More than one frequencies

I am trying to understand how multiple tone-frequencies work. I'd like to find the boundary where it still sounds like two tones and where it sounds like only one tone.

I'm trying to understand how I set a constant frequency to each of the sounds.

I'd like them to play atleast one minute, to hear how close are they to sound like one tone.

Answer 1

[Star Strider]

Multiply the two tones (modulate the 440 Hz with the 400 Hz) to get the ‘beat’ effect you want:

sound(s, Fs)                                    % Produce Tone As Sound1
pause(1.5)
sound(s1, Fs)                                   % Produce Tone As Sound2
pause(1.5)
sound(s.*s1, Fs)                                % Modulate To Produce Desired ‘Beat’ Effect

.

[Anonym]

Thanks for the help :)

Based on that code, how can you adjust it so that it may not be playing at the same time, but maybe a second behind or a completely different number?

Because, I need to have a number on how close the frequencies of the two tones must be to each other before they no longer sound as two tones, but as one tone with vibrato.

[Star Strider]

My pleasure!

Multiplying them together will produce the ‘beat’ result you want:

sound(s.*s1, Fs)                                % Modulate To Produce Desired ‘Beat’ Effect

They will not modulate (produce the ‘beat’ of the two frequencies) if simply play at the same time. Instead, they will just sound like two different tones. You can make one out-of-phase with the other most easily by adding zeros to the beginning of one of them, if you want to play the two tones simultaneously.

Note that they would have to be the same lengths to use my multiplication operation, so the third option would not work if one were zero-padded.

Also, the will have the correct sound and duration using:

t  = linspace(0, Fs, Fs);                        % One Second Time Vector

.

[Anonym]

I think I got it, thank you. But what does the linspace command entail, what do the three parameters in the command mean? Why do we use sampling frequency, is it important in this case?

Sorry, I probably sound silly. Trying to make it clear in my little brain ;-).

[Star Strider]

My pleasure!

Sampling frequency is important here because that guarantees that the sounds will be accurate and correct. There are other ways to do it using linspace, however here this is the easiest.

[Anonym]

Thanks alot. Sorry for disturbing again :-) Is it possible to generate a plot of this. I tried this, didn't work.

plot(s,s1);   %https://se.mathworks.com/help/matlab/ref/plot.html

How should I write the parametres?

[Star Strider]

It actually did work. It plotted a Lissajous figure, however the points are too dense to see any of the detail.

I suspect you want something like this:

t  = linspace(0, Fs, Fs);                        % One Second Time Vector

then:

figure
subplot(3,1,1)
plot(t, s)
xlim([0 1E+3])
grid
subplot(3,1,2)
plot(t, s1)
xlim([0 1E+3])
grid
subplot(3,1,3)
plot(t, s.*s1)
xlim([0 1E+3])
grid

Note that the third subplot clearly shows the ‘beat’ effect of mixing the two signals. It would be more readily apparent if tthe signal frequencies were farther apart.

[Anonym]

Thank you very much, understanding it better now :D

Yeah, it gave me a blue screen, thought it meant nothing.

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

.

[Anonym]

Did it, also last thing what do we have to change, so the signal frequencies were farther apart? The only part, I can think of is the linspace?

[Star Strider]

Thank you!

I would change the ‘400’ to something higher, that would give the effect you want. A frequency (carrier frequency) of 1500 is a likely starting place. The only constraint is that both frequencies should be within the range of human hearing, perhaps 10 kHz being the practical upper limit, although human hearing ranges up to about 20 kHz (thus the 44100 Hz sampling frequency for CDs).

[Anonym]

Hey Star Strider, I'm really sorry for disturbing all the time. I am working on a project in Matlab, which deals with stain removal. However, I have a small problem as I have stated here: https://se.mathworks.com/matlabcentral/answers/645008-illustrate-that-products-of-the-form-cxv-give-the-same-results-as-dct-v.

Wanted to hear if you could look into it?

Thanks, best regards AU.

[Image Analyst]

I've been working on stain removal for literally the past 28 years.

[Star Strider]

Anonym — Image processing is not an area of my expertise. I have done some, however only for medical images with respect to my own work. I cannot help you with that.

Answer 2

[Image Analyst]

For what it's worth, I'm attaching a demo: