What is it about lead that makes it good for soundproofing
Stretching the memory cells to a previous life so forgive me if I err in the detail.
Lead usually is in the form of lead wool. Weighs a bit but does a fine job in dampening a reasonable frequency spectrum of noise.
Higher frequency noise attentuates well in light material such as fibreglass batting, lower frequency needs some mass to vibrate.
soundproof chamber
anechoic chambers use multifaceted foam wall sections to disperse and attenuate incident sound energy. Try not to get caught in one over the weekend, though ... the sensory underload is quite stressful as the odd victim has observed.