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Let’s Reminisce: From rattletrap to quiet
By Jerry Lincecum
Jun 28, 2014
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As a boy I rode in my grandfather’s steel-tired wagon a few times, and on a gravel road it was so noisy that you couldn’t carry on a conversation.  In that era the term “rattletrap” was commonly used in describing the older cars and pickups that many people drove.  Even when you bought a new pickup, driving it on gravel roads and across pastures would soon give it plenty of rattles.

What brought this to mind is a TV commercial I saw recently for the 2014 Chevy Silverado pickup, which devoted 30 seconds to boasting about the lack of noise in its cabin.  A quiet ride used to be a bragging point exclusive to the luxury-car world, a sign of a car's refinement. But nowadays the quest for silent rides has moved into the mainstream of cars and even pickup trucks.

To accomplish the quiet Silverado, General Motors added enhanced baffling inside the doors and thicker, better-sealed windows. To cut down wind noise, their engineers inlaid the cab doors so their top edges no longer curve over the rooftop.

A decade ago, most interior noises couldn't be heard because of the engine and road noise.  Now you may notice even the tiny motor that runs the vent door that opens and closes in a heater or air conditioner.

Car noise is becoming a big problem for the manufacturers. That's because more owners are bringing in their new vehicles for repairs after hearing noises -- even when nothing is really wrong. These trips drive up warranty costs and hurt the reputation of a car's quality.

It's frustrating for the owner of a new car to come back and report a sound, only to be told by the dealership that it's “normal” and there is nothing they can do about it.  To reduce the frustration, carmakers are creating “Quiet Labs.”

One company spent more than a million dollars to develop a sound-testing facility, which includes two acoustic rooms built on shock absorbers to stop noise from bleeding in through the ground.

They have compiled a database of more than 1,000 noises caused by the motor and blowers inside a car's heating, ventilation and air conditioning (HVAC) unit, ranging from low throaty rumbles to a high-screeching whistle or chirp tone. The database is used with computer software to help identify which sounds need muffling.

To develop a quiet blower for the HVAC system, for example, engineers have tried geometrically rearranging the blower's blades. Imagine a hamster wheel lying on its side spinning around in the middle of a fat soup can. To reduce the sound they changed the distance between the blades on which the hamster's feet run.

Noises and sounds are always going to be produced by a car or truck.  The trick is turning down or masking the ones that the human ear doesn't like. It's a paradox of today's advanced car design: The more automakers succeed in muting sounds coming from outside, the more drivers are hearing the annoying little chirps, rattles and drones on the inside.

Few people know or care about the noisy wagons or rattletrap cars we used to be happy with.

Dr. Jerry Lincecumis a retired English professor who now teaches classes for older adults who want to write their life stories. He welcomes your reminiscences on any subject. Email him at jlincecum@me.com.