User Manual
Slam Stick User Manual
Version No. 2.0
52
Figure 26: The PSD (power spectral density) window is useful for comparing data to test standards, especially when
a dataset is made up of many frequencies.
Slam Stick Lab can calculate the PSD in two ways, a full calculation or a windowed calculation. A
full calculation will operate on the entire range with a single FFT and no windowing. A windowed
operation will divide the signal into windows of exactly the selected size, throwing out any data
that does not fit into a window. A Hanning window function is then applied to each window, the
FFT is applied to the result, and the PSD is taken. A windowed PSD uses less computational power
and memory, and results in cleaner looking data because it is an average of data sets. Note the
windowed calculation may miss data at the end of a signal that does not fit into a window, and
windowed and full calculations will result in different frequency bin widths. See our
windowing and frequency leakage
Spectrogram
A spectrogram takes a series of FFTs to provide an illustration on how the frequency content is
changing with time. The user can select how many “slices” per second for the spectrogram. Each
slice has a Hanning window applied to generate smoother data. For more information, visit our