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<blockquote data-quote="Brad Weber" data-source="post: 40392" data-attributes="member: 114"><p>Re: Acoustic treatment alternatives</p><p></p><p></p><p>Greg, that looks like the Sonotube approach to diffusion, and in some cases bass traps, that some people promote. The biggest concern I have is that I have yet to see information showing that Sonotube (or whatever material they use) is appropriate for such use in public assembly spaces in terms of the Flame Spread and Smoke Developed ratings. Some people recommend simply covering the Sonotube with a fire rated material but the 'tubes' would seem to need to be closed at both ends and have all exposed surfaces covered with a properly rated finish.</p><p></p><p></p><p>As JR noted, there seem to be many materials that could fit the description "eco insulation" and not only board type materials as those Caleb linked or batt insulation such as <a href="http://www.ecobatt.us/" target="_blank">http://www.ecobatt.us/</a> but also spray-on foams, injected foams, blown-in cellulose and so on.</p><p></p><p>At least in my experience, the fabric is often a greater portion of the cost than the core material. There are probably numerous less expensive options than Guilford of Maine FR701 for the fabric, although for many you may be guessing as to the effectiveness in an acoustical panel application unless you can get samples to assess. And make sure that whatever you use has the appropriate Flame Spread and Smoke Developed ratings for the space.</p><p></p><p>I understand just wanting to 'deaden down' the space but being significantly more 'dead' at some frequencies than others can have its own issues. If you look at the absorption data presented in <a href="http://www.bondedlogic.com/construction-products/acoustical-panels" target="_blank">http://www.bondedlogic.com/construction-products/acoustical-panels</a>, you see that with the 1" panels you might get a lot of absorption at 1kHz and even 500Hz, but much less at lower frequencies which can lead to the room being 'boomy'. Also keep in mind that you can often get diminishing returns. Say you have some absorption in a room and add additional absorption to get twice the amount total absorption. To get that same change again requires going from twice the original value to four times that original absorption, which requires adding much more absorptive material than for the first step. When you combine these, unless there is some other factors to be considered then it is often more cost effective to treat the surface areas that will provide the most effectiveness first and see where that puts you rather than covering everything from the start.</p><p></p><p>By the way, ignore the absorption coefficients that are greater than 1.0 in the insulation product data as that is an anomaly of the testing method and how the samples are prepared and arranged. A 2" thick, 2' x 2' panel has an edge area of 1.33 square feet, so whether that edge is exposed, butted up against another panel, surrounded by a wood or metal frame, etc. can make a difference in the amount of total material exposed to the room for the same face area. Smaller, spaced samples versus one, large contiguous sample and other factors can also affect the results of lab absorption coefficient tests with the result that you can get values greater than 1 when that is not really physically possible. Of course, few real world rooms have true reverberant fields anyways so how well the absorption coefficient test values relate to real world performance is also imperfect, especially as the direction from a sound source approach grazing angles to the absorption material face.</p></blockquote><p></p>
[QUOTE="Brad Weber, post: 40392, member: 114"] Re: Acoustic treatment alternatives Greg, that looks like the Sonotube approach to diffusion, and in some cases bass traps, that some people promote. The biggest concern I have is that I have yet to see information showing that Sonotube (or whatever material they use) is appropriate for such use in public assembly spaces in terms of the Flame Spread and Smoke Developed ratings. Some people recommend simply covering the Sonotube with a fire rated material but the 'tubes' would seem to need to be closed at both ends and have all exposed surfaces covered with a properly rated finish. As JR noted, there seem to be many materials that could fit the description "eco insulation" and not only board type materials as those Caleb linked or batt insulation such as [url]http://www.ecobatt.us/[/url] but also spray-on foams, injected foams, blown-in cellulose and so on. At least in my experience, the fabric is often a greater portion of the cost than the core material. There are probably numerous less expensive options than Guilford of Maine FR701 for the fabric, although for many you may be guessing as to the effectiveness in an acoustical panel application unless you can get samples to assess. And make sure that whatever you use has the appropriate Flame Spread and Smoke Developed ratings for the space. I understand just wanting to 'deaden down' the space but being significantly more 'dead' at some frequencies than others can have its own issues. If you look at the absorption data presented in [url]http://www.bondedlogic.com/construction-products/acoustical-panels[/url], you see that with the 1" panels you might get a lot of absorption at 1kHz and even 500Hz, but much less at lower frequencies which can lead to the room being 'boomy'. Also keep in mind that you can often get diminishing returns. Say you have some absorption in a room and add additional absorption to get twice the amount total absorption. To get that same change again requires going from twice the original value to four times that original absorption, which requires adding much more absorptive material than for the first step. When you combine these, unless there is some other factors to be considered then it is often more cost effective to treat the surface areas that will provide the most effectiveness first and see where that puts you rather than covering everything from the start. By the way, ignore the absorption coefficients that are greater than 1.0 in the insulation product data as that is an anomaly of the testing method and how the samples are prepared and arranged. A 2" thick, 2' x 2' panel has an edge area of 1.33 square feet, so whether that edge is exposed, butted up against another panel, surrounded by a wood or metal frame, etc. can make a difference in the amount of total material exposed to the room for the same face area. Smaller, spaced samples versus one, large contiguous sample and other factors can also affect the results of lab absorption coefficient tests with the result that you can get values greater than 1 when that is not really physically possible. Of course, few real world rooms have true reverberant fields anyways so how well the absorption coefficient test values relate to real world performance is also imperfect, especially as the direction from a sound source approach grazing angles to the absorption material face. [/QUOTE]
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