Which electrical circuit produces a decaying alternating current wave in response to a pulse?
Also examine a resonant circuit with Fresonate at 1/2 the pulse frequency.
And slightly vary the pulse frequency. You'll see the effects of energy building and cancelling within the same period of ringing.

By the way, this really occurs. The phenomena brings up the question of "What are harmonics?"

For those without SPICE, or not wanting to learn SPICE, the tool Signal Wave Explorer SWE is available for free download. There are 14 canned examples, with only 3 mouse clicks to select and run. Then you can edit params, to place the pulse frequency exactly at Fresonate, or at 1/2 Fresonate. And rerun.

The tool uses Fourier Analysis (behind the scenes) to compute the output waveform, given input waveform and circuit frequency/phase response. 
By default, you'll see input waveform, input spectrum, circuit spectrum, output spectrum and output waveform.

Here are 120MHz impulses into a 300MHz resonator, Q=10