Anyone know anything about tremolos?

[JohnCU]

I'm supposed to write a Matlab program to produce a tremolo (for ECE homework). This is what I got so far...

freq=input('Specify frequency (Hz): ');
rfreq = 2*pi*freq;
tSpeed=input('Specify tremolo speed (s): ');
tDepth=input('Specify tremolo depth (0 < depth < 1): ');
Ts=[linspace(0,4,8192*4)];
signal = cos(rfreq*Ts);

I know I gotta somehow have another signal that envelopes that first signal, so that it the loudness fades in and out but I'm not sure how...?

 

[TuxDave]

I forgot what a tremolo is. But if you want to adjust the loudness, why not multiply your signal with what you want as your tremolo?

signal = (1-cos(tremfreq*Ts))*cos(rfreq*Ts)... kinda like amplitude modulation.

 

[JohnCU]

I wish the mods wouldn't have moved this, it's more about the math of creating a tremolo than programming...

 

[TuxDave]

I was wondering where this thread went. So for a violin, can you describe the act of a tremolo? I think I can offer ideas then.

 

[JohnCU]

The loudness varies. Loud->low->loud->low, it's alternating patterns of higher and softer tones I guess.

like WOOOO, woooo, WOOOOO, wooo...

 

[TuxDave]

So I'm guessing you want something very similiar to amplitude modulation. So instead of having a constant amplitude.

Amplitude*cos(freq*Time), you want to make your amplitude a function of time. So it'll look like.

(1-depth*cos(tremfreq*Time)).*cos(rfreq*Time). So now your signal will be enveloped by your trembolo function.

 

[JohnCU]

Thanks a lot man!

 

[JohnCU]

Now here's a bigger question, how do you decay the tremolo so that the fading in and out decays, but the signal keeps going, it just doesn't change loudness (it evenutally levels off).

I know I can multiply the signal by e^(-T/Time Constant), but that decays the whole signal to 0...