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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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      CommentAuthorfostertom
    • CommentTimeJan 8th 2021
     
    I thought I understood this, but am finding it difficult to get advice on building design principles to prevent noisy (airborne and impacts) activities (e.g. music, drama workshop) within from breaking out to affect neighbours. All search results assume it's about protecting from incoming neighbour noise, or reducing noise between rooms etc.

    My gut says my building should be airtight including ducts outlets etc, massive walls, roofs and doors, thick windows glass. I've never been sure about noise absorbent materials lining the walls - doesn't that just capture more noise energy into the walls, for onward (outward) transmission?

    An alternative principle might be to isolate the interior lining from the exterior weatherproof skin, with absobency between to killl pressure waves transmitting across the void.

    My gut also says straw bales, perhaps double thickness of, would be ideal - both fairly heavy and absorbent in depth, provided they can be made airtight.
    • CommentAuthorowlman
    • CommentTimeJan 8th 2021
     
    <blockquote><cite>Posted By: fostertom</cite>

    "An alternative principle might be to isolate the interior lining from the exterior weatherproof skin, with absobency between to killl pressure waves transmitting across the void."


    I guess some sort of cavity construction, maybe a bit wider than usual, with rockwool batts between would do that fairly well....No?
    • CommentAuthorLF
    • CommentTimeJan 8th 2021
     
    Had some experience on noise on industrial equipment.
    Air gaps are key. 10% free space means that a wall may as well not be there
    Need some soft stuff in a room to stop reverberation - this can amplify by 6 dB which is a lot.
    High frequency noise is easier to stop than low frequency - you need a frequency spectrum for what you are trying to stop.
    I remember 1 project where a steal frame building way done by the mechy engers. It had perforations on inside. Then plasterboard. Then air gaps then rockwool then steel sheet on the outside. The air gap helps to attenuate the noise. Think car exhausts. But you need to know frequency and wavelength you are targeting

    We also did a extension on side of house and put wooden floors upstairs for kids room. Stuffed void with rockwool - heavy spec and it did very little to stop noise - disaster. Heavy underlay and carpet were needed.

    I think you need isolation parts that stop noise directly transmitting.

    Sounds like you could loose a lot of money specifying something and getting it wrong !
    • CommentAuthortony
    • CommentTimeJan 8th 2021
     
    I used two dg units in frames with 200mm space non opening for windows, dense concrete blocks, can’t hear music group outside
    • CommentAuthorSimonD
    • CommentTimeJan 8th 2021 edited
     
    Once upon a time I used to design exhaust systems for racing motorbikes so have had to deal with this problem so as not to completely p*$s off my neighbours!

    This is a rather complicated business.

    As your gut suggests density, thickness and airtightness are your friends but the design does depend on the amplitude and frequency of the sound you're having to deal with as well as the room design - because the room itself may resonate and thus amplify certain problematic sounds in a rather unhelpful way!

    Ideally you need to reduce door and window area as much as possible.

    I'd reckon straw bale, rammed earth, subterranean or perhaps thick icf (possibly not that green) would be fairly good starting points but see below re Celenit.

    With my stuff I solved the problem by first understanding the frequency profile of sounds I was dealing with and then employing a mixture of mass (dense concrete blocks), absorption and resonance (building some resonators specific to the worst frequencies) according to the dimensions and acoustic properties of the garage. I bought a load of books on acoustics and then developed my own spreadsheet to model the sound.

    Posted By: fostertomI've never been sure about noise absorbent materials lining the walls - doesn't that just capture more noise energy into the walls, for onward (outward) transmission?



    No, the noise absorbant materials basically take the sound energy and turn it into heat, and they tend to be used to reduce resonance within the room, which may well reduce conduction through the walls (but dependent upon frequency).

    There are lots of products on the market for this but for house design, have you looked at suppliers of the wood wool boards such as Celenit as part of the solution?

    from Celenit's website regarding perimeter walls:

    "With regard to the sound insulation of the perimeter wall or roofs, the sound insulation index of the different elements composing the building must be evaluated, in particular the walls, roof, windows and doors, and then a calculation must be made that also takes the building geometry into account. CELENIT provides certified stratigraphy for perimeter walls and roofs, which guarantees excellent sound-insulating performance."
    •  
      CommentAuthordjh
    • CommentTimeJan 8th 2021 edited
     
    The lengths you go to depend entirely on what you're trying to achieve, and whether it's best efforts or contractual! In the latter case take professional advice :devil: I visited quite a few music studios a long time ago - they went to extremes. Air Studios' old place on Oxford Street was built as a separate structure within the existing building with rubber suspension underneath to support it. Utrecht Radio has 10-layer glazing because it's built overlooking a major roundabout. Some places have anechoic chambers.

    The basic ideas are (a) separate structures with no links, (b) lots of mass, flexibly mounted where possible, (c) absorbent materials between layers and to some extent on the surface. Obviously airtight.

    Impact noise goes straight through any structure, hence separate ceilings underneath structural floors etc, or resilient bars with lots of plasterboard on, separated from the structure at the edges. Same for walls; either two separate walls or resilient bars. Lots of mass in the layers - multiple layers of acoustic platerboard, mass vinyl layers etc. Absorbent stuff between layers - acoustic mineral wool etc.

    Surface treatment isn't so important from a simple measurement point of view, but can make quite a difference to how things sound in a room. Venezuelan cork was all the rage that long time ago. Heavy curtains are sometimes used. There are proprietary products with lots of holes in the front that supposedly damp noise.

    Impact noise - separate structure. High frequencies - surface treatment can help.

    edit: oh and yes straw bales with lime rendered skins work quite well, thanks :bigsmile:
    • CommentAuthorBeau
    • CommentTimeJan 8th 2021
     
    Did a bit of work on an industrial site to contain the noise of a massive planer. Basically, the box was the size of a small house. It had to be light and movable so we went for a timber frame with HD Rockwool infill. Tested at this stage and it was brilliant even when open on the end. Sadly due to dust and potential fire hazard it had to be lined so we used resilient stip and HD plasterboard. It was nothing like as good once lined but brought the DB down enough to comply with their license. The absorption of the Rockwool exposed to the noise was remarkable working much like an anechoic chamber. Gut feeling is your straw bale plan would be good.
  1.  
    I think you need a different approach depending on whether you are trying to deaden all noise, or simply noise audible from outside the house. As it's music etc I presume you actually want the full frequency range and volume inside?
    I remember once being inside the anacoustic chamber at the Building Research Station. There was zero reverberation inside because of the acoustic padding, and it was really difficult to hold conversations etc. All sound was sort of whipped from ones's mouth and stifled. Music would have been unplayable.
    One forgets how important the right degree of echo is in the appreciation of sound and ambiance - ask a blind person.
    •  
      CommentAuthorfostertom
    • CommentTime4 days ago edited
     
    Thanks v much guys - really good experience and suggestions. Unfortunately the project has slipped away, when I told them how much it would all cost! But I have the info filed away for next time. Thanks again.

    Posted By: Beauwe used resilient stip and HD plasterboard
    Beau, I wonder if it was the resilient strip that reduced the effectiveness? Its purpose is to isolate structure behind it from sound waves in the room. Maybe resilient strip, which allows the pbd to vibrate half-freely, maybe even reinforces the sound in the room, while in this case preventing (or halving?) the pressure waves that reach the Rockwool?
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