antiresonances

Antiresonance is a phenomenon in which a system exhibits a minimum, or even zero, response at a particular frequency. It is commonly described as a zero of the system’s transfer function and is the counterpart to resonance, where the response is maximized. Antiresonances arise when different pathways of energy transfer interfere destructively or when impedances cancel at a specific frequency. They are not simply the result of heavy damping or weak forcing, but reflect the internal structure and coupling within the system.

In mechanical and electrical systems, antiresonances often appear in multi-degree-of-freedom configurations. For example, in a two-mass–spring–damper system, the transfer from input to a second mass can have a zero between the two natural frequencies, producing a pronounced dip in the response. In electrical engineering, notch or band-stop filters are designed to create antiresonant frequencies where the output is strongly attenuated, corresponding to zeros in the voltage or current transfer function.

Antiresonances also occur in acoustics, optics, and quantum systems. In acoustics, layered materials can display antiresonant frequencies that suppress certain sound wavelengths. In quantum physics, Fano interference produces antiresonant dips in transmission as a discrete state interferes with a continuum.

The position and depth of an antiresonance depend on system parameters such as stiffness, mass, coupling, and damping. They can be used deliberately to design filters, suppress unwanted vibrations, or probe the internal coupling structure of a device.