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Natural Science Forum / Physics / Acoustics / September 2006Impact sound by raindrops
I am asking a question on impact sound by raindrops. We are proposing a small cafe area on a large podium. The walls and the ceiling will be constructed with thick glass panels. This idea is mainly due to artistic reasons. One of our concerns is impact sound due to raindrops !! We are afraid of a loud sound will be resulted inside the cafe area when heavy rain comes. Is there any international test standards or guidelines for accessing this potential sound problems ?? Methods in mind are to use "thicker glass panels" and "multiple layers of glass panels" with air space in between. Will these measures help ? Many thanks. Best regards, CSL >I am asking a question on impact sound by raindrops. > [quoted text clipped - 14 lines] >Best regards, >CSL A local restaurant has two conservatory areas; one has a glass roof and the other is corrugated plastic. In heavy rain the glass roof is essentially silent, while the plastic is deafening. d  SignaturePearce Consulting http://www.pearce.uk.com I do not know of any standard for measuring raindrop noise on a roof or evaluating roof constructions with regard to this. Some consultants have done some research on specific roof constructions for particular projects but I am not aware of any research on glass. Based on basic principles, either thicker glass or double layers or laminated glass would be better. As another poster indicated, plastics would be louder. Have you given any thought to how loud it is going to be inside just due to all the people talking in a space that is all hard surfaces. That would seem to be a constant and not just occasional concern. >I am asking a question on impact sound by raindrops. > [quoted text clipped - 14 lines] > Best regards, > CSL > I do not know of any standard for measuring raindrop noise on a roof > or evaluating roof constructions with regard to this. Some [quoted text clipped - 22 lines] >> layers of glass panels" with air space in between. Will these >> measures help ? Think about an automotive windshield, in rain. I don't think the impact of the raindrops is actually that big a deal, on normal glass. However, congratulations for thinking about it. For high frequency noise, thicker glass is probably the cheapest solution, but if the thermal properties of double glazing appeal to you, then that will be fine. Perhaps my perspective is warped, In my bit of Australia we like to hear rain on the roof. Cheers Greg Locock >I am asking a question on impact sound by raindrops. > [quoted text clipped - 14 lines] > Best regards, > CSL Have a look at http://www.bre.co.uk/filelibrary/IP02_06_Rain_noise.pdf#search=%22rain%20drops%2 0sound%20dB%22 Kari Pesonen Thanks to everybody for giving me hints to deal with this problem. I have read technical paper and the relevant test report. The information is helpful. We will consider glass roof panels, such as the "6-12-6" construction, mentioned in the report. Thanks again. Best regards, CSL "Kari Pesonen" <Kari.Pesonen@remove.welho.com> ¼¶¼g©ó¶l¥ó·s»D:efdr5b$5ls$1@nyytiset.pp.htv.fi... >>I am asking a question on impact sound by raindrops. >> [quoted text clipped - 18 lines] > > Kari Pesonen CSL, The BRE report should give you sufficient info on the rain noise issue, including a reference to the draft ISO standard. This is becoming more of an issue with the current architectural trend, at least here in the UK, for lots of glass and/or translucent products like polycarbonate and ETFE for building envelope construction. They look great but have lots of associated issued with not only acoustics, but also in terms of the structural, thermal and sustainable aspects. As Noral suggested, I'd be more concerned about effect on the reverberant noise levels of locating a cafe (lots of noise, people talking, clanking of plates, tables, chairs etc) inside a glass box. The end result may well be a very harsh, unpleasant sounding environment, where it is very difficult to even have a conversation across the table. I'd suggest you look at alternative finishes, which may be commercially available acoustically absorptive finishes (as a rule of thumb aim to cover an area equivalent to the ceiling area with a product of NRC 0.6 or more), or just simply lots of soft finishes. Depends on the asthetic you want for the finished space and how much money you have to spend. Regards Adrian > Thanks to everybody for giving me hints to deal with this problem. > [quoted text clipped - 29 lines] > > > > Kari Pesonen > As Noral suggested, I'd be more concerned about effect on the > reverberant noise levels of locating a cafe (lots of noise, people > talking, clanking of plates, tables, chairs etc) inside a glass box. > The end result may well be a very harsh, unpleasant sounding > environment, where it is very difficult to even have a conversation > across the table. you could use as sound absorbent transparent microperforated foil: http://www.microsorber.com/ that would allow you to combine transparency and good acoustics. I used this product on one project. It worked as expected. Expensive though... regards, Alain Bradette The CSR fire and acoustic design guide (called The Red Book) give a method of estimating the sound power level created by the rain. However I think that it is based on a sheet metal roof. Do a search for CSR acoustic design guide This should give you some estimate of the noise level then you can figure what sort of treatment to give to the roof Cheers, Tom > I am asking a question on impact sound by raindrops. > [quoted text clipped - 14 lines] > Best regards, > CSL |
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