How can I use fast FFT-based convolution to implement a LPF if the fast convolution requires a LPF?

Question

I\'m an experienced software engineer with some minor college DSP knowledge. I\'m working on a smartphone application to process signal data, such as from the microphone (sample

Answer 1

Microphones on smartphones always have analog low-pass filters prior to sampling. If aliasing already occurred in a signal, it is impossible to remove in general. For this reason every microphone's A/D converter has low-pass filtering implemented in alalog domain -- before discretization even occurs. Unless you yourself are downsampling or resampling the signal in some way, you should not worry about aliasing. Fast convolution and time domain discrete circular convolution are mathematically equivalent, so there's no reason for one to have aliasing if the other one does not have it.