Measuring boat engine noise

Discussion in 'Diesel Engines' started by burke, Jul 21, 2014.

  1. burke
    Joined: May 2014
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    burke Junior Member

    Does anyone have experience measuring boat noise prior to improving it? I have a 26’ Downeast type boat with hard top pilot house and a 150HP Volvo turbo diesel under an engine box. I have heard some affordable Smartphone apps can measure the sound level and frequency. Can you recommend one?

    Where is it useful to make readings? At cruising speed I assume.

    Thanks
     
  2. CloudDiver
    Joined: Jun 2014
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    CloudDiver Senior Member

    I haven't done this with boats, but I have done it extensivley with motorcycles when EPA and CARB came down on hard on after-market exhaust and custom built bikes. I used an electronic decible meter, about $25. I got mine from Fry's Electronics, but I think they also have them on the Radio Shack website and Amazon. The key feature they have is that will hold at the highest decible reading during a session, or you can switch to where it constantly reads just that moments level. According to new regulations at the time (2007), exhaust noise was recorded from 15 ft away behind the motorcycle. This crap comes up even on race-tracks where they will not permit you to ride a bike with a non-factory exhaust. Who the F rides a 'stock' bike on Laguna Seca? thats why this guy has never made the 8 hour trip to Monterey, CA to ride that race track.... but I digress.

    I haven't tried any smartphone aps, I would wonder about the sensitivity and calibration. On the same token, even if not perfectly calibrated, I think it will work out fine for your intended comparison. Just look for an Ap that specifies if it Holds at the highest decible reading each time you take a reading.

    I'd reccomend recording the noise at start-up, throttle to leves of idle, 1/3 forward, 1/2 forward, Full, and reverse. You can take levels from the Helm, on deck, in the cabin... wherever you feel appropriate but repeatable. I'd recommend having a few friends with the same phone Ap at each of these locations so you don't have to repeat the tests a dozen times. Then do your engine improvements and repaeat the same sequence of readings at the same locations, hopefully under the same sea-state and general weather conditons.
     
  3. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    They sell for about $27 at Radio Shack and they have A and B weights.
     
  4. Stumble
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    Stumble Senior Member

  5. Moggy
    Joined: Feb 2011
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    Moggy Senior Member

    For Android...

    https://play.google.com/store/apps/details?id=kr.sira.sound&hl=en

     
  6. burke
    Joined: May 2014
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    burke Junior Member

    Thanks. What do you mean "use with an auxiliary tool"?
     
  7. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    boats are complicated as you also have to measure structure born noise, and be able to separate that from direct radiated noise.
     
  8. Stumble
    Joined: Oct 2008
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    Stumble Senior Member

    Burke,

    Its just saying that since phones aren't designed for scientific measuring of noise they can't be relied on in sound engineering or for regulatory approval.
     
  9. Moggy
    Joined: Feb 2011
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    Moggy Senior Member

    I think he is referring to professional use, meaning that you need a dedicated meter to do a proper job.
     
  10. Richard Woods
    Joined: Jun 2006
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    Richard Woods Woods Designs

    I tried a free iphone dB ap when I wanted to see how loud my 20hp Tohatsu outboards were on my Skoota 28 powercat. Nothing to lose....

    I was less interested in the ACTUAL noise level, more in the relative noise when compared to other boats and machines. So I tried it on the boat and then in our car.

    Then I got the official dB readings for the car and compared the results.

    At the helm the engines at cruising speed were 2dB higher than in the car at 75mph

    That was good enough for me. I got my moneys worth out of the ap

    Richard Woods of Woods Designs

    ww.sailingcatamarans.com
     
  11. d1970
    Joined: Jun 2012
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    d1970 Junior Member

    Try Sound Meter or Noise Meter on android.
    Compare between the two. Try to take a reading from a known source,
    like a pump or such,before so you know by how much it's off. Go at it in the engine room, cabin,guest room,etc.
     

  12. AndySGray
    Joined: Jun 2014
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    AndySGray Senior Member

    Not scientifically correct to use Decibels for Relative noise measurement.

    The correct unit is the mBSMIL, micro BSMIL - more commonly called a micro Besimil - which not only deals with the volume of the noise but also how well it is tolerated by the listener.

    This is an SI (International System of Units) unit, its derivation being one thousandth of the sound pressure wave (in pascals / Newtons per square Meter) generated by a British Standards Institute / American National Standards Institute Standardised Mother in Law.:D

    Anything over 75 on that scale requires hearing protection and consumption of Alcohol:!:

    :p
     
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