Okay I have a question involving calculating the FFT of a signal from a sensor. I have simulated many different scenarios in MATLAB of various noise characteristics involving the signal. I want to take the FFT of a noisy signal. As long as my expected input signal has a higher amplitude than noise signals of other frequencies, then the plotted spectrum of the magnitude of the signal should always have the highest peak at my expected input signal's frequency, is this correct? The reason I am asking is due to an argument about whether filtering is needed to discover the expected input signal's frequency. If the amplitude of the the input signal is always higher, I figured it would always be the peak of the magnitude spectrum. If this is not correct, what is a correct way to look at this scenario?