The Short Time Fourier Transform (STFT) is a function of both time (frame number ) and frequency ( ). It is therefore an example of a time-frequency distribution. Others include
The uniform and rectangular nature of the STFT time-frequency tiling is illustrated in Fig.7.1. The window length is proportional to the resolution cell in time, indicated by the vertical lines in Fig.7.1. The width of the main-lobe of the window-transform is proportional to the resolution cell in frequency, indicated by the horizontal lines in Fig.7.1. As detailed in Chapter 3, choosing a window length and window type (Hamming, Blackman, etc.) chooses the ``aspect ratio'' and total area of the time-frequency resolution cells (rectangles in Fig.7.1). For an example of a non-uniform time-frequency tiling, see Fig.10.14.