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Top Fuel Dragster Noise measurements

Discussion in 'The Okie Corral' started by Cancer, May 24, 2010.

  1. Cancer


    Jul 12, 2007
    I attended the NHRA Summernationals Drag Races in Topeka Kansas, and I did some sound pressure level (decibels, dB SPL) measurements for fun. Most of us know that V8 Top Fuelers (TF) generate incredible exhaust sounds, but I wanted to make some objective measurements. We all like loud sounds, so I thought I'd share it you.

    I was using a Realistic (Radio Shack) Analog SPL meter, fast setting, A-weighted. I wish I had a nicer meter, but the Radio Shack works well, was affordable, and a better one would run over $300. I tried using C-weighting, but at launch, the meter was pegged beyond the meter's upper limit of 126 dB, so I set it to A-weight, which "ignores" the lower frequencies, and generates a lower reading, making these readings more valid. A-weighting is used in environmental noise testing. 120 dB is generally considered the threshold of pain in the ears, with hearing damage possible in minutes. 194 dB is the upper limit of sound pressure, beyond that is a shock wave, like an explosion, volcano or sonic boom.

    Sitting up in the stands near the starting line, about 75-100 feet away, I read 100 dB with two TF dragsters idling. Very nice exhaust lope, like an atomic popcorn popper. At launch, the needle jumped to 126 dB (but not pegged), and it was a wall of concussive pressure waves, shaking the grandstands enough to make your eyes blurry for a second. You feel it in your chest. Awesome. The nitromethane exhaust tastes "sweeter" than smokeless powder gun exhaust. I didn't wear earplugs though. Compared to shooting guns at ear level, the noise isn't extremely loud, but it's the fierce, continuous hammering of all 16 cylinders, and the frequencies are low enough that every exhaust pulse is felt in your body.

    I then went to the far-end of the track, about 800 feet down, and was about 150 feet from the track (as close as I could get). I measured 100 dB as the cars launched. There was a cool half second delay from when the exhaust flames shot out until you hear the noise. As the cars roared by, the needle hit 124 dB. It was fun to feel the wave of intense exhaust impulses approach and envelope you.

    I bet the measurements would be quite higher if I measured using a better C-weighted meter, probably high 130s. I'm certain the starting line crew is feeling 140+ dB noises.

    If I had to compare a gun to a TF engine, I'd say each exhaust pipe is like a 12 gauge shotgun, firing numerous rounds in sequence. Basically, each exhaust pulse is like a 12 gauge firing, with a lower frequency, and more air volume being expelled (hmm, possibly closer to a 50 BMG).

    Compared to a fighter jet, think a pair of TF dragsters is close or equal to an F-15 or F-18 on full afterburner. The jet has a lower frequency, but is not as concussive. But I haven't been able to measure an F-15 / F-18 at full throttle up-close. Maybe some Navy or Air Force guys could chime in (especially the guys who got to fire the engines in the hush houses, or the carrier deck crews). A B-1 Bomber with four, 30,000 pound thrust, 5-foot diameter afterburning engines beats all of them though, in terms of thunder. I watched a B-1 take off before, cold morning, full burner, from half a mile away, and it was louder than being at the track.

    I've heard that special-built competition car stereos have been measured at 180 dB, which is incredible, considering the noise and power from an 8000 horsepower TF motor. Channel all the TF's exhausts into a single pipe, and I'm sure a TF will exceed 180 dB, if the SPL meter microphone can even survive inside the pipe. The car stereo vehicles are sealed, stiffened, and the microphones are placed at the point of maximum volume, so if the same advantage is given to the engines, I bet it would be close.

    If you haven't attended an NHRA drag race event, you should go to one sometime. I highly recommend going, especially if you like raw power, noise and hot rods! You'll get addicted to it. I'd wear earplugs though, if you plan to stay all day. Definitely hit the pits, take off those earplugs, and get up close when they fire up and blip the TF motors. Hold onto your drink! :whistling:
  2. G26S239

    G26S239 NRA Patron

    Mar 17, 2008
    Excellent report, thanks for sharing your results. I have never seen Top Fuel racing but it sounds great. :thumbsup:

  3. When you watch a TF engine as filmed with a high-speed camera, you can see why they are so loud. Watch for the individual exhaust chuffs firing out of the pipes like a mortar firing out of a launch tube.

    Link to video

    I wish I could find better quality footage, but the raw power shown by the footage combined with the deafening roar is very cool.
  4. Cancer


    Jul 12, 2007
    I forgot to mention that a pair of Pro Stockers (normally aspirated V8 cars) measured 115 dB at launch, and 114 dB at the far end of the track. The Top Fuelers appear to be about twice as loud to our ears, but are actually generating about 10 times more sound power, due to the logarithmic nature of the dB scale. That sounds about right, since a TF produces significantly more horsepower than a Pro Stocker (8000 hp vs 1500 hp).
  5. Stang_Man


    Dec 3, 2006
    Great write up!

    The races are very cool to witness, they shake your insides! I couldn't imagine piloting one of these beasts!
  6. pjrocco

    pjrocco Rock

    Jul 21, 2006
    Chicago, IL
    I will be bringing my 9 year old son to his first NHRA event in the next couple weeks. Of course he'll have ear plugs in and ear muffs. Every year I go and every year I see very small children there and just can't see bringing a 1 or 2 year old to something that loud.
  7. woodasptim


    Feb 7, 2007
    NE Arkansas
    I always wondered how loud they really were. No way I would watch them without hearing protection. I always bring a pocket full of cheap foamies to give away to people who obviously need them. It's amazing how many people go unprepared and then start stuffing whatever they can find in their ears after the first run.



  8. packin23

    packin23 Welcome Wagon

    Oct 11, 2006
    Haines City, Fl.
    I love going to the Gator Nationals in Gainesville. If you can get a spot even with the tree right at the fence the amount of air these engines move is incredible. It distorts your vision so much it's like looking through very heavy gasoline vapor.
  9. Carolina Drifter

    Carolina Drifter CLM

    May 27, 2007
    NW SC
    I never go to the drags without earmuffs.
  10. okie

    okie GT Mayor

    Oct 28, 2001
    Muskogee Ok.
    Very kool study my friend :thumbsup:
  11. HoldHard


    Nov 28, 2008
    Motor City 'burbs
    I crew for a Top Fuel Harley and it only has two cylinders producing 1,000 horsepower, no where near the funny cars or dragsters. We still hand out earplugs to fans that are near our pits. The closer to the source, the louder the sound. As Cancer mentioned, you can feel the concussion waves on your body. We have to fire the bike to verify the clutch setting (it's a computer controlled, air-actuated system) and several other functions before going to the starting line. As you can see in the second picture, the fans are about 80 feet away and have their fingers plugging their ears when the bike idles.

    We video record each run so somebody (at times me) has to be directly beside the bike to tape when the back tire moves, the front tire comes up, how long it stays up and all the intricate details of the pass. If we are in the right lane, the competitor's exhaust is directly behind me. It's a bit easier if we are in the left lane, but the fumes are still at saturation level.

    I wear riding goggles to keep the unburnt fuel out of my eyes (it stings like crazy) so I can see what is being recorded, but it still gets into your nose, causing it to turn into a faucet... After the pass, there is always the 5 minutes of coughing to get the crap out of your lungs.

    And all this is after the burnout....

    Kevin Boyer, Canadian Motorcycle Drag Race Association (CMDRA) Top Fuel Champion for 2009 and will be wearing plate TF1 this year.




  12. FullClip

    FullClip NRA Benefactor CLM

    Used to go to the drag races in Epping, NH years ago, and for sure, the starting line is where the show is. Most folks have no idea of how much power can be generated (at least for a little while...:supergrin:) by an engine the same size you used to be able to get in a 'family car'.

    We always have to do a Noise Test on every new power plant, and it's kind of a joke...I always tell the new operators, don't worry about all the noise, you get used to it after a while"...:whistling:
  13. Free Radical

    Free Radical Miembro Antiguo CLM

    Sep 11, 2005
    Four Corners
    Very interesting and very well written. :thumbsup:
  14. When you think about it, it doesn't seem mechanically possible that they can go up to 330 mph in less that 5 seconds in 1/4 mile, but they do.
  15. SoonerSoftail

    SoonerSoftail Go Sooners!

    Feb 1, 2010
    We used to have a number of national drag boat racing events in OKC. They let you walk around the pits all you wanted. I was standing by a Top Fuel Flat Bottom one day and they started it up with me about five feet from the motor. If my jeans hadn't been tight they would have left me as I jumped five feet in the air. By far the loudest thing I've ever heard, and I work on an airport.
  16. BamaBud

    BamaBud NRA Life Member

    Sep 25, 2007
    Heart of Dixie
    There was a story that circulated about the Sox & Martin Hemi Cuda about 1970. It had a dual plug hemi motor, lots of horsepower.
    Anyway, it was said that one of Bill Jenkins crew (or even Bill himself) was standing next to the S&M when it was fired. The driver winged it, and the lenses in Jenkin's eyeglasses shattered from the noise!:wow:
  17. Brian Lee

    Brian Lee Drop those nuts

    Jul 28, 2008
    Up a tree.
    Glad to hear you're going to play it smart on the hearing protection. Too many people underestimate the harm they can do to their own childs hearing. A toddlers ears are especially sensitive to this kind of stuff.:wavey:
  18. community

    community Member

    Jan 14, 2009
    SE Michigan
    thanks for sharing. awesome machines.
  19. 686Owner

    686Owner NRA Life Member

    Mar 10, 2007
    I think they are a little less than 180db in the car stereo world. Each 3db increase takes a doubling of power.

    My stereo topped out at 130db or so. It was pretty loud and I could not stand to turn it all the way up unless I wanted a headache.
  20. boozer


    Jul 24, 2007
    Hilltop, USA
    I remember a video of a crewmember standing too close to the "zoomies" (man I'm old) and they blew his pants off. Ripped them to shreds.

    TF racers are awesome, you can't focus as they go by. Doesn't last long though.