# [chuck-users] Simple question about getting a basic frequency spectrum

Lucas Samaruga samarugalucas at gmail.com
Thu Mar 4 22:36:32 EST 2010

```http://www.dspguide.com/ch8.htm

I need to read it too.

2010/3/5 Lucas Samaruga <samarugalucas at gmail.com>

> Hello v bar
>
> Just an approximation, I suggest a good book or internet resource.
> The polars you have are the magnitud (amp) and phase of each band of
> frequencies. The bands of frequencies you have are defined by the ratio
> between the sampling rate the windows size, that ratio is the analysis
> frequency. In this case, the analysis frequency is 44100 / 1024 =
> 43.06640625. Then you have windowssize / 2 = 512 harmonically related bands
> starting from 43.066 and... I strongly suggest a good reading, sorry I don't
> have nothing at hand right now.
>
> Best
> Lucas
>
>
> 2010/3/5 v bar <vomc8one at gmail.com>
>
> Hi,
>>
>> I am a little confused with fourier-transforms, math not being my
>> specialty.
>>
>> In essence all I am trying to do is take 1 second samples of an audio
>> file and print out coordinates as follows:
>>
>> - amplitude at 80Hz, amplitude at 200Hz, amplitude at 1000Hz
>>
>> I have set up a file connecting:
>>
>> SndBuf buf => dac;
>> buf => FFT fft  => blackhole;
>>
>> And now I assume that I set the fft.size to 1024 samples (for a 44k
>> 16bit audio file) and then upchuck that every 1024 samples.
>>
>> Most likely my error is there...
>>
>> But now I don't know how to get at the correct output.
>>
>> I have a ton of polar values but I don't really know what any of them
>> correspond to.
>>
>> Some sample values:
>>
>> "time: 0:5000.0000" : (string)
>> %(0.0140,-0.9985*pi) %(0.0004,-0.6629*pi) %(0.0001,-0.4812*pi)
>> %(0.0001,-0.4412*pi) %(0.0001,-0.7007*pi) %(0.0001,-0.7549*pi)
>> %(0.0001,-0.5928*pi) %(0.0000,0.7277*pi) %(0.0000,0.0000*pi)
>> %(0.0000,0.0000*pi) %(0.0000,0.0000*pi) %(0.0000,0.0000*pi)
>> "time: 0:6000.0000" : (string)
>> %(0.0189,0.0008*pi) %(0.0003,0.4507*pi) %(0.0001,0.2899*pi)
>> %(0.0001,0.2122*pi) %(0.0001,0.3072*pi) %(0.0000,0.5483*pi)
>> %(0.0001,0.1053*pi) %(0.0000,0.2292*pi) %(0.0000,0.0000*pi)
>> %(0.0000,0.0000*pi) %(0.0000,0.0000*pi) %(0.0000,0.0000*pi)
>> "time: 0:7000.0000" : (string)
>> %(0.0148,0.9997*pi) %(0.0002,0.4662*pi) %(0.0002,0.1996*pi)
>> %(0.0001,0.4250*pi) %(0.0001,0.2651*pi) %(0.0001,0.4396*pi)
>> %(0.0000,0.9036*pi) %(0.0001,0.4967*pi) %(0.0000,0.0000*pi)
>> %(0.0000,0.0000*pi) %(0.0000,0.0000*pi) %(0.0000,0.0000*pi)
>>
>>
>> Can someone help? I bet this is actually pretty simple I just can't
>> seem to figure it out. I understand the notion of polar coordinates
>> and know how I can convert them to Cartesian. But what I am not
>> understanding is where I find out what the actual frequencies that are
>> being sampled are...
>>
>>
>> Thanks
>> - J
>>
>>
>>
>> --
>> ---- vomc8one at gmail.com ----
>> _______________________________________________
>> chuck-users mailing list
>> chuck-users at lists.cs.princeton.edu
>> https://lists.cs.princeton.edu/mailman/listinfo/chuck-users
>>
>
>
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