resonanssi

Resonanssi, Finnish for resonance, is the phenomenon where a system responds with larger oscillation amplitudes at certain driving frequencies. A system has a natural or resonant frequency at which energy transfer between the driving force and the system is most efficient. When the driving frequency approaches this frequency, even small periodic forces can produce large responses if damping is small.

Common contexts include mechanical systems (pendulums, bridges, guitar strings) and acoustics (sound in air, air columns). When driven near resonance, amplitude increases and energy is stored and exchanged between kinetic and potential forms. Excessive resonance can cause damage or mistuning; damping reduces amplitude and broadens the resonance peak.

In electronics, resonance occurs in LC circuits where inductive and capacitive reactances cancel at the resonant frequency, causing minimal impedance in series circuits or maximal impedance in parallel circuits. This creates sharp peaks or dips in frequency response. The quality factor Q describes how narrow or broad the resonance is and is influenced by resistance and loss.

Resonance also appears in optics, molecular and atomic transitions (optical resonance), and in magnetic resonance techniques such as NMR and MRI, where transitions occur at characteristic frequencies in external fields.

Resonance is exploited for tuning radios and filters, musical instruments, and experimental measurements, but must be managed in engineering to avoid structural failure or unwanted excitation. It is analyzed using differential equations and linear systems theory, and measured via frequency response functions.