Car Stereos: decibels, air raid siren, car audio competition

Question
Hi, I had used a decibel meter on my car's sound system and it read 129.3 i was just wondering if you could explain to me how loud that is?

Answer
Hi Justin,

"How loud is this?" is a hard question to answer, but I'll try to give you some perspective.

Here's a decibel level comparison chart, that will give you some idea of sounds that are comparable to your volume level:

http://www.esoundproof.com/Screens/Basics/Academy/Sound%20Measurement/Decibels/d...

Your car is in about the "air raid siren" or "jet engine takeoff" range.  The 120-130dB range is generally considered the threshold of pain for human hearing.  It's definitely not a volume range to which you'd want to be exposed very long if you value your hearing.  

How does it compare in terms of car audio systems?

Well, here's the current list of all time records in the IASCA's IdbL classes.  IASCA is one of the best-known car audio competition organizations, and IdBL is their "maximum volume" contest):

http://www.iasca.com/content/Stats/05idbl/alltimeworldrecords.aspx

I don't know how your car's audio system fits into the competition categories, but if you're like most amateur car audio owners, you'd probably fall into the "Rookie 2" class.  Rookie 2 would include vehicles with stock electrical systems and alternators, a single battery in the factory location, and a pair of 12" subs.  (If you had a pair of 10" subs, you'd probably fall in the Rookie 1 class).

The world record for a Rookie 2 system is about 20 dB higher than your measured decibel rating.  The decibel scale is logarithmic, not linear.  That means that each 10dB increase in sound level is equivalent to doubling the apparent volume; ie, 140dB is twice as loud as 130dB, and 150dB is twice as loud as 140dB.  So the world record volume level, for a system that includes stock electrical components and a pair of 12" subs, is about four times as loud as your system.

All in all, if your measurement is accurate, I'd say your system is more than loud enough for normal musical listening, but not quite loud enough for serious autosound competition.  Of course, your SPL meter and testing methods may not be as accurate as those used in dB competition judging.  If you're interested in competing as a hobby, then I'd suggest finding a local car audio "sound-off" and having your car measured.  You might also be able to have this done at a local shop that caters to car audio competitors.  

Hope this helps!

Brian