iiyama
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| posted on 16/4/09 at 12:09 PM |
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Noise meters
Anyone know anything about them?? Basically I need to know if ± 3.5dB @1KHz, 94dB is accurate enough to check the car? Failed noise at SVA and want to
be certain of a pass when I take it back! Other options on the bay include meters with an accuracy of +/- 2dB @ 114dB but this is an analogue meter
where as the former is digital. If the latter had a hold feature it wouldnt be too bad I guess, but it hasnt. The former is easier to read and has
hold.
Hit me with your knowledge geeza's! 
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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dan__wright
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| posted on 16/4/09 at 12:14 PM |
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i got a digital one on the bay with an acuracy much better than that for about £40 it was +- 1 i think
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iiyama
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| posted on 16/4/09 at 12:16 PM |
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Both of these are half that dude, hence the accuracy.......or lack of it!!!
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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v8kid
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| posted on 16/4/09 at 12:33 PM |
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Bought a digital one from Maplin about £20 ish mebbe less and it seems OK.
I compared it to a professional one at the track and in the round it was within 3dB.
I say in the round because it was incredibly difficult to get a consistent reading due to reflections, passing traffic, standing in a diffeent
position etc.
At the end of the day the absolute accuracy is not the issue it is the reduction in output you want to see.
Take 5 or 6 readings before any mods and average them,, then do the same after the mods and see the difference.
Remember to use the right weighting and scale range. These things default to the low range after a few mo and the results are rubbish.
By the way 3dB is 50% power so they are really woefully inaccurate!!
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BenB
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| posted on 16/4/09 at 12:35 PM |
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The problem always with noise meters is calibration (or lack of).
When uncalibrated are useful for relative measurements (e.g. measure with a standard exhaust, change can, re-measure, see if quieter or louder) but
just because your noise meter says you're running at 95dB doesn't mean you'll pass SVA when you're measured with a properly
calibrated one....
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iiyama
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| posted on 16/4/09 at 12:39 PM |
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Ive already modifiyed the SVA/MOT can. Guess I could pull out the mods and take a before and after reading. If I fail on noise its gonna cost me £40
anyway for another retest so figured I could spend up to £40 on a meter and make a decent attempt at passing. Gotta drop the noise by 2.5Dba
[Edited on 16/4/09 by iiyama]
If its broke, fix it. If it aint broke, take it apart and find out how it works!
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matt_claydon
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| posted on 16/4/09 at 01:04 PM |
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As Ben says, unless properly calibrated they are only useful for comparisons or very rough measurements.
Also, the site used makes a big difference (floor surface, nearby structures, etc) so a reading you make may not bear much relation to what is taken
at the SVA.
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