1. A signal pre-processing method comprising: obtaining an input signal comprising a tonal noise peak; smoothing the input signal in a frequency-based direction to attenuate the tonal noise peak in the input signal and obtain a smoothed signal, where smoothing the input signal comprises: determining a first windowed average of the input signal to obtain a first averaged signal; determining a second windowed average of the first averaged signal by selecting a window of signal components starting at an index point in the first averaged signal; comparing at least one of the signal components to the first windowed average of the input signal at the index point to identify an outlying signal component that exceeds the first windowed average of the input signal at the index point; and excluding the outlying signal component in determining the second windowed average; obtaining a background noise estimate; and blending the smoothed signal with the input signal based on the background noise estimate to obtain an output signal, where blending comprises: outputting the input signal as the output signal in response to a determination that the background noise estimate satisfies a first predetermined condition; and outputting the smoothed signal as the output signal in response to a determination that the background noise estimate satisfies a second predetermined condition different than the first predetermined condition.