Plotting sound pressure level

Hello,

I am working on intensity probe to develop sound meter level. I did the fft and calculated sound pressure levels as well as sound power level using sound pressure level Lp=20log10(P/Pref) and sound power level Lw= Lp+5.344. The size of columns Lp and Lw is 1024x1 and size of frequency column in fft calculations is 1x513. How can I overcome this problem?

Sample rate is 16384

blocksize is 1024

frequency resolution is 50Hz

Signal is sine wave with frequency amplitude 6400

Thank you.

for i = 1 : numel(RealPa)
  Lp(i, 1) = log10(RealPa(i))+ log10(100000)-log10(2);  %Sound Pressure Level Calculation
end

for i=1:numel(Lp)
Lw(i,1)=Lp(i)+5.344;   %Sound Power Level Calculation
end

%Beow is code for FFT
[d,s]=xlsread('CHANNEL1.xlsx');
t=d(:,1);
p=d(:,2);
L=length(t);
Ts=mean(diff(t));
Fs=1/Ts;
Fn=Fs/2;
pc=p-mean(p);
FTv=fft(pc)/L;
Fv=linspace(0,1,fix(L/2)+1)*Fn;
Iv=1:length(Fv);
figure(1)
plot(Fv,abs(FTv(Iv))*2)
grid
xlabel('Frequency in Hz')
ylabel('Amplitude in Pa')

Answer 1

[Soham Chakraborty]

Hi,

In order to get the sound pressure level of an audio signal, you can use the splMeter system object. You can refer to the following link for more information about it: https://www.mathworks.com/help/audio/ref/splmeter-system-object.html

You can declare the object as follows:

SPL = splMeter('SampleRate', frequency_value);

Then you can get the sound pressure level data that corresponds to that specific frequency value as follows:

[y, Fs] = audioread(name_of_file); >> [Lt,Leq,Lpeak,Lmax] = SPL(y);

You would have to repeat these steps for each one of the frequency value in the y array and form a matrix with all the sound pressure level data that corresponds to the frequency data.

You can find the time array that corresponds to the y array (the signal values) as follows:

time_in_sec = (1:size(y,1))/Fs;

[Alok Bendale]

Thank you for your response and also extremely sorry for replying so late, but I have data in terms of pressure not as an audio file. The attached file is one of the samples I have taken with two microphones.