poctave() return value for acoustics analysis
Hi all,
I need some assistance understanding the "units" of the data that is returned when calling the MATLAB function [p,cf] = poctave();
I am analysing an audio signal that has been recorded with a microphone. The data is imported into the MATLAB workspace and converted to a calibrated pressure value with units of Pascals (Pa). So the units of the data that I pass to poctave() are Pascals (Pa). The following code snippet shows how I’m using poctave().
flims = [20 Fs/2]; % set the frequency limits of my analysis
bpo = 3; % Third-Octave analysis required
opts = {‘FrequencyLimits’,flims,’BandsPerOctave’,bpo}; % prepare these options for passing to poctave()
% apply the 3rd-Octave filter-bank to my data
[p, cf] = poctave(pressureData,Fs,opts{:});
(Where "pressureData" is my audio data to be filtered, and "Fs" is the sampling frequency of the data.)
My first question is:
1) What are the units of the octave spectrum data returned unto variable ‘p’?
I need to know this for my conversion of the data into a dB value using 10*log10(p/pref).
I understand that if I use poctave() as follows:
poctave(pressureData,Fs,opts{:})
then by default it assigns "pref" a value of 1 and the results are as in the following image:
Without units though, the result seems meaningless…
My second question is:
2) what is pref in the previous equation to ensure correct dB values that correlate with a sound pressure level? do I use:
pref = 0.00002; % 20 micro Pascals reference sound pressure level
or:
pref = 0.00002^2; % 20 micro Pascals (squared); i.e. is p returned from poctave() a pressure squared value or a power value??
I want to create a resulting 3rd-Octave spectrum whos dB values match those as though it was being displayed on a Sound Level Meter. I will then correlate these values with those on our Sound Level Meter to validate the data to be processed within MATLAB.
Thanks so much for any assistance you can offer!!Hi all,
I need some assistance understanding the "units" of the data that is returned when calling the MATLAB function [p,cf] = poctave();
I am analysing an audio signal that has been recorded with a microphone. The data is imported into the MATLAB workspace and converted to a calibrated pressure value with units of Pascals (Pa). So the units of the data that I pass to poctave() are Pascals (Pa). The following code snippet shows how I’m using poctave().
flims = [20 Fs/2]; % set the frequency limits of my analysis
bpo = 3; % Third-Octave analysis required
opts = {‘FrequencyLimits’,flims,’BandsPerOctave’,bpo}; % prepare these options for passing to poctave()
% apply the 3rd-Octave filter-bank to my data
[p, cf] = poctave(pressureData,Fs,opts{:});
(Where "pressureData" is my audio data to be filtered, and "Fs" is the sampling frequency of the data.)
My first question is:
1) What are the units of the octave spectrum data returned unto variable ‘p’?
I need to know this for my conversion of the data into a dB value using 10*log10(p/pref).
I understand that if I use poctave() as follows:
poctave(pressureData,Fs,opts{:})
then by default it assigns "pref" a value of 1 and the results are as in the following image:
Without units though, the result seems meaningless…
My second question is:
2) what is pref in the previous equation to ensure correct dB values that correlate with a sound pressure level? do I use:
pref = 0.00002; % 20 micro Pascals reference sound pressure level
or:
pref = 0.00002^2; % 20 micro Pascals (squared); i.e. is p returned from poctave() a pressure squared value or a power value??
I want to create a resulting 3rd-Octave spectrum whos dB values match those as though it was being displayed on a Sound Level Meter. I will then correlate these values with those on our Sound Level Meter to validate the data to be processed within MATLAB.
Thanks so much for any assistance you can offer!! Hi all,
I need some assistance understanding the "units" of the data that is returned when calling the MATLAB function [p,cf] = poctave();
I am analysing an audio signal that has been recorded with a microphone. The data is imported into the MATLAB workspace and converted to a calibrated pressure value with units of Pascals (Pa). So the units of the data that I pass to poctave() are Pascals (Pa). The following code snippet shows how I’m using poctave().
flims = [20 Fs/2]; % set the frequency limits of my analysis
bpo = 3; % Third-Octave analysis required
opts = {‘FrequencyLimits’,flims,’BandsPerOctave’,bpo}; % prepare these options for passing to poctave()
% apply the 3rd-Octave filter-bank to my data
[p, cf] = poctave(pressureData,Fs,opts{:});
(Where "pressureData" is my audio data to be filtered, and "Fs" is the sampling frequency of the data.)
My first question is:
1) What are the units of the octave spectrum data returned unto variable ‘p’?
I need to know this for my conversion of the data into a dB value using 10*log10(p/pref).
I understand that if I use poctave() as follows:
poctave(pressureData,Fs,opts{:})
then by default it assigns "pref" a value of 1 and the results are as in the following image:
Without units though, the result seems meaningless…
My second question is:
2) what is pref in the previous equation to ensure correct dB values that correlate with a sound pressure level? do I use:
pref = 0.00002; % 20 micro Pascals reference sound pressure level
or:
pref = 0.00002^2; % 20 micro Pascals (squared); i.e. is p returned from poctave() a pressure squared value or a power value??
I want to create a resulting 3rd-Octave spectrum whos dB values match those as though it was being displayed on a Sound Level Meter. I will then correlate these values with those on our Sound Level Meter to validate the data to be processed within MATLAB.
Thanks so much for any assistance you can offer!! poctave, audio signal processing, spectrum, acoustics MATLAB Answers — New Questions