Sabines

Hello all ! I am very curious about this, i found somewhere a caution about not confusing between Imperial and Metric Sabines I understand that 1 sabine in Imperial system represent the absorbtion coefficient of 1 square foot of a given material, but what if you have imperial sabine coefficient and want to translate them in Metric Sabines (for 1 square meter) ? Do i multiply by 10,76 (1 sq/m = 10,76 sq/feet) ? This sound inappropriate to me (0,99 s imp would give more than 10 s metric !) Help me !!!! Philippe

The Sabine is defined as a "black hole" 1 foot square - in other words, it's the equal of a 1 square foot hole in the wall where NOTHING comes back. So the metric equivalent ( I didn't know there WAS a metric equivalent) would seem to be as you stated, or roughly 10.75 TIMES as much absorption (at whatever frequency is being measured) as the Sabine - maybe if Eric is around he can clarify whether there's a European/metric version, and whether I'm full of the proverbial doo-doo :roll: Steve

Sorry i already had people answering that question on studiotips (including eric !) BTW this is not what you say at all i did answer to these kind people this way: Thank you all for helping ! Correct me if i am wrong: you have an absorbtion coefficient like let's say 0,01 (noted a), if you have 100 sq/ft you will get 1 Imperial sabine (noted 1 Sa), and if you have 100 sq/m you will get 1 Metric sabine (noted 1 Sa) but used in a different formula as the TR 60 metric formula is not the same as the Imperial one. Is that OK ? Eric's answer: Yes you're right. The US Sabine formula T=0.049(V/A) The Metric one: T = 0.161 (V/A) http://www.diracdelta.co.uk/science/sou ... ource.html You find this Metric one from 0.16 to 0.163. This is related with temperature, speed of sound etc. (the 0.16 is not related with temperature and speed of sound but relates more to simplification by rounding) The 0.161 is a good one, representing standard room temperature. FWIW thank you for taking the time Philippe

Sabines are not coefficients, they are absolutes - coefficients assume a RATIO. A one square meter hole would still absorb everything that hits it - a one square meter concrete wall 10 meters thick would still REFLECT everything that hits it. Having nine square meters of concrete and one square meter of "black hole" would = an absorption coefficient of 0.10, as would having a 1 square FOOT hole surrounded by 9 square FEET of concrete. Eric's comments are correct as usual - but be careful not to confuse coefficients of absorption with absolute units... Steve

Philippe and Steve, Philippe, if you crosspost the same question it's gentle that you enter the link to the other thread or group. This causes people trying to help, having no idea what is discussed already about this. Asking a second opinion, if you're unsure is something different than entering identical requests on multiple spots. The Studiotips thread: http://forum.studiotips.com/viewtopic.p ... a38883cb9d Steve, Here was a discussion with a European acoustician (relative recent on the net I assume), not familiar with ASTM notions, who was really confused by it. It can be interesting to see my related reply (link included in studiotips thread): http://womb.mixerman.net/showpost.php?p ... stcount=23 Indeed sabins is a typical ASTM notion, which you will not find in our standards or a lot of acoustic study books. When I came on the net (around 2000 if recalling correct), I heard of it, but was not familiar with the use of the notion/unit 'sabins' either, while doing acoustics far over 20 years already back then. I really had to check to make sure I used it for our correct alternative (just a matter of knowing which is which of course). :) I think the reason, one isn't often confronted with this confusion by ISO notions is that most European people frequenting these groups, have no or little theoretical background in acoustics, therefore can't be confused (it's all new to them), just taking over the US approach from the net. If these same European guys discuss their collected knowledge with a local acoustician, not familiar with the net, it's quite possible a comparable confusing discussion establishes as in the above linked thread. We use the notion A for equivalent absorption. Now the fun part is that in the ASTM standards our ISO notions are integrated, since the official acoustic US language is SI and metric. Hence your standards include both alternatives. Only for convinience, the imperial alternatives are also integrated in the standards. That link explains the relation between both in more detail.

Eric, as usual I can't read one of your posts without learning something - thanks, and I hope you're doing well these days... Steve

Phil, Be sure to read the entire thread over at the Womb to see how confusing this stuff can seem, and how "passionate" some people get over sabins. :) Here's the link: http://womb.mixerman.net/showthread.php?t=3090 --Ethan