I just got a nice message from a long-time member of this site, which reminded me of the whole purpose of this thread: SAFETY. There are plenty of areas where growers can skimp and save a few bucks, but safety is always #1 and the one area to never cut corners is on grow room security. You can cheap out on bulbs, nutes, grow with bag-seed, etc., but when it comes to sound and odor control, every reasonable precaution should be taken. Considering the minimal additional cost of upgrading to specialized soundproofing insulation (~10%), it would be silly for anyone that needs to stay quiet to not spend the extra few bucks and help keep things silent.
This is very much like using a trusted name brand carbon filter vs. a cheap made in China filter.......The cheap filter is $80 cheaper, but only works 50% as well (I know from experience, a mistake I made on my first grow). Is it really worth saving $80 when your safety and freedom is on the line? There are a TON of unnecessary expenditures when it comes to growing, and plenty of ways to save money.....I know, I'm a cheap old bastard myself. Just remember that safety and security is #1 and that an extra $50-80 spent on a brand name filter, or upgraded sound-proofing is a lot cheaper than one phone-call to a lawyer.