How Loud and What Sound

There are many challenges facing us as quieter cars come onto the market in greater numbers. What do I mean by this?

• Safety - since many new vehicles are almost completely silent when at rest or just starting to move, we pedestrians and cyclists won't be able to rely on our hearing to know that a car poses a danger to us.

• Intellectual - assuming cars should produce some kind of warning noise, what kind of noise should it be, how loud must it be, at what speeds should it be broadcast, and from what location on the car should it come? What control should an owner have compared to the manufacturer? Should a local municipality, state or a nation set the sound standards?

Should cars sound like the old Jetson's flying car?



We don't want our world filled with beeping, howling, growling, shrieking noises, but we don't want to get run over, either.

Automotive News described some of the European manufacturers as designing sounds that are "futuristic" and "jet-like." Some of the tones will increase in pitch and volume as the car speeds up. The sounds are different when cars are moving forwards or backwards.

Here's the Nissan Leaf:



I think it sounds terrible, even if Nissan says they have been working for 3 years "to develop a new type of audio visibility ... for those visually-impaired." Huh? Say what? Couldn't they have said audibility? It's a perfectly suitable word we already had in the toolbox.

Some manufacturers are seeking a "brand tone" tone to audibly present their cars in the most favorable way. Just as we like a nice smell in a new car, wouldn't we be pleased if our car has the nicest sound around?

One clever entrepreneur thought to offer EVTONES, a website where he hopes future car buyers will purchase and download various "car tones" into their cars, as we do today with ringtones on our mobile phones. His site was based on some risky assumptions:

• people will want to customize their car's noise
• automakers will make such a system "open" to modifications (UNLIKELY)
• safety authorities will allow changes (NOT)
• the liability aspects of making changes will not be overwhelming (THEY WILL)

By the way, it's worth saying that this is not strictly an electric car issue, it applies to hybrids and to quiet internal-combustion vehicles too.

What does this have to do with math? Sound. Volume. Frequency. Direction. Degrees of peripheral vision. Peripheral hearing. Money. Meeting Deadlines. All involve math.

• Hyundai delayed their hybrid in the US to take out a switch allowing owners to silence the noise, in response to a US law.
• Nissan delayed their Leaf electric in the UK to put in a switch allowing owners to silence its noise, in response to a UK law.

If you want to read more about it:


Wikipedia article on vehicle warning sounds

The Pedestrian Safety Enhancement Act of 2010 Click the link and download the pdf file.