How does Matlab handle timing ?

[Element_115]

matlab function daqfcngen

Hi Genz

I was trying to tune my guitar so I wrote a matlab program to
generate a 440Hz tone . (So I thought)

t=1:05:10; % 10 Seconds (time)
y=sin((440*t/(2*pi)); % sin is in rad's
sound;
%%%%%%%END%%%%%%

The tone sounds close to 440Hz but the length
was not 10 second only about 1 or 2.
Can anyone tell me how Matlab handles time.
Or is this a processor based issue, and I should
just do trial and error?

Thanks

 

[Gemini1706]

y=sin((440*t/(2*pi));

This is worng..

y=sin(440*2*pi*t); % This is correct..

Note that w=2*pi*f, but you used w=f/(2*pi) which is not correct..

good luck..

 

[cesariv]

Timing in Matlab?

You need to define a frequency sample(Fs), Fs tells matlab, the time to reproduce a single sample.
In accordance with your code t=1:0.5:10, you are using a Fs=1/0.5, so you must give to the sound command the same Fs.

Plus, you have to fix the formula
good luck

 

[nebisman]

Re: Timing in Matlab?

Yes

additionally you have to choose very fast sampling rate for t for a pure sinusiodal waveform

for these you can use a t=0:1/8192:10 sampling rate for radio quality. This is about 20 point for cycle of wave.

I don't konw if you have in your version of matlab the DAQ toolbox, if you have it use the daqfcngen function see the help

for this purpose you can use a signal generator software (I remember siggen) which you can find easyly in the web.

 

[Element_115]

Re: Timing in Matlab?

Thanks for your help!
I did initially use (2*Pi*F*t) but this produced too high of a frequency.
So I played around and the code I showed was close to 440Hz.
I will look into the DAQ help file. But if I use Fs=100KHz (5*20KHz)
how do I know that "1: (1/100000) : 10" will be ten seconds? Is there
a WAV file format that determines Fs?...

Thanks