many times and accepted theory for insulation density. For some reason the last time I read it the paragraph stood out to me regarding recording studios.
(boldface by me)
Comparative listening tests on the receiving side of test partitions emphasized the importance of isolating the upper frequencies when the source is music, If high-frequency isolation is substantially out of balance with mid-frequency isolation, the mid-frequency harmonics can be heard, along with the high-frequency fundamentals, as an unnatural (telephone quality), highly intelligible sound. However, if the partition can attenuate the sound so that the intrusive music sounds natural and unfiltered (similar to a stereo played at low volume), the intrusion is not nearly as objectionable. This result can be created by a partition with a sound transmission loss curve that, starting at about 31 Hz, rises at a nominal rate of about 12 dB per octave to 400 or 500 Hz, gradually flattens out in the next octave and then remains relatively flat above 1,000 Hz. Except for special facilities such as recording studios and music buildings, it is seldom economically feasible to totally isolate loud music, especially when the background noise level is very low in the adjacent spaces. Therefore, a partition with these general characteristics is the best choice when isolating music. Insulation density is an important resource to use in achieving this goal.
My take now is that if you are trying to make the studio inaudible to other spaces, then the 2.5 lb/ft^3 criteria is moot. What should become significant is price and availability of product. As things work out, the 2.5 lb/ft^3 material is usually among the most economical and available, due to the popularity of SAFB type insulation. However the mantra for studio construction is not as all encompassing as it first reads, or the first 67 reads either.
I hope this helps confuse an issue where we thought we had at least one clear guideline.
Me too - if I recall, that was an excerpt from an original document; I don't remember whether there was an option to purchase the original or not Steve
Andre maybe I'm looking at some thing different. But I don't think they are saying 2.5 lb/ft^3 criteria is moot.
The 2.5 lb/cu.ft. insulation provides better results when isolating either speech or music and provides a distinct advantage in minimizing the negative effects of the sound leaks associated with electrical outlets.
I believe they are saying economincally it's not practical to build a structure using these materials (i.e. go for the cheapest price). Unless you are building a studio or such.
Except for special facilities such as recording studios and music buildings, it is seldom economically feasible to totally isolate loud music
Since we are trying to build studios doesn't 2.5 lb/ft^3 still make the most sense?
Steve