Aliasing describes the production of an artificially long wavelength due to slow periodic sampling of a periodic signal. To reproduce the signal accurately, the sampling frequency should be at least slightly larger than twice the highest frequency contained in the signal (a.k.a. the Nyquist frequency). For example, if the sampling rate is 2b then all frequencies less than b will not be aliased.

Band Pass Filters will filter out certain wavelengths to allow the user to focus on different parts of the signal. A low pass filter removes wavelengths smaller than the user-defined cutoff and leaves the longer wavelengths unaffected. A high pass filter will remove larger wavelengths and leaves the shorter wavelengths unaffected. A bandpass will only allow wavelengths through between two frequencies cutoff, and can be constructed from a combination of low pass and high pass filters. The bandpass is described by the Quality (Q) factor, where high Q describes a narrow pass band.

Credit: SpinningSparks