Also, it's not as widely known as the FFT, but if you know roughly the frequency of interest you can use the Goertzel algorithm to calculate a chosen number of bins around that specific freq and then pick the max of them to find the freq of interest, instead of when using the FFT having to calculate a bunch of bins using a large nFFT in order to get enough freq resolution and then discarding 99% of the results. Going further, compared to the original Goertzel, the Generalized Goertzel algorithm does the same thing but allows you to query non-integer multiples of the fundamental frequency: http://asp.eurasipjournals.com/content/2012/1/56