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

The low pass filter must be placed before the ADC, i.e. it must be an analog circuit of some kind. You cannot remove the aliases from the sampled signal because you do not know which part of the sampled signal is due to aliasing, that is the whole point of why aliasing is a problem.