antiresonance

Antiresonance is a frequency at which a system’s response to an external drive or input is minimized due to destructive interference between alternate pathways of motion or signal transmission. It is the counterpart to resonance, where the response is maximized. In many contexts, antiresonance corresponds to a zero of the transfer function, meaning the output vanishes for a particular input frequency, even though nearby frequencies may produce strong responses.

In mechanical systems, antiresonance often appears between two resonance peaks in a system with coupled oscillators or multiple pathways for energy transfer. The contributions of different modes cancel at a specific frequency, yielding a pronounced dip in the measured response—such as displacement or velocity—despite ongoing excitation.

In electrical circuits, antiresonance occurs when a network produces a transmission minimum at a certain frequency. Notch or band-stop filters exploit antiresonant frequencies to suppress signals. Depending on topology, antiresonance can manifest as a zero of the transfer function from input to output, or as an impedance extremum associated with a cancellation of currents through parallel paths.

In quantum systems, antiresonance (often described in the context of Fano interference) refers to a zero in the transmission amplitude resulting from the interference between a discrete quantum state and a continuum. This can produce sharp dips in conductance or other observable quantities.

Antiresonance is useful for designing vibration suppression, filter shaping, and sensing applications, where deliberate cancellation of motion or signal at specific frequencies is desirable.