C.4.5—Damping and resonance

Read the response peak

Damping removes mechanical energy from an oscillator. On an amplitude-versus-driving-frequency graph, increasing damping lowers the maximum amplitude and makes the peak less sharp. The resonant frequency also shifts slightly to a lower value. These are qualitative changes; the syllabus does not require a detailed damped-oscillator derivation.

Connect damping to energy

More damping means more energy is dissipated during each cycle. The driver must supply that lost energy, but the oscillator cannot build up as large an amplitude before input and loss balance. With little damping, energy accumulates more efficiently and the resonance peak is taller and narrower.

Apply the model

If a suspension or bridge is damped, the oscillation amplitude is reduced and the resonant response occurs at a slightly lower driving frequency. This can be useful for controlling vibration, although damping also reduces the sharpness of frequency selection.

Common trap

Do not draw a damped response with a taller peak. More damping lowers the peak and shifts it left on a frequency axis whose driving frequency increases to the right.