minimumfrequency

Minimum frequency is a term used in several technical contexts to denote the lowest frequency component, or the lower bound of a frequency range, relevant to a signal, system, or measurement.

In signal processing, the minimum nonzero frequency component of a signal is often called the fundamental frequency. For a periodic signal with harmonic content, the fundamental f0 is the greatest common divisor of the spectral lines. If the signal is not strictly periodic or if one analyzes a finite record, the practical notion becomes the lower limit of the spectrum, with frequency spacing roughly Δf = 1/T for a record of duration T. The DC term at 0 Hz is sometimes excluded from discussions of minimum frequency.

In filtering and communications, f_min typically denotes the lower cutoff frequency of a bandpass or channel; frequencies below f_min are attenuated or rejected. In audio and acoustics, the usable low end of the spectrum is constrained by equipment, transmission medium, and human hearing, commonly referenced around 20 Hz as the lower bound of audible frequencies.

In data analysis and spectral estimation, the minimum frequency resolvable from a finite time series is approximately 1/T, and practical analyses may impose additional lower limits based on windowing and noise considerations.

Practical considerations often require clear specification of what is meant by minimum frequency: the fundamental of a signal, the spectral lower bound, or the filter’s cutoff. See also fundamental frequency, lower cutoff frequency, Nyquist frequency, and spectral resolution.