I want to use sample rate 128
I use an example in ardiunofft that get sound by microphone and change sample rate 128 and sampling freqency 16000 then send a tone with 1000 hz but it can not determin freqency of it correctly
I want to determin amplitude of frequency in octav bands
So you changed "samplingFrequency = 100; //Hz, must be less than 10000 due to ADC" to 16000? Do you really think that 16000 is less than 10000?BTW even if you could use a sampling frequency of 16000 that would only work for audio frequencies up to 8000Hz. Anything over that present in the signal could cause all sorts of problems.Steve
I change samplingfrequency to another number also 8000
Was that graph something you produced or something you want? You have still not told us about your real application, that is what you will use that graph for.
What Arduino do you have?In order to see 20KHz you need to sample at least at 40KHz and preferably much higher.The project will require you know about FFT and windowing functions applied to the input waveform. I don't think it is something you can do with a Uno class Arduino.