FFT Frequency Resolution and Window Length

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Fs (Hz) FFT length (samples)
16384 8192 4096 2048 1024 512 256 128 64
8000 0.48 0.97 1.95 3.90 7.81 15.62 31.25 62.50 125.0
11025 0.67 1.34 2.69 5.38 10.76 21.53 43.06 86.13 172.3
16000 0.97 1.95 3.90 7.81 15.62 31.25 62.50 125.00 250.0
22050 1.34 2.69 5.38 10.76 21.53 43.06 86.13 172.26 344.5
32000 1.95 3.90 7.81 15.62 31.25 62.50 125.00 250.00 500.0
44100 2.69 5.38 10.76 21.53 43.06 86.13 172.26 344.53 689.1
48000 2.93 5.85 11.71 23.43 46.87 93.75 187.50 375.00 750.0
64000 3.90 7.81 15.62 31.25 62.50 125.00 250.00 500.00 1100.0
88200 5.38 10.76 21.53 43.06 86.13 172.26 344.53 689.06 1378.0
96000 5.85 11.71 23.43 46.87 93.75 187.50 375.00 750.00 1510.0

Table 10: Effective window duration (ms), depending on sampling frequency (FS), FFT-frame and time window length

Fs (Hz) FFT length (samples)
16384 8192 4096 2048 1024 512 256 128 64
8000 1024.00 512.00 256.00 128.00 64.00 32.00 16.00 8.00 4.00
11025 743.03 371.51 185.76 92.88 46.44 23.22 11.61 5.80 2.90
16000 512.00 256.00 128.00 64.00 32.00 16.00 8.00 4.00 2.00
22050 371.51 185.76 92.88 46.44 23.22 11.61 5.80 2.90 1.45
32000 256.00 128.00 64.00 32.00 16.00 8.00 4.00 2.00 1.00
44100 185.76 92.88 46.44 23.22 11.61 5.80 2.90 1.45 0.72
48000 170.66 85.33 42.66 21.33 10.66 5.33 2.66 1.33 0.66
64000 128.00 64.00 32.00 16.00 8.00 4.00 2.00 1.00 0.50
88200 92.88 46.44 23.22 11.61 5.80 2.90 1.45 0.72 0.36
96000 85.33 42.66 21.33 10.66 5.33 2.66 1.33 0.66 0.33

Table 9: .Frequency bin resolution (DHz) depending on sampling frequency (FS), FFT-frame and time window length.Note 1: in order to obtain the frequency resolution values and window lengths listed above in an STx analysis, specify either the Df-value bandwidth [Hz] or spectrogram frame length [ms]*2 in the Setup dialogue of the spectrogram..Note 2: optional Df-values (such as the bandwidth of exactly 1 Hz) not shown in the table above are available on request applying DFT instead of FFT.