Here's a mind-blowing fact. That nice solid sound your vehicle's door makes when you slam it isn't real. It's just been engineered to sound solid because we have an expectation that's how it will sound.

James Ford told Mel Magazine that car companies started engineering that sound into doors ten years ago thanks to psychoacoustics. Psychoacoustics is the study of psychological and sensory responses associated with sound.

The bottom line is we expect a good solid door sound when we slam it shut. Because for years it wasn't sound engineering that caused that sound. The doors really made that sound. About ten years ago though added safety measures meant that manufacturers added bars into the doors to make them stronger. That changed how the doors sounded when we slammed them.

Enter psychoacoustics. What's one of the things all of us do when we're looking at a new car? We shut the car's door, a lot of times, right in the showroom of the car dealer. This is according to Jonathan Berger, a music professor at Stanford University’s Center for Computer Research in Music and Acoustics.

Here's what a study performed by his psychoacoustics found out about the noise our car doors make when slammed:

Our hypothesis that a low-frequency thud with a short duration and no trailing sound would be perceived as the most ‘high class’ vehicle was correct in terms of frequency — a low, soft thud seems ‘fancier’ than a high frequency one,” he explains. “But to our surprise, the ‘short duration and clean tail’ didn’t hold. The sound with the highest perceived value had an after sound — imagine a ‘ker-chunk.

Psychoacoustics in vehicles doesn't stop with the slam of a car door either, they also engineer the click of the locks. Someday they may even use psychoacoustics to mimic the noise of an engine. I mention this, because one of the things that surprise people when driving a hybrid car, is the fact that the engine shuts off at lights. I'm not saying that'll happen, it hasn't yet. But it's not out of the realm of possibility.

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