Pages: 1 2 [3]   Go Down
Author Topic: FFT on Arduino, the audio spectrum is cluttered?  (Read 3728 times)
0 Members and 1 Guest are viewing this topic.
Global Moderator
Netherlands
Offline Offline
Shannon Member
*****
Karma: 170
Posts: 12456
In theory there is no difference between theory and practice, however in practice there are many...
View Profile
 Bigger Bigger  Smaller Smaller  Reset Reset

@ aydingulgun
Please start your own thread and point to this thread (if needed), that way there is only one thread owner.

Thanks,
Logged

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

Offline Offline
Newbie
*
Karma: 5
Posts: 32
Don Bosley (b.1982) is an active composer, guitarist, and music technologist based in New York City.
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

You should read the appendix of the "Computer Music Tutorial" by Curtis Roads or Appendix C of my master's thesis: http://www.bosleymusic.com/Papers/DonBosleyThesis_06172013_Edit.pdf

Despite some good information in here, there seems to be some broad misconceptions about what the FFT does, and what the resulting numbers actually mean.
Logged

Lacey, Washington, USA
Offline Offline
Edison Member
*
Karma: 37
Posts: 1752
View Profile
WWW
 Bigger Bigger  Smaller Smaller  Reset Reset

A word on lowpass filtering for Nyquist: Nyquist essentially says that you should have no (negligible) frequency content at or above 1/2 the sample frequency.

So if the sample frequency is 39ksps, you can't just use an 18.5kHz cutoff filter, because that is only -3dB down at the corner frequency of 18.5kHz, and lets through quite a bit above that.

You need a lower corner frequency and a high enough order filter to drop down the filter passthrough to probably -40dB at 1/2 of the sample rate.
Logged

Steve Greenfield AE7HD
CET Consumer Electronics and Computer

Pages: 1 2 [3]   Go Up
Jump to: