find power of signal

Hi, how do i find total power of signal from a wav file and display it on axes ? I currently only have this.

[myRecording,fs] = audioread('filename.wav',[1,2*8000]); %fs = sample rate

Nsamps = length(myRecording);

t = (1/fs)*(1:Nsamps); %Prepare time data for plot

%Do Fourier Transform

y_fft = abs(fft(myRecording)); %Retain Magnitude

y_fft = y_fft(1:Nsamps/2); %Discard Half of Points

f = fs*(0:Nsamps/2-1)/Nsamps; %Prepare freq data for plot

%Plot Sound File in Time Domain

plot(handles.normalLies,t, myRecording)

xlabel(handles.normalLies,'Time (s)')

ylabel(handles.normalLies,'Amplitude')

%Plot Sound File in Frequency Domain

plot(handles.fttLies,f, y_fft)

xlim(handles.fttLies,[0 20])

xlabel(handles.fttLies,'Frequency (Hz)')

ylabel(handles.fttLies,'Amplitude')

Answer 1

[Shoaibur Rahman]

In time domain: for discrete signal x(n)

Instantaneous power = x(n)^2

Average power = (1/N) * sum(x(n).^2)

N = data length or period

Answer 2

[Image Analyst]

The total power would be a single number - a scalar. Do you mean power as a function of frequency, like the spectrum like you'd get from pwelch(), or fft()? From the help: "pxx = pwelch(x) returns the power spectral density (PSD) estimate, pxx, of the input signal, x, found using Welch's overlapped segment averaging estimator. " pwelch() is in the Signal Processing Toolbox. There is a webinar on spectral analysis that hopefully you can find on the Mathworks web site that goes over it and the fft in detail.