When a vibrating tuning fork is placed in a vacuum jar and the lid is repeatedly opened and closed, listeners can perceive a single continuous sound being revealed rather than a series of discrete, newly created sounds.

To develop this line of thought and make it vivid, imagine a vacuum jar which has the property of immediately creating a vacuum upon closing the lid, and of immediately recalling air upon opening the lid. Take now a sounding object like a tuning fork at 440Hz and have it vibrate, supposing that the vibration fades and becomes inaudible after 10 seconds. What you hear is an A that becomes feebler and feebler until it disappears. Now, place the tuning fork inside the jar, have it vibrate as before