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spl corection for non radio shack meters


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#1 of 7 rob hoinsky

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Posted December 09 2004 - 09:44 AM

i bought an American Recorder spl-8800 a while back thinking it was more accurate than the radio shack model that everyone uses, but i can't find any corrections for it. does anyone know where i might find them?

thanx

#2 of 7 Edward J M

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Posted December 09 2004 - 10:45 AM

Is the meter c-weighted?
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#3 of 7 rob hoinsky

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Posted December 09 2004 - 01:02 PM

it can be a weighted or c weighted

although i'm not sure where you're going with this...

#4 of 7 Edward J M

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Posted December 09 2004 - 11:57 PM

Set the meter to C-weighted for FR sweeps or peak SPL monitoring.

The A-weighted scale rolls off the response starting up around 500 Hz and is not useful for HT applications, only industrial noise monitoring.

In the absence of specific correction factors for this particular meter, use the following CFs. They are the theoretical CFs for the C-weighted filter in your meter and will be quite sufficient for informal FR sweeps to identify and correct response anomalies, etc.

Thank DougBW (Trilogy over at HT-SPOT) for these; he gave them to me about two years ago for my B&K SPL meter, which is also C-weighted.

Regards,

Ed

FrequencyC-Weight
10-14.33259693
10.59463094-13.52968703
11.22462048-12.74595335
11.89207115-11.98268094
12.5992105-11.24113838
13.34839854-10.52255777
14.14213562-9.828113197
14.98307077-9.158898305
15.87401052-8.515903684
16.81792831-7.899994991
17.81797436-7.311892737
18.87748625-6.752154684
20-6.221161728
21.18926189-5.719108023
22.44924097-5.24599587
23.7841423-4.801635653
25.198421-4.38565084
26.69679708-3.997487754
28.28427125-3.6364296
29.96614154-3.30161399
31.74802104-2.992053117
33.63585661-2.706655603
35.63594873-2.444249093
37.75497251-2.203602722
40-1.983448665
42.37852377-1.782502185
44.89848193-1.599479687
47.5682846-1.43311451
50.396842-1.282170279
53.39359417-1.145451828
56.56854249-1.021813749
59.93228308-0.910166743
63.49604208-0.809481987
67.27171322-0.718793751
71.27189745-0.63720053
75.50994501-0.563864932
80-0.498012574
84.75704755-0.438930194
89.79696386-0.385963182
95.1365692-0.338512687
100.793684-0.296032457
106.7871883-0.258025523
113.137085-0.224040813
119.8645662-0.193669799
126.9920842-0.1665432
134.5434264-0.142327811
142.5437949-0.12072348
151.01989-0.101460247
160-0.08429567
Ed Mullen
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#5 of 7 rob hoinsky

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Posted December 10 2004 - 03:09 AM

thank you and thank you doug

a little confusion, are those all subtraction?

#6 of 7 Craig Morris

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Posted December 10 2004 - 03:32 AM

This is from my Revel B15 LFO Software .ini file. It includes the corrections for Radio Shack Analog and Digital... and also lists the following for "other".


[Other "C-Weighted" Sound Level Meter]
20=6.2
21=5.7
22=5.3
24=4.9
25=4.4
27=4.0
28=3.7
30=3.3
32=3.0
34=2.8
36=2.5
38=2.2
40=2.0
43=1.8
45=1.6
48=1.4
50=1.3
53=1.2
56=1.0
60=0.9
63=0.8
67=0.7
71=0.6
75=0.6
80=0.5
95=0.4
90=0.4
95=0.3
100=0.3

#7 of 7 Edward J M

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Posted December 10 2004 - 06:42 AM

Quote:
a little confusion, are those all subtraction?


Yes, that's how far low (hence the negative) the meter will read at a given frequency.

So you ADD that amount to the meter reading to obtain the actual SPL.

So at 20 cycles, a c-weighted SPL meter will be reading about 6.2 dB low. So if the meter reads 80 dB, the actual sound pressure is 86 dB. And so forth for all the other frequencies listed above.

Regards,

Ed



Regards,

Ed
Ed Mullen
Director - Technology and Customer Relations

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"What we do in life, echoes in eternity."