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The measures of the quality of an FFT window function are:
Sidelobe level, fall offand 6 dB bandwidth measure a window function's quality in terms of resolving close frequency components.
Coherent Power Gain measures the amount by which a frequency component's measured value is attenuated by the window function
Equivalent Noise Bandwidth and Worst Case Processing Loss measure a window function's quality in terms of detecting a signal in noise.
| Window function | Sidelobe (dB) | Fall off (dB/octave) | Coherent Power Gain | Equivalent Noise Bandwidth (FFT bins) | 6 dB bandwidth (FFT bins) | Worst Case Processing Loss (dB) |
| Rectangular | - 13 | - 6 | 1.00 | 1.00 | 1.21 | 3.92 |
| Triangular | - 27 | - 12 | 0.50 | 1.33 | 1.78 | 3.07 |
| Hanning | -32 | -18 | 0.50 | 1.50 | 2.00 | 3.18 |
| Hamming | - 43 | - 6 | 0.54 | 1.36 | 1.81 | 3.10 |
| Poisson (3.0) | - 24 | - 6 | 0.32 | 1.65 | 2.08 | 3.64 |
| Poisson (4.0) | - 31 | - 6 | 0.25 | 2.08 | 2.58 | 4.21 |
| Cauchy (4.0) | - 35 | - 6 | 0.33 | 1.76 | 2.20 | 3.83 |
| Cauchy (5.0) | - 30 | - 6 | 0.28 | 2.06 | 2.53 | 4.28 |
| Gaussian (3.0) | - 55 | - 6 | 0.43 | 1.64 | 2.18 | 3.40 |
| Kaiser-Bessel (3.0) | - 69 | - 6 | 0.40 | 1.80 | 2.39 | 3.56 |
| Kaiser-Bessel (3.5) | - 82 | - 6 | 0.37 | 1.93 | 2.57 | 3.74 |
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| Last updated: 29th January 1998 | http://www.bores.com/courses/advanced/windows/10_end.htm