Can I subtract a measurement from another ( difference ) ?

[redmountain]

as the title says...
?
Thanks

Klaus

 

[linuxonly]

Hi,

It's readily available in the Beta version: Trace Arithmetics -> A-B

 

[John Mulcahy]

In 5.31 you can find trace arithmetic from the All SPL graph.

 

[redmountain]

Yes
but
A-B doesn't reflect the actual difference in dB
i.e.100dB@100Hz - 90dB@100Hz I would like to see as
-10dB@100Hz
Hope to be clear...

Thanks

Klaus

 

[John Mulcahy]

Subtraction of dB values corresponds to trace division.

 

[redmountain]

This I don't understand...

 

[John Mulcahy]

dB traces are produced from the log of the underlying data, for magnitude responses the trace values are 20*log10(data values). log(A/B) = log(A) - log(B), i.e. division of the underlying data sets corresponds to subtraction of the logs of their values.

 

[redmountain]

sorry, that is to much for me
Thank you anyway !
It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line
Best regards

Klaus

 

[linuxonly]

sorry, that is to much for me
Thank you anyway !
It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line
Best regards

Klaus

Hi,

Like John told you in https://www.avnirvana.com/threads/c...ent-from-another-difference.14245/post-107978 , use trace arithmetics -> A/B
Don't tick 'max gain'

 

[redmountain]

Thank you
I misinterpreted A-B
A/B means A divided by B here
A-B means A subtracted by B

Sorry...

 

[John Mulcahy]

It would be great for me to have an arithmetic difference shown between 2 measurements, defaukting on a flat 'zero +/- line

Use this:

 

[redmountain]

Yes
linuxonly told earlier
Thank you
and all the best

Klaus