[OneDeuxTriSeiGo]

It's because lead has one of the lowest modulus of elasticity of the elements but also has a very high density. So at room temperature it doesn't have any resonant frequencies and has so much mass that it can effectively damp frequencies traveling through it. And you can see this with the lead bell experiment.

The only metals with a lower E are far more expensive or are extremely difficult to work with because they like to catch fire or explode when exposed to water or oxygen or react with any other element they touch. Or they are radioactive.

The "non problematic" elements better than lead are indium, thallium, and selenium. Selenium has toxicity issues (albeit less than lead) and indium and thallium both have low melting points and become increasingly soft/lose their form even at low industrial temperatures. And of course all three are far far more rare than lead and often are produced as byproducts of mining for lead and occasionally other metals.

And there are non-metal options that don't resonate near room temperature like many of the plastics and rubbers but they lack the density/mass to effectively damp vibrations from neighboring components.

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https://www.youtube.com/watch?v=SFGlTGMlyqM

https://sciencedemonstrations.fas.harvard.edu/presentations/...