5 ms·
But physically, if you put a 30 db noise reducer behind another 30 db noise reducer, you will get 60 db noise reduction overall.
by sp332 3y ago
But physically, if you put a 30 db noise reducer behind another 30 db noise reducer, you will get 60 db noise reduction overall.
- TylerE 3y agoBut you can’t! Sound waves have many paths to the eardrum and related tiny bones.
- Retric 3y agoThat applies when sound has a secondary path through the body. But not all noise reduction just cover the ears. Someone standing in a box with earmuffs could see 30 + 30 = 60db drop for some frequencies. As would someone standing far enough from a sound to see 30db drop off who then uses non distance related ear protection.
- kazinator 3y agoI predict that TylerE will not believe you.
- TylerE 3y agoNeither does osha. They spec that when earring muffs and plugs the effective rating is the higher rated product +5db.
- kazinator 3y agoNote that this estimate disagrees with the wholly inappropriate calculator you cited, which will never produce a value exceeding the higher value by more than 3 dB. OSHA almost certainly had to empirically determine the estimate, either with a real human head, a fake one, or some numerical model or something.
- TylerE 3y agoIt disagrees with me (2db) a lot less than it disagrees with you. (25db).
- kazinator 3y agoI have no idea what you're referring to; I have not given any estimate, only posited that it will be far short of the naive sum of 60 db. I have an even sneakier suspicion than before that you only read one sentence of my original comment, but don't let that stop you!
- Retric 3y agoThat’s likely due to sound conduction through your body. An isolated box inside another isolated box can reach well past +5db of improvement. This is how you can deal with truly extreme sounds like rocket launches and bomb tests. There’s some edge cases as distance doesn’t stack well with distance, but distance does stack well with ear protection.
- TylerE 3y agoThat’s my entire point! You have to consider the entire system and not isolated components.
- kazinator 3y agoOr, well, that's my point that you're trying to hijack as yours. Part of my point: that and that decibels do actually add, but you have to know the limitations.
- thghtihadanacct 3y agoThis sounds like an engineering student arguing with an old tech... 'but the science says ...'. How do people forget we live in an uncontained system with uncountable variables and no single direction?
- TylerE 3y agoThat's a very bad faith interpretation, especially considering your first post in this thread was...a reply to mine.
- aidenn0 3y agoMy reading of the comment that kazinator replied to was that the dB ratings don't add because of logarithms. Kazinator's reply was that logarithms add just fine, but flanking noise dominates.