Frequency analysis : relation between FFT size and sampling I am currently trying to perform an experiment given an audio signal. I am therefore sampling the audio frequency range (0 to 22kHz) with a 48k sampling rate. 

When performing a FFT on my signal, I had the following question :


Is it equivalent to have a very small FFT size (for example 256), producing a 172 Hz resolution on my signal, in comparison with having a large FFT size (in a way more bars..) and performing a mean on my resulting frequencies in order to bring the number of bars down?
The two are not equivalent. Taking a larger FFT means you are using more time domain samples (unless you zero pad), in which case you have introduced new information compared to a smaller FFT size