Flying Car More Economical Than SUV

fusion812 writes "The M400 needs 35 clear feet to take off but thanks to its 770 hp engine can whiz to 365 mph - cruise control kicks in at 326 mph - and climb at 6,400 feet per minute. You may hear it before you see it: it emits a rather noisy 65 dba at 500 feet. Interestingly, with a fuel consumption of 20 miles to the gallon on the road, it's rather more economical than a Sports Utility Vehicle (SUV) and looks positively eco-friendly compared to a Hummer."

Comments

Re:WTF?

[Reverberant]

It's 65dBa at 500 feet. Since loudness decreases/increases quadratically

Warrax_666 makes a good point. (and to answer your question, sound usually decays at a rate of 10*log10(D/Dref) for line-sources and 20*log10(D/Dref) for point sources, although ground absorption and atmospheric absorption can cause more rapid attenuation in certain circumstances).

65 dBA at 500 feet translates to 85 dBA at 50 ft (assuming point source propagation, which is probably reasonable).

For comparison:

• Locomotive idling @ 50 ft: 80 dBA
• Bus idling @ 50 ft: 75 dBA
• Automobile @ 50 ft, 50 mph: 70 dBA
• Diesel locomotive @ 50 ft, 50 mph: 92 dBA
• Transit train (electric) @ 50 ft, 50 mph: 86 dBA
• Train horn @ 50 ft: 105 dBA

So in short, it's louder than cars traveling at 50 mph, but not as bad as a train horn. Also keep in mind that if the flying car is, well, flying, there won't be anything to shield the noise from the vehicle, and that may make it louder than normal cars in practice.