in an old Danish army workshop, the surplus paint that came to hand most easily was green, and the unmistakeable Brüel & Kjær colour has stayed the same ever since.
Talking to bees on the dancefloor

For hundreds of years, people have known that bees show each other where to find food, but now it is possible for humans to tell bees where to fly.

Knowing that they communicate through dancing, Professor Axel Michelsen and his team at Denmark’s Odense University used two miniature probe microphones to measure the acoustic near-field of ‘talking’ bees. The researchers found that vibrations in the air stream behind the bees' wings contained the information that the insects were listening to.

Using these findings, the researchers constructed a small mechanical model to simulate bee communication movement, and have successfully instructed bees to travel specific distances and directions.
Solving the mystery of why cats purr

Ever since the Egyptians started worshipping the cat, philosophers, scientists and cat lovers have wondered why they purr.

Sure cats purr when they are content, but they also purr when severely injured, frightened or giving birth, and veterinary surgeons have observed how relatively easy it is to mend the broken bones of cats compared with dogs.

Using miniature accelerometers weighing a mere 0.14 gram, the purring frequencies of cheetahs, pumas, servals, ocelots and domestic cats were found to fall within the range of a multitude of therapeutic frequencies, and all had frequencies ±4 Hz from the entire repertoire of low frequencies known to be therapeutic for many ailments.

Frequencies of 25 and 50 Hz are the best, and 100 Hz and 200 Hz the second best frequencies for promoting bone strength. Exposure to these signals elevates bone strength by approximately 30%, and increases the speed at which fractures heal.

Read article
A quiet start

Brüel & Kjær began life in an old army workshop when Per Brüel and Viggo Kjær made the world's first acoustic analyzer.

From there, the production facilities have moved to the modern buildings of today via Viggo Kjær’s kitchen table and a dressmaker’s workshop – where no noise was permitted before 10 a.m.