Sound Pressure level returning -inf

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Hello Community;
when I use the function [Lt,Leq,Lpeak,Lmax] = SPL(recording_vector) it returns vectors containing (partially or completely) -inf values. Surprisingly when I re-Run the same line I get usual numeric values. how is this possible? how to avoid it?
Thanks
  2 Comments
Farid
Farid on 3 Sep 2022
Thanks a Lot Chunru, I am attaching the file to this comment.
calib=importdata('calib.mat')
IRS=importdata('IRS.mat')
spl = splMeter("CalibrationFactor",calib, ...
"FrequencyWeighting","Z-weighting", ...
"TimeWeighting","Fast", ...
"TimeInterval",0.125, ...
"SampleRate",FS,...
"Bandwidth","1 octave");
[Lt,Leq,Lpeak,Lmax] = spl(IRS)

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Accepted Answer

Jimmy Lapierre
Jimmy Lapierre on 7 Sep 2022
Leq, Lpeak and Lmax are only computed every TimeInterval, so they correspond to the SPL of zero for the first 0.125 seconds. And as chunru said, that corresponds to -Inf. When you call spl a second time, you are already pass the first 0.125 seconds of pure silence.
To avoid it, either discard the fist 0.125 seconds, or set a minimum value you prefer.
For example set any value below -100 dB (including -Inf) to -100:
Leq(Leq<-100)=-100;

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