Sound Level meter requirements

[tony at radiosouthrc.com]

Del:
The problem with all meters I know of is that they all change!  I was the first one in the USA to work with the FAI in establishing how a db check would actually be done in the field.  I did the first ones at the 1983 US Team Selections in Rough River, KY right before the 1983 World Champs.  As I was the assistant CD for the WC, AMA wanted me to gather the data and learn how the system the FAI had designed would really work in the field.  We found that even expensive db meters developed drift.

The expensive versions used by AMA have to be adjusted about every 4 hours, as they can drift 1/2 to 1 1/2 db in that period of time due to temperature changes.  That is the problem with any meter.  Unless you have a calibrator to adjust the meter, it is really pretty worthless in getting an accurate measurement.  As long as + or - 5 db is OK, you don't need to worry.  However, if you are trying to meet any model noise requirement out there, your really spinning your wheels.  

Tony Stillman
Radio South
3702 N. Pace Blvd.
Pensacola, FL 32505
1-800-962-7802
www.radiosouthrc.com
  ----- Original Message ----- 
  From: Del K. Rykert 
  To: discussion at nsrca.org 
  Sent: Wednesday, February 16, 2005 12:01 PM
  Subject: Re: Sound Level meter requirements


  I had a friend calibrate  my R.S. meter. it was off 2dB. Not inferring that it is best meter. Just they can be adjusted. How well it hold the adjustment I have no  clue.

      Del

    ----- Original Message ----- 
    From: Bob Richards 
    To: discussion at nsrca.org 
    Sent: Wednesday, February 16, 2005 8:45 AM
    Subject: Re: Sound Level meter requirements


    Good point.

    For my use (making comparisons) the RS meter is fine. The club I formerly belonged to also used them for enforcing a club-imposed noise limit.

    However, if it comes down to enforcing a local noise ordinance, a calibrated meter traceable to NIST would probably be required. I'm not sure, but I don't see why you would not be able to have a RS meter calibrated, although I am sure the measurement uncertainty would not be very good. I'm sure the calibration would probably cost more than the RS meter.

    What are/were the circumstances of "needed in a court of law" are you referring to?

    Bob R.

    Lance Van Nostrand <patterndude at comcast.net> wrote:
      Earl/John,
      Our club bought a RS meter and I remember Gray taking it to a contest where 
      either Earl or Mike Harrison had their Extech. The RS meter was 2 db off 
      and had no calibration. We then bought the Extech and found that the 
      calibration ability and the specs are needed in a court of law.
      --Lance

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