dbC from sweep measurement?

[thothsong]

Is there a way to obtain a dBC weighted value from an existing sweep measurement?

 

[John Mulcahy]

You could multiply the response by a C weighting curve if that's what you are looking for, A and C weighting curves attached.

 

[thothsong]

Thanks. That gives me a weighted curve, but not a number. What I think I'm looking for is, if I had the RTA configured for Forever averaging, and the average looked like the sweep measurement, what would the RTA report as the dBC. Does that make sense?

 

[John Mulcahy]

No, that doesn't really make sense. The sweep provides a transfer function measurement that is presented offset to an equivalent SPL for any particular moment of the sweep, but it doesn't represent an overall SPL measurement and it wouldn't be meaningful to try and assign an SPL figure to it. If you were to export the data and calculate one it would come out very, very high. As an example, here is what the RTA looks like for a 75 dB (approx) periodic noise input using the CTA-2034 shaping, with a 64 k FFT. Note the levels, the graph is shown without the "Adjust RTA levels" option which artificially shifts the plot to provide easier comparison with sweep measurements.

 

[thothsong]

OK, thanks for the explanation, I think I get it. To then ask the question I should have asked in the first place: If I only have sweep measurements for two speakers, is there any way to derive a comparison between them that would be similar to playing some type of pink noise and taking a dBC measurement?

 

[John Mulcahy]

If you are interested in comparing the response levels over some frequency span you could use the graph metrics for that, assuming they are comparable (e.g. measured at the same sweep level and distance in the same environment).

 

[thothsong]

OK, thanks.