I'm new here and also new to sound isolation and acoustics really. Signed up to try and find somewhere a bit more friendly than gearslutz, so please don't be too harsh on me!
Have been doing all the reading I have had time for in the last week or so on sound insulation!So, there is this nice basement going for a really good price, and I have a nice business partner to share investment with me, and potentials interested in time-sharing with us. However I have concerns about the amount of sound insulation required and have been trying to find out if this amount is even possible, I think I am beginning to understand some important concepts, but I really could do with the voices of experience to help me out!
The problems are: a hair salon upstairs with I think pretty much only floorboards to seperate, I guess a layer of plasterboard too. And potentially two residences on either side (do not actually know this for certain yet, are waiting to find out who the horizontal neighbours actually are) seperated by brick walls (do not know if these are cavitied brick walls or not yet, we are trying to find out)
Now, I have been looking into construction methods and STC class ratings of common types of construction. So two wood or metal stud walls with 3 1/2" insulation in each, and double layers of drywall on each outer side seperated by something like green glue seem to have an STC of not much over 60. In fact on various sites, I have not heard a wall described of above 65 that is not a double concrete wall with a massive air gap etc. For the ceilings and walls I believe we probably have a maximum of 16-18" space to use up for sound insulation purposes. Is there even theoretically anyway to get STC values of higher than 65 with this amount of space?
The reason I worry if we need to achieve a higher STC than 65, is this following reasoning: If a drum kit can produce 120dB SPL in our live room, doesn't that mean we need to reduce about 80dB transmission to avoid noise complaints? 40dB to me sounds like a relatively safe target level of transmission, considering the hair salon play the radio, and we only make this transmission in daytimes to concern the horizontal neighbours? Is this a reasonable target of 40dB, or could we get away with a bit higher than this/or do we need to get lower still??
Is it correct that an STC of 65 would only reduce about 65dB average (and probably much less than this at lower frequencies?) Surely that won't really be enough if a drummer is producing 120dB?
Also is the only way to get a better reduction of the low frequencies to have tons of mass, quarter of the wavelength of the low frequency? I mean even if we build our ceiling to be 500mm thick that is only 154hz that that is a quarter wavelength of, there's a hell of a load of bass and kick drum below that!
Many thanks for your time
