trots Posted February 25, 2013 Share Posted February 25, 2013 Hi,I'm trying to find a solution to the bass from a 5kw PA system in a small geodesic dome causing irritation to some neighbors around 1km away. It's been stated in this thread that haybales will not help - but they seem to be the only cheap/available option for building large sound barriers. Are they of no use at all? Would they be more effective against bass if they were arranged into a double wall with an air gap inbetween? Any further advice anyone can provide would be much appreciated. Thanks! Link to comment Share on other sites More sharing options...
cfmonk Posted February 25, 2013 Share Posted February 25, 2013 Hi Trots, And for anybody else who reads this post, the only way to stop or reduce sound spill in a marquee effectively is with a "Sound Ceiling" My link. These are not cheap and I don't know of anybody who keeps them in rental stock and I doubt you will be able to hang them safely in a Geodesic dome...Solid ISO walls with padding, double glazing panels etc. will help but again, they're not cheap and you can't fit them to a dome. Hay bales may work but in their hundreds and in stacks 15m high. It's likely to ruin the look of your venue though... Link to comment Share on other sites More sharing options...
trots Posted February 25, 2013 Share Posted February 25, 2013 Thanks for the reply. Unfortunately we can't afford any expensive PA hires. We're not too worried about the external appearance aspects - the sound quality and level inside is our primary concern. Do you know (or does anyone else) if a 4metre high wall would have any impact on low frequencies? Thanks again Hi Trots, And for anybody else who reads this post, the only way to stop or reduce sound spill in a marquee effectively is with a "Sound Ceiling" My link. These are not cheap and I don't know of anybody who keeps them in rental stock and I doubt you will be able to hang them safely in a Geodesic dome...Solid ISO walls with padding, double glazing panels etc. will help but again, they're not cheap and you can't fit them to a dome. Hay bales may work but in their hundreds and in stacks 15m high. It's likely to ruin the look of your venue though... Link to comment Share on other sites More sharing options...
Ynot Posted February 25, 2013 Share Posted February 25, 2013 The problem is a we have had one previous 18th birthday party in a marquee (In 2007) and the sound spill was awful. Especially the bass. It somehow sounds 10x louder outside than inside. Here's a radical solution to part of that issue.... TURN THE BLOODY BASS DOWN!Even a couple of notches will help. Seriously, whilst I do like a nice bassy beat, and always have done since my formative years, I often despair at the seemingly inane 'need' for modern playlists to have often nothing BUT the thump-whump-thump of overbearing LF. ake SOME of that waway and in the emperor's-new-clothes sort of way I'd bet half your punters or more won't notice...!! Link to comment Share on other sites More sharing options...
Brian Posted February 25, 2013 Share Posted February 25, 2013 Do you know (or does anyone else) if a 4metre high wall would have any impact on low frequencies?To work it out accurately you'd need a lot more information but, with the following assumptions... 1) Speakers at ground level2) Listener at 1m above ground level3) Wall 4m high4) Wall 20m from speakers5) Listener 1000m from speakers6) Ground *completely* flat ...you can calculate a reduction at 125Hz of 7.8dB (ignoring curvature of the earth!). This would drop to 3.9dB at 63Hz. Link to comment Share on other sites More sharing options...
kerry davies Posted February 25, 2013 Share Posted February 25, 2013 A little more info would be useful, such as how big is the dome, what skin has it got, what is the configuration of the system and what sort of dB is it chucking out at the tent walls. If it is a real "Geodome" then let me know details and I will check with the designer/builder but I have a suspicion you are trying to fit quarts into pint pots. Domes are great for sound and if your neighbours are complaining 1000 metres away it is possibly just too loud. Link to comment Share on other sites More sharing options...
trots Posted February 25, 2013 Share Posted February 25, 2013 Thanks for working that out - that's really useful. Would you please be able to provide me with the formula you used so that I can play around with the different variables? Do you know (or does anyone else) if a 4metre high wall would have any impact on low frequencies?To work it out accurately you'd need a lot more information but, with the following assumptions... 1) Speakers at ground level2) Listener at 1m above ground level3) Wall 4m high4) Wall 20m from speakers5) Listener 1000m from speakers6) Ground *completely* flat ...you can calculate a reduction at 125Hz of 7.8dB (ignoring curvature of the earth!). This would drop to 3.9dB at 63Hz. I haven't got the spec at the mo - I'm just waiting to hear back from the provider. Glad to hear that they are great for sound, and we don't want it to be deafening - I'm just trying to find ways to avoid the potential for any noise complaints where possible. Thanks both! A little more info would be useful, such as how big is the dome, what skin has it got, what is the configuration of the system and what sort of dB is it chucking out at the tent walls. If it is a real "Geodome" then let me know details and I will check with the designer/builder but I have a suspicion you are trying to fit quarts into pint pots. Domes are great for sound and if your neighbours are complaining 1000 metres away it is possibly just too loud. Link to comment Share on other sites More sharing options...
dbuckley Posted February 25, 2013 Share Posted February 25, 2013 We've got farmers fields all over the place here with walls of hay bales several metres tall, and I always assumed they had these walls of hay for animal feed. How naive I've been: these guys are all obviously partying late into the night with big sound systems. Also explains why I see a lot of Aggrekos on the move too... Things you learn from the Blue Room! Link to comment Share on other sites More sharing options...
Simon Lewis Posted February 25, 2013 Share Posted February 25, 2013 Trying to stop noise after it has left the tent is somewhat hard work. It's better to reduce noise at source - either by turning it down, by using directional LF techniques, by careful positioning and by barriers close to the source.For calculations, try looking for barrier + attenuation. Sites like this one are helpful. Link to comment Share on other sites More sharing options...
LXbydesign Posted February 25, 2013 Share Posted February 25, 2013 This may sound ridiuclous and Im in no way an accoustic engineer - but I came across a home cinema system where the subs are mounted on plates and stand on 'spikes'. I belived it solved the problem of reducing the bottom end from being absorbed and distributed around the property thus being more 'airborne' which was then easier to control. Would or could this not be applied in the same instance? Ok so the mid and tops are rigged higher up and the sound is then absorbed into the crowd. The noise is not being absorbed through the ground and being carried is it ? Would the same principal not work for the subs ? Link to comment Share on other sites More sharing options...
Simon Lewis Posted February 25, 2013 Share Posted February 25, 2013 This may sound ridiuclous and Im in no way an accoustic engineer - but I came across a home cinema system where the subs are mounted on plates and stand on 'spikes'.Nice idea, but not really the answer in the OP's case, unless he is generating sufficient ground borne vibration to be heard and felt 1km away (quite unlikely). The reason it works indoors is that vibration can be quite effectively coupled through floorboards, underfloor cavities etc., so minimising the contact area that the cabinet has with the floor (or decoupling it with the right type of rubber or foam) can help stop this transmission. Outdoors, although vibration can travel through the ground, usually something bigger and heavier is needed to make ground borne vibration problematic. Like a train, or quarry blasting... Link to comment Share on other sites More sharing options...
J Pearce Posted February 25, 2013 Share Posted February 25, 2013 It might me interesting to note that a not dissimilar technique is used to cut transmission of noise from inner city tram lines.As others have said I doubt it would have much impact outdoors, soil and grass/scrub tend to be reasonable absorption materials. It might have an effect if the subs and the building were both on the same concrete plate. Outdoors noise control gets very complex and it is just much easier to not create the noise than it is to stop it. Directional speakers, lower SPL, distributed systems, careful pointing, and good management will all make a bigger difference than hay bales. Link to comment Share on other sites More sharing options...
adam2 Posted February 26, 2013 Share Posted February 26, 2013 There is no cheap or simple answer.Hay or straw bales help to an extent, but you need a lot of them, remembering that the sound leaks round the edge of the wall of bales, you will need a wall a lot higher and wider than the source of the sound. Lightweight materials work to a limited extent especialy if two layers of different materials are used with a significant gap in between.I achieved fair results with a wall of wattle fenceing, a gap of 2 M and another wall of Heras fence panels covered in heavy sacking. Link to comment Share on other sites More sharing options...
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