Jagthack

My Feedback: (11)

Hey guys,
I'm looking for a good db meter to check my planes for AMA standards. I found a ton on Ebay but I'm not sure what I'm buying. Is there any type or specific meter I'm looking for? I don't need the best most expensive meter out there just something that works. Any recommendations?
Thanks,
Jag

TimJ

Just a though: If you have an Ipad or Iphone you can download an app for it.

Silent-AV8R

The Radio Shack meter seems to be the one I've seen most used. The thing is, to get a true high quality meter costs way more than what most people will spend. For instance, the one I use to document compliance with various City sound ordinances costs in excess of $15,000 and it is properly calibrated before each use. I am also curious which "AMA standards" you are talking about?

beepee

As Silent says, an accurate meter is very expensive. Obtaining relative readings (how one plane compares to another) can be done with cheaper equipment. Prepare a standard measurement practice for your location. Meter position, aircraft position, over grass or pavement, that sort of thing. Gather readings and see where they fall. I think you will find that there will be a consistency of results. The loud ones will stand out. With cheaper equipment you will not have a certifiable result, but you will know when you have an aircraft with a stand-out high noise level.

Now for the elephant in the room: what do you do about it?

Have fun!

Bedford

cj_rumley

The RS meter actually compares well in accuracy with much more expensive meters.   Not really surprising, as the dB scale is logarithmic so any error in measurement is compressed, e.g., a doubling of physical sound pressure level on a linear scale produces only a 6 dB increase in the measured level on the dB scale.   What drives the cost of the meter Silent uses is the capability to log measurement data and integrate it over time.    That capability is essential for the use Silent mentioned.   Environmental standards as specified in ordinances (almost always, except in rare instances like Riverside Co, CA where the drafters didn't know what they were doing)  specify  'equivalent' sound levels, an average level over a given integration period, usually 1 hour.  This takes into consideration the fact that persistence of a sound is as important  as level is to correlation with the level of disturbance it causes.   A meter like the one from RS can only measure instantaneous level, and while it is useful in a controlled setting while manually recording the duty cycle(s) account for the time factor, it isn't practical for field measurements such as conducted to demonstrate ordinance compliance. 
FWIW, our club uses the RS meters to qualify individual MA routinely, and a rented instrument such as Silent uses to conduct periodic sound surveys at the property line (a couple of years apart) to assess/demonstrate compliance with the standards of the locality.