Measuring boat engine noise

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

 

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.

 

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

 

The https://itunes.apple.com/us/app/splnfft-noise-meter/id355396114?mt=8 app got very good reviews in scientific studies, and was proven acurate within +\- 2db which is the accuracy standard required by OSHA for sound testing. It is not certified by OSHA, but NIOSH was pretty impressed.

 

For Android...

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

 

Thanks. What do you mean "use with an auxiliary tool"?

 

boats are complicated as you also have to measure structure born noise, and be able to separate that from direct radiated noise.

 

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.

 

I think he is referring to professional use, meaning that you need a dedicated meter to do a proper job.

 

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

 

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.

 

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.

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