For italian people:

Slinky è il nome commerciale di questo giocattolo, formato da una lunga molla elicoidale, in voga (boh) forse 20-30 anni fa (è stato inventato negli anni ’40; io ne ho almeno 4/5, ma non ricordo quando le ho comprate).

Vedi anche wikipedia.

A sound wave in a long wire travels back and forth and produces an echo effect. This fact was well known to the old sound engineers and the so called spring reverberator was largely used in the analogical era.

In this video micolich shows the power of long springs. When touched, the sound travels repeatedly along the whole length of the spring producing a stream of little echoes with decreasing amplitude. But the sound speed is high, so the time distance between echoes is a question of milliseconds. As result we can’t perceive the single echo, but a decreasing halo that extend the sound: this is the reverberation.