Old alarm clocks and many doorbells and telephones emit a signal due to the blows of “hammer” metal hemisphere of the bell.
If you are annoying it’s pretty sharp rattling, stick a bell in place of hitting it square of adhesive tape or medical adhesive tape device will beep “whisper”.
.
Recommend to read
“Cocoon” on the snow
At the end of winter in 1974, on snow-covered fields near the airport “Domodedovo”, an unusual machine appeared—something like the egg of a fairy bird Rukh, or like a gigantic cocoon....
UNIVERSAL INDICATOR
Two LEDs with different color (e.g., red and green), you can build a simple indicator for voltages from 4.5 to 220 V. It is also able to determine the polarity of the source in the range...
