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Page last updated at 16:34 GMT, Friday, 8 July 2011 17:34 UK

How engineers create artificial sounds to fool us

A man recording the sound of a car door
The sound of a car door has evolved as car technology develops

Many of the sounds we hear every day are entirely fabricated by engineers to persuade us to buy things.

Hundreds of items have their acoustics deliberately tweaked to make us happy, according to Trevor Cox, professor of acoustic engineering at the University of Salford.

What you hear when you close a car door, for example, can be traced back to changes in the car manufacturing industry about 10 years ago.

"What manufacturers realised is when you go to see a car in a showroom you don't hear the engine first," says Prof Cox. "What you hear is the sound of the door opening and the sound of the door closing.

"It's a really important first impression sound."

But when manufacturers had to put extra bars in their side doors to comply with new safety standards the sounds of their doors started to change.

To compensate for the added weight they had to make other parts of the car lighter and took weight from the catches and door mechanisms.

As a result, doors no longer made a satisfying clunk but had a tinny sound.

"They thought 'How can we go about re-engineering the sound so it sounds more expensive and more high quality?'," explained Prof Cox.

Manufacturers then started experimenting with different sound effects.

Dampeners were introduced into the door cavity to muffle the tinny effect and engineers altered the locking mechanism to make just the right sort of click.

'Potato Potato'

A group of motorbikers on Harley Davidsons
Harley Davidson's iconic grumble is often described as the 'potato-potato' sound

The engineering of everyday sounds has since spread to other industries.

The shutter noise on a digital camera is just one example of a sound entirely fabricated to make a modern gadget imitate older technology.

"I find myself drawn to digital cameras with a very strong shutter sound on them," says BBC technology correspondent Clark Boyd.

"What is clear is that we associate certain sounds with the quality of a product."

In some cases sounds are engineered to do more than just please or fool the consumer.

As in the case of the electric car, they are created in the interest of safety.

Nissan's new electric vehicle has a speaker fitted under its bonnet and a synthesiser in the dash to generate engine noise.

Likewise, the silent ENV hydrogen-powered motorbike is fitted with an artificial roar to warn road users it is approaching.

Indeed the sound of a motorbike engine is something that some manufacturers have been keen to protect.

In 1994 the iconic motorbike makers Harley Davidson began an application to trademark the distinctive chug sound of their products.

They claimed that Japanese manufacturers had mimicked the sound of their renowned V-twin engines.

The case went on for six years and in 2000 Harley Davidson dropped the application, claiming they had won in the court of public opinion.

"One of the funny thing about these technologies is how some of the old sounds and imagery lives on," said Prof Cox.

"When you drive around Britain, if you look for the sign for a level crossing, it's a steam train - but the last time I saw a steam train was many years ago.

"Or if you go to your computer and look at the save sign, it's a floppy disk. How many people are saving on to a floppy disk nowadays?"

In a similar way manufacturers of cars, phones and cameras are merely responding to their own archaic ideas of how things should sound.

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