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- Nov 25, 2003
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Now before I go any further I am going to say that this post is for information & for those of you who have or have access to a Radio shack dB meter to try this for yourselves only. It is not up for debate, dispute, basis for argueing the rule or anything of that nature so please don't even think of posting anything like that here. Anyone who does so I will request the powers that be to have said post removed as we need to stop this insane bickering & move forward, this is an attempt to do just that. With that being said on to the good stuff.
Follow along on some really good info from our dB calibration connection at an area Air Force base & what we need to do that can have a significant impact on our attempts to measure dB's with the Radio Shack meter. This individual, because of the nature of what he does, needs to remain nameless but he has been a sound expert with the Air Force for over 17 years-
There are 2 different types of microphone pick ups (mics) used in dB meters, omnidirectional & unidirectional and the Radio Shack is omnidirectional from what this guy told us. We now have, on loan from the Bayer Corp., a $2,000 dB meter that he just completed calibration testing (it was basically on the money) that is fully ANSI S1.4-1983 compliant which is the standard recommended for outdoor sound measuring of automotive or internal combustion engines, pretty much things like race tracks & arenas which happens to be similar to what we are trying to do. This meter has a unidirectional mic in it that is distinguished by it's longer pickup inlet. The unidirectional is more target specific or one as in "uni" and less hampered by reflective noise. The Radio Shack meter uses an omnidirectional (multidirectional) pickup because it's primary selling point is for home stereo use where you do want to take into account the reflected sounds. For those that remember them think back to when the first Bose 901 home stereo speakers came out, they were totally based on reflected sound. Anyway regardless of that the R/S unit still is a fairly good meter & the +/- 2dB in the specs is really rather excessive based on what our guy has told us. The calibrated R/S meter & the ANSI meter in some quick tests were within about a tenth of each other in the 80-100dB target range (and just a note the R/S meter when it got calibrated was barely off in the 80-100dB range). The thing that is killing the R/S meter readings is the reflected sound. Now here's the good part, all one needs to do the make the R/S unit much more of a unidirectional type pick up is to push roughly a 2" piece of the 90 size (approx. 7/8" i.d.) silicone pipe coupler up over the inlet ( you want about an 1 1/2" remaining in front if inlet) so the mic or pickup now has to focus through the tube. (the 1 1/2" distance is about where the mic is placed in the inlet tube of the unidirectional meters, the R/S mic is right at the front) Based on the info from our Air Force buddy this should have a major impact on the R/S meter being much more directional & better suited for what we are trying to do. While I do not own a Radio Shack meter this has already been tried for me by someone who does own one & the difference was quite distinct. He was not however able to do this with boats because of the cold weather in his area, he had to experiment with outdoor yard equipment to generate a sound test bed. I'm hoping some of you who can run this weekend and has or has access to one of these R/S meters to add on the silicone tube & give this a try and see for yourselves. This could be a very big step, but certainly not the only one, in getting things better for this season. Good testing to all. B)
Follow along on some really good info from our dB calibration connection at an area Air Force base & what we need to do that can have a significant impact on our attempts to measure dB's with the Radio Shack meter. This individual, because of the nature of what he does, needs to remain nameless but he has been a sound expert with the Air Force for over 17 years-
There are 2 different types of microphone pick ups (mics) used in dB meters, omnidirectional & unidirectional and the Radio Shack is omnidirectional from what this guy told us. We now have, on loan from the Bayer Corp., a $2,000 dB meter that he just completed calibration testing (it was basically on the money) that is fully ANSI S1.4-1983 compliant which is the standard recommended for outdoor sound measuring of automotive or internal combustion engines, pretty much things like race tracks & arenas which happens to be similar to what we are trying to do. This meter has a unidirectional mic in it that is distinguished by it's longer pickup inlet. The unidirectional is more target specific or one as in "uni" and less hampered by reflective noise. The Radio Shack meter uses an omnidirectional (multidirectional) pickup because it's primary selling point is for home stereo use where you do want to take into account the reflected sounds. For those that remember them think back to when the first Bose 901 home stereo speakers came out, they were totally based on reflected sound. Anyway regardless of that the R/S unit still is a fairly good meter & the +/- 2dB in the specs is really rather excessive based on what our guy has told us. The calibrated R/S meter & the ANSI meter in some quick tests were within about a tenth of each other in the 80-100dB target range (and just a note the R/S meter when it got calibrated was barely off in the 80-100dB range). The thing that is killing the R/S meter readings is the reflected sound. Now here's the good part, all one needs to do the make the R/S unit much more of a unidirectional type pick up is to push roughly a 2" piece of the 90 size (approx. 7/8" i.d.) silicone pipe coupler up over the inlet ( you want about an 1 1/2" remaining in front if inlet) so the mic or pickup now has to focus through the tube. (the 1 1/2" distance is about where the mic is placed in the inlet tube of the unidirectional meters, the R/S mic is right at the front) Based on the info from our Air Force buddy this should have a major impact on the R/S meter being much more directional & better suited for what we are trying to do. While I do not own a Radio Shack meter this has already been tried for me by someone who does own one & the difference was quite distinct. He was not however able to do this with boats because of the cold weather in his area, he had to experiment with outdoor yard equipment to generate a sound test bed. I'm hoping some of you who can run this weekend and has or has access to one of these R/S meters to add on the silicone tube & give this a try and see for yourselves. This could be a very big step, but certainly not the only one, in getting things better for this season. Good testing to all. B)
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