Plotting the maximum amplitude of p as a function of range.

Hey guys, I am not sure how plot of the maximum amplitude of p as a function of range.

Could I find the maximum amplitude of p by using peak = max(signal) or do i need another function in matlab?

I am also unsure how I should write it with the loops, since it is my first time working with loops.

Thanks in advance

P1=1; % The sound pressure in Pa at 1 m range
f = 1e3; % The frequency, Hz
w = 2*pi*f; % Angular frequency, radHz 
c = 340; % Sound speed, m/s
lambda = c/f; % Wavelength, m
k = 2*pi/lambda; % Wave number, m-1
r = 0.1:0.01:10; % range vector, interspaced by 1 cm
fs = 1e5;
t = [0 : 1/fs : 10/f ]; %time scale, running over ten periods
for i=1:length(t)
    p(i,:) = (P1./r).*sin(w*t(i)-k*r); 
end

for i=1:length(t)
    plot(r,p(i,:));
    title([ num2str(t(i)) ' s'])
    xlabel('m');
    ylabel('Pa')
    axis([0 max(r) -10 10])
    pause(0.1)
end

for i = 1: length(r)
    plot(t',p(:,i));    
    title([num2str(r(i)) ' m'])
    xlabel('s');
    ylabel('Pa')
    axis([0 max(t) P1*[-10 10] ])
    pause;
end

Answer 1

[Star Strider]

It seems that the first figure does exactly that.

I would also put each loop in a separate figure:

figure
for 
...
end

figure
for
 ...
end

If you simply want to plot the magnitudes of the peaks, the findpeaks (link) function will isolate their amplitudes and distances for you. Use it with the columns of ‘p’. I leave it to you to experiment, since I’m not certain what you’re doing in your code (that appears to me to be both efficient and clever).