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How to plot absorption of sound waves in seawater and boric acid?

Asked by Junaid Qadir on 6 Oct 2019
Latest activity Commented on by Junaid Qadir on 8 Oct 2019
Please provide a Matlab code for the figure below.
a.png

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1 Answer

Answer by Stephan
on 6 Oct 2019
 Accepted Answer

% Produce some data
x = logspace(-1,2);
y1 = exp(x);
y2 = (exp(x)./exp(y1));
% Plot lo double log-scale
loglog(x,y1,'--k','LineWidth',2)
hold on
loglog(x,y2,'-k','LineWidth',2)
hold off
% Change look
a = gca;
grid on
xlabel('Frquency - kHz')
ylabel('Attenuation - dB/km')
legend({'Saltwater', 'MgSO_{4}'}, 'Interpreter', 'tex', 'Location', 'southeast')
a.GridLineStyle = '--';
a.MinorGridLineStyle = '--';
a.GridColor = 'k';
a.MinorGridColor = 'k';
a.GridAlpha = 1;
a.MinorGridAlpha = 1;

  6 Comments

you might want to plot a parametric curve. Here is an example:
As already pointed out, you will need the equations or data to plot your curve.
Thank you so much for your kind help.
Dear Stephan, please see code below and kindly let me know where is the problem occuring? Why the plot does not draw? I think there is some missing of ''for loop''.
%************* Junaid Qadir *************%
%************* MPhil Electronics *************%
%************* Department of Electronics *************%
%************* Quaid-i-Azam University Islamabad,45320, Pakistan *************%
% %************* Email: jndqadar@gmail.com , Instagram: @junaid_qadar, Facebook: https://web.facebook.com/junaid.qadar*************%
%%%%%%%%%%%%% BORIC ACID + Magnesium sulphate+ Pure water
clear all
close all
clc
f= 30; % kHz
S= 35; % salinity
T=10; % temmperature in degree centi grad
pH= 7.8;
theta= 273+T;
D= 500; % Depth in meter
c = 1449 + 4.591 *T - 5.304 * 10^(-2)*T^(2) + 2.374 * 10^ (-4) * T^(3) + 1.34*(S - 35) ...
+ 1.63 * 10^(-2) * D + 1.675 * 10^(-7)* D + 1.025* 10^(-2)* T*(S - 35) - 7.139* 10^(-3)*T*D^3; % Sound Speed in water = 1500 m/s
p1= 1; % pressur 1
p2= 1-1.37* 10^(-4) *D +6.2*10^(-9)* D^2; % pressure 2
p3= 1-3.83*10^(-5) * D+4.9*10^(-10) *D^2; % Pressur 3
f1= 0.78* sqrt(S/35)*10^(T/26); % frequency 1
f2= 8.17*10^(8-1990/theta); %fruency 2
A1= 8.86/c*10^(0.78*pH-5); % Absorption
A2= 21.44* S/c*(1+0.025*T); % Absorption
A3= 3.964*10^(-4)- 1.146* 10^(-5)*T +1.45*10^(-7)*T^2-6.5*10^(-10)*T^3; % Absorption
Boric_acid= A1*p1*f1*f/ f1^2*f^2; % Formula for Boric acid
Magnesium_sulphate= A2*p2*f2*f^2/ f2^2+f^2; % Formula for Magnesium sulphate
Pure_water= A3*p3*f^2; % pure water
Total= Boric_acid+ Magnesium_sulphate + Pure_water; % Total Absorption
% Plot to double log-scale
loglog(Boric_acid,f,'--r','LineWidth',2)
hold on
loglog(Magnesium_sulphate,f,'-*k','LineWidth',2)
hold on
loglog(Pure_water,f,'-.*g','LineWidth',2)
hold on
loglog( Total,f,'--hb','LineWidth',2)
hold off
% Change look
a = gca;
grid on
xlabel('Frquency - kHz')
ylabel('Attenuation - dB/km')
legend({'Boric acid', 'MgSO_{4}', 'Pure water ', 'Total absorption'}, 'Interpreter', 'tex', 'Location', 'southeast')
a.GridLineStyle = '--';
a.MinorGridLineStyle = '--';
a.GridColor = 'k';
a.MinorGridColor = 'k';
a.GridAlpha = 1;
a.MinorGridAlpha = 1;

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