Signal Processing & DSP

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Aliased Frequency

Frequency an under-sampled tone masquerades as.

Formula

f_a = |f - n f_s|

Variables

f_aAlias frequency (Hz)

fTrue frequency

nNearest integer multiple

f_sSampling rate

Example

f=30 kHz sampled at 44.1 kHz: alias ≈ 14.1 kHz

Did You Know?

Aliasing is why wagon wheels appear to spin backwards on film — the frame rate under-samples the motion.

dsp aliasing sampling

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Nyquist Rate

Sample at least twice the highest frequency to avoid aliasing.

FFT Bin Frequency

Frequency represented by the k-th bin of an N-point FFT.

Frequency Resolution

Spacing between adjacent FFT bins.

Signal-to-Noise Ratio

Ratio of signal power to noise power, in decibels.

Quantisation SNR

Best possible SNR (dB) of an ideal b-bit converter.

Decibel (Power Ratio)

Express a power ratio in decibels.