Hai to all, Iam new to this forum and dsp. Iam involved in converting a 5sec voice to frequency using a fft. Using pic24f series i need to accomplish this. Can anyone guide through this process? What should be my sampling rate, How can i convert the digital samples into real and imaginary parts, since the c coded fft requires real and imaginary parts as arguments to fft.How many point fft should i implement? Please help me through. Thanks in advance, Siva

# conversion of voice to frequency domain using fft

Started by ●October 21, 2008

Posted by ●October 21, 2008

sivaramakrishna wrote:> Hai to all, > Iam new to this forum and dsp. Iam involved in converting a 5sec voice > to frequency using a fft. Using pic24f series i need to accomplish this. > Can anyone guide through this process? What should be my sampling rate, How > can i convert the digital samples into real and imaginary parts, since the > c coded fft requires real and imaginary parts as arguments to fft.How many > point fft should i implement? > Please help me through. > > Thanks in advance, > SivaSorry for my bad english, i am here in germany First, You need a low-pass filter. Then your sample rate has to be faster than twice the maximum frequency which comes throug your filter. For the calculation, you can simly take the imagimary values of the input signal as zero. With FFT, you then get a complex spectrum. From this, you can calculate the power-spectrum by x = const *(real*real + imag*imag). Stefan

Posted by ●October 22, 2008

>sivaramakrishna wrote: >> Hai to all, >> Iam new to this forum and dsp. Iam involved in converting a 5secvoice>> to frequency using a fft. Using pic24f series i need to accomplishthis.>> Can anyone guide through this process? What should be my sampling rate,How>> can i convert the digital samples into real and imaginary parts, sincethe>> c coded fft requires real and imaginary parts as arguments to fft.Howmany>> point fft should i implement? >> Please help me through. >> >> Thanks in advance, >> Siva > >Sorry for my bad english, i am here in germany > >First, You need a low-pass filter. Then your sample rate has to be >faster than twice the maximum frequency which comes throug your filter. > >For the calculation, you can simly take the imagimary values of the >input signal as zero. With FFT, you then get a complex spectrum. From >this, you can calculate the power-spectrum by x = const *(real*real + >imag*imag). > > >Stefan >My pic24f controller has a 22k program memory and 8k data memory. I need to implement a fft with this hardware. So please find me a c code for fft which makes the micro controllers performance optimum. Thanks, Siva

Posted by ●October 22, 2008

"sivaramakrishna" <siva.gram@gmail.com> wrote in message news:8_mdnTybNJKVSGPVnZ2dnUVZ_i2dnZ2d@giganews.com...> > My pic24f controller has a 22k program memory and 8k data memory. I need > to implement a fft with this hardware. So please find me a c code for fft > which makes the micro controllers performance optimum.No Google in India?? Meindert

Posted by ●October 22, 2008

>"sivaramakrishna" <siva.gram@gmail.com> wrote in message >news:8_mdnTybNJKVSGPVnZ2dnUVZ_i2dnZ2d@giganews.com... >> >> My pic24f controller has a 22k program memory and 8k data memory. Ineed>> to implement a fft with this hardware. So please find me a c code forfft>> which makes the micro controllers performance optimum. > >No Google in India?? > >Meindert > > >But i could not find a one which suits my requirement. Siva

Posted by ●October 22, 2008

"sivaramakrishna" <siva.gram@gmail.com> wrote> But i could not find a one which suits my requirement.Look for any FFT code on the web like fftw (google+fftw) Don't forget to put an antialiasing filter or you will get spectrum overllaping! For voice signal 3kHz filter should be fine, and you should sampe with at least 7kHz ! Number of samples depend on you're wanted physical spectrum resolution. For radix-2 algorithm try 64/128/256 and see what suits you best. Also, it would be great to learn basics of DSP :) Greetings from Croatia from a student!