dB drag racing

dB drag racing is a competition rewarding the person who can produce the loudest sound inside a vehicle. The "dB" means decibels of sound pressure level (SPL). In these competitions, SPL of 155 dB can be reached, and it is not unheard of to see 160+ dB as well.

Competitive vehicles can range from a small vehicle with a single amplifier and subwoofer up to a large van with 72 amplifiers putting out 130,000 watts to nine sub-woofers (15 in.), powered by dozens of car batteries and with upgraded electrical wiring and alternators.

There were 10,000 competitors in 2003 and 300 "races". U.S. National Championships were held in Tennessee.

During a competition, the vehicle must be driven 20 feet. Nobody is allowed to sit in the vehicle during trials because injury would be certain. The vehicles are sealed tight to maximize containment of the sound energy for the decibel level meter. The competitor stands away from the vehicle with an on/off switch control while a computer voice announces the stages for the "races". The test tone consists of a very short resonating tone between 30 Hz and 70 Hz, called "the burp".

The current loudest car has been recorded at 180.5 dB. For comparison:

• 400dB -- Volcanic eruption
• 200dB -- Rocket engine at 30 m
• 183dB -- Blue whale humming at 1 m
• 163dB -- Windows break
• 150dB -- Jet engine at 30 m
• 130dB -- Threshold of pain; train horn at 10 m
• 120dB -- Rock concert

The perceived loudness doubles with every 10dB increase, so 178.9 dB is more than 32 times as loud as a rock concert (nearly $2^{6}=64$), and nearly 8 times as loud as a jet engine at 30 m.

Direct comparisons, however, can only be made with the same measurement techniques, and the same weighting scale.

Sources

• Official DB Drag Racing Website
• "This American Life" radio broadcast 2004-12-11 ("Auto Show").
• Extreme SPL Racing
• CNN report