Lead Bell

elastic modulus - quality of sound - resonance - Q

What it shows:
A lead bell, dull sounding at room temperature, rings brightly when cooled to liquid nitrogen temperatures.

How it works:
A lead bell at room temperature is dull in more ways than one. But its elasticity is temperature dependant, with an increase in elasticity as its temperature decreases. This increase in elastic modulus narrows the resonance response with frequency and increases the quality Q of the lead as an oscillator. Ringing the bell after its immersion in LN₂ excites resonance in a very narrow wavelength band, so giving a crisper sound.

figure 1 homemade lead bell

Setting it up:
Needs an accompanying flask of LN₂ and insulating gloves.

Comments:
Good accompaniment for other LN₂ dipped items in Everyday Objects at Low Temperatures, elasticity demos from Condensed Matter - Mechanical Properties, or resonance demos from Oscillations and Waves. Rating **

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