How to obtain ΔSPL vs frequency graph?

Hello guys,

I'm trying to do a noise analysis on my aerofoil experiment. So far I have able to obtain the sound pressure level (SPL in dB) vs frequency graph. However, I'd like to create graphs with ΔSPL vs frequency, comparing each case with the baseline. I am not sure how to subtract two graphs.

I am not quite familiar with Matlab, I would so appreciate your help.

Kind regards,

Xyki

[Mathieu NOE]

hello

if you have created the SPL of the baseline (and store it in a variable, let's call it SPL_baseline) , why couldn't you make the delat computation for the next cases ?

dSPL_new = SPL_new - SPL_baseline; % for each "new" case

[Xyki]

Hello Mathieu,

I have created a graph for all cases including the baseline. So I have extracted the x and y data out and do a subtraction. Is this what you mean?

Thanks for you help.

Xyki

[Mathieu NOE]

hello Xyki

yes , this should be ok

maybe if you show a picture of the data graph before and after doing the delta , I could confirm my belief

[Xyki]

Hello Mathieu,

Please see the attached files. The deltaSPL graph looks alright to me with the peak reduction corresponding to the largest difference in the SPL graph.

Thanks for your help.

Kind regards,

Xyki

[Mathieu NOE]

hello Xyki

yes , this is ok !

good job

[Xyki]

Hello Mathieu,

Thank you for your help.

Xyki

[Mathieu NOE]

hello Xyki

my pleasure !