Keeping Noise at Bay: Straw Bales As Soundproofing

cars in traffic Many of you have written to me in recent months asking about straw bales as soundproofing options against noisy streets and neighborhoods. I have responded to a lot of you individually, but figure it’s better to give everyone this information as well.

I have to start with a funny story. Last night, as I was trying to go to sleep, the outside gate was swinging and banging in the wind. The gate is attached directly to the side of the house we’re currently renting (no, it’s NOT straw bale, and thus the funny story). My wife was still awake and so I asked her if she could go outside and close the gate. She did and when she got there, I could hear she was having trouble getting it to latch. Without leaving my bed I said, “you have to lift the gate up and push it towards the house while you latch it.” She thanked me for the input, latched the gate and came inside. We both laughed when we realized we had just had a clear conversation, with no difficulty hearing each other, right through the wall of our house!

What a sorry state of affairs it is when we can actually talk through our walls. The walls are insulated, by the way, but even still, they are easy to talk through. That would never happen in a straw bale house, I guarantee it! In fact, when my crew would work on straighten walls, after they were all stacked, they would often use walkie talkies to communicate with the person on the other side of the wall. Without those, they would have to walk over to a window opening and reach their heads out to communicate with each other.

So the answer to the question is yes. Yes, straw bale buildings are incredible insulators from sound. If you live on a very loud street or perhaps you back to an interstate, these walls will eliminate almost all of the noise that you currently live with. You can build a straw bale house or consider building a straw bale landscape wall. Although not as good as an entire house of straw, they still work really well to eliminate sound.

The science is in the density. Sound travels as waves. When it moves through hard material, it travels in fast, short waves. When it travels in soft material, the wavelength increases and slows down. Now look at a straw bale wall. The outer plaster skin is hard and dense and so the sound waves move through it at high speeds; however, when they hit the bales, the sound waves slow down. The key here is the interior plaster. In order for the sound waves to escape the soft bales, they would have to accelerate to get into the hard plaster skin. They can’t do that and so end up absorbed in the bales. Voila, noise supression 101 and straw bales as soundproofing options work so well!

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39 Responses to Keeping Noise at Bay: Straw Bales As Soundproofing

  1. Mark Gibbs Mon, November 23, 2009 at 6:24 pm #

    Your explanation of sound insulation is incorrect … when it comes to sound, what matters is how much the energy of a sound wave is attenuated when passing through a material.

    From NDT (yes, this site concerns ultrasonics but the basics apply to everyday frequencies):
    “When sound travels through a medium, its intensity diminishes with distance. In idealized materials, sound pressure (signal amplitude) is only reduced by the spreading of the wave. Natural materials, however, all produce an effect which further weakens the sound. This further weakening results from scattering and absorption. Scattering is the reflection of the sound in directions other than its original direction of propagation. Absorption is the conversion of the sound energy to other forms of energy. The combined effect of scattering and absorption is called attenuation.”

    See also:

    http://www.britannica.com/EBchecked/topic/555255/sound/63976/Attenuation

    and

    http://asksciencelions.blogspot.com/2009/02/how-does-soundproofing-work.html

    Regards,
    Mark Gibbs.

  2. Andrew
    Andrew Mon, November 23, 2009 at 6:36 pm #

    Thanks for the correction and input Mark. I appreciate the feedback and references.

  3. Darold Heikens Wed, July 7, 2010 at 9:24 pm #

    Andrew, do you know if any strawbale soundwalls have been built within the transportation environment. I work as a Project Manager for the California Dept. of Transportation in Sacramento and would like to use strawbale for soundwalls but have problems convincing the engineers, also because they require them to be overbuilt so much the straw walls don’t have much if any savings given the risk in their mind. Examples would help me persuade.

  4. Andrew Morrison Sun, September 5, 2010 at 12:50 pm #

    Hi Darold. Sorry for the delay in getting back to you. I believe that sound walls were built along the highways of Nevada in some cases. I don’t know for sure, but this was a rumor some years ago. Please let me know what you find or if you want help convincing the engineers.

    Best of luck to you.

  5. Paul Herwin Thu, October 24, 2013 at 6:47 am #

    I have made extensive research into straw bale sound insulation and whilst they offer very good attenuation at high frequencies they are poor at insulating low frequency noise. The majority of straw bale houses built thus far have been detached and in rural areas where I suspect there are less problems with low frequency music and buses etc. In these conditions the straw bale walls do indeed feel like they are super insulators as the natural rural sounds, which tend to be in the mid and higfh range, are attenuated. With the advent of semi-detached and terraced straw bale houses it has been found that single bale walls do not meet the building regulations for sound in the UK and need extra partitions added to pass. Whilst density is a factor in sound insulation stifness is also as important and there is a need to stiffen straw bale walls to improve their performance at low frequency. Single panel walls rarely perform well at low frequency which is why the use of double layers with cavities are usually used for sound insulation (and thermal insulation).

    I have a collection of tests which show the poor performance and have also found that most of the literature quoted as proving the efficacy of straw as a sound insulator leads back to one or two tests with poor methodology and cheap, innacurate and uncalibrated equipment. Unfortunately, private building control firms in the UK continue to rely on these sources and buildings are passed as fit by local authority building control departments with no experience or knowledge of straw or it’s poor performance.

    I don’t wish to be negative as I love the idea of straw and would love to build in this way but my investigations now make me doubt the reliability of some of the other ‘scientific’ evidence which is presented for straw consruction.

    A paper of mine was presented in montreal this year on this subject: http://scitation.aip.org/content/asa/journal/poma/19/1/10.1121/1.4798962

  6. Andrew Morrison Tue, January 7, 2014 at 1:45 pm #

    Hi Paul. I would be interested to compare your studies with “in the field” living situations. Many of the homeowners that I know who live in bale homes report incredible soundproofing qualities, whether they be rural or urban locations. In fact, the City of Las Vegas used a few straw bale walls as sound barriers along their highways some years ago with success. I know of many homeowners who use straw bale landscape walls to quiet their properties along highways and busy streets.

    I’m not disagreeing with your findings; however, I have seen similar testing results in regards to Rvalue that don’t jive with real life experience. In fact, the stated Rvalue of a bale is very low when tested in the lab; however, people find day in and day out that their homes are easily saving them 75% on heating and cooling bills each month as compared to conventional homes. Why? Because the lab testing does not take into account the entire system and how it works in “real life.”

    I don’t know if you have similar feedback in terms of sound properties, but I can only speak from the feedback I have received from home owners as to how well the bales work for them.

  7. Nicholas Mintern, NZ Thu, January 16, 2014 at 9:10 pm #

    I am looking at building a straw bale noise barrier wall to block the noise of our next door boarding kennel from disturbing my neighbours and my family when they are outside. I also live in a straw bale house rendered with cob and can vouch, only from subjective experience, for the materials ability to attenuate sound at certain dog frequencies. As I live in a rural area and as dogs don’t bark very low in frequency, it isn’t a problem in my situation that the bales don’t absorb the low frequencies. Regulations aside, which frequencies truly matter when it comes to noise in a particular situation? What noise frequencies are present and most disturbing to the individuals in the situation where noise needs attenuation? Beware following regulations for the sake of regulations, I would advise to follow regulations as long as they make sense and are effective at serving the true purpose of the regulation. Looking at the graph in figure 5 of the above article “Straw bale sound insulation: Blowing away the chaff”, it appears to me that the bale walls perform very well at absorbing those frequencies 200Hz and above where the ear is more sensitive. It is of course important to attenuate the lower frequencies in many situations, though that can be fixed with stiff and heavy render right? I’d like to see direct comparisons of attenuation with frequency for other materials, especially the better performing ones. Where can I find such data? Thanks everyone for you contributions.

  8. Dale Wed, November 12, 2014 at 4:23 am #

    Hi andrew this article is brilliant exactly what I have been looking for. I was also wondering if you could somehow blend the straw down to a powder and then use adhesive to make it into a board for easy fixing to an existing structure as insulation and soundproofing? I am really challenged for space and am trying to keep it as effective and small as possible

  9. Andrew
    Andrew Wed, November 12, 2014 at 11:28 am #

    Hi Dale. Glad the article was helpful! There are straw board products available; however, I don’t know much about their r-value. I imagine it would not be very good because the vast majority of the r-value in a bale wall comes from the entrapped air inside the bales and the overall thickness of the walls. Removing that entrapped air and then thinning the layer would eliminate both of the vital properties.

  10. Dale Tue, November 25, 2014 at 4:49 am #

    Cheers Andrew. Thats a great help. Your the salt of the earth

  11. Johan Mánnel Thu, March 5, 2015 at 1:15 am #

    Hi Straw-bale builders,

    Iam currently about to write a dissertation about building with straw-bales

    Iam therefore interested in the sound insulation values of straw-bales in fx. (Rw) I imagine there must be a table indicating density and the measured sound insulation values.?

    And in general i’m interested in research made regards to Fire, Load Bearing capacity, Insulation, indoor climate – and of course the answer to a question i hear alot. “What do you do when rodents move in to your straw-bale wall and start nesting?”

    I have made some research and got some answers – But i could use some good references?

    Best regards/Johan

  12. savannah Sun, April 19, 2015 at 9:32 am #

    My situation is totally different. I am living next door to a rental used as a greenhouse-if you get my drift. The noise from constant a/c’s going 24/7 in all kinds of weather is deafening. When temps drop to below freezing those a/c’s whine and squeal so loudly. Not to mention the hiss from an air filter. All hitting my all too close side yard which magnifies the machinery sound and drives me CRAZY. Being in an HOA protected subdivision I thought I could get help there. Nada. I went to code enforcement, they came out during the day and said it is slightly above code in decibals, but I said it is WORSE at night, they don’t work at night, won’t do readings at night. Basically told me, nothing they could do. Although zoning says it violates “intended use” no one wants to enforce anything because of “who” rents the home, ugh.

    I wanted to try straw bale gardening this spring, went and got bales, put them against the shared fence, right across from the offending a/c, until I could clear the space they will go my the backyard. This is a commercial sized a/c used on a 1200 sq ft home, so it is a BIG BOY unit. Last night was the 1st night I barely heard the drone of the mchs-why, the straw bales absorbed the noise. It was heavenly NOT to hear the thing kick on and off in my bedroom. Who knew…I was told the only thing I could probably due was add drywall in my house, or spring for mass vinyl sheeting and attach it to the fence. Straw bales aren’t expensive and they absorbed the noise. So WOOOOOOHOOOOOO…I think I found a do-able solution.

  13. Andrew Morrison
    Andrew Morrison Sun, June 7, 2015 at 9:50 am #

    Indeed. You can make a permanent landscape wall that will look beautiful and absorb the noise that bothers you. Win-Win!

  14. Jeinny Sat, August 6, 2016 at 5:36 pm #

    I found this test info. http://acoustics.org/pressroom/httpdocs/130th/lay03.html

  15. clint fisher Thu, September 1, 2016 at 3:09 pm #

    Hi there, Im looking at building a 3m high 140m long straw bale outside wall, to attenuate traffic noise. Does anyone know where i might find any information how best to construct this beast. everything I’ve read only speaks about house walls or low 1m garden walls. Thank you.

  16. clint fisher Sat, September 3, 2016 at 2:42 am #

    Hi there, Just found the answer to this question on another section of this amazing site. Theres more questions on that thread though. Cheers.

  17. Andrew Morrison
    Andrew Morrison Mon, September 5, 2016 at 11:15 am #

    I responded to you on the other post; however, I want to publish this comment as well in case others on the site have information to share with you. Good luck.

  18. Chris McClellan Fri, December 2, 2016 at 4:10 pm #

    Hello again Andrew. You have your muddy paws in so many wonderful pots. I am looking at putting a little sound proofing in an interior wall so my wife and I an chat late at night or watch a movie without keeping the kids awake. I’m thinking straw clay and pallets, possibly plastered. Between 3 and 5″ thick. I wondered if you had any sense of whether a heavier more cobby straw clay or a lighter straw clay would be better. I hesitate to go too (heat) insulative because the room is on the north side with lots of east facing glass and the house is heated with a rocket heater a ways away. Thanks. And thanks on the work on tiny house code. –Uncle Mud (aka Chris McClellan)

  19. Andrew Morrison
    Andrew Morrison Fri, December 2, 2016 at 6:28 pm #

    Hi Chris. Great to hear from you. I would think that the lighter the mix, the better the sound attenuation will be. If the material is heavier, it’s going to have more mass, which means more sound transfer. The higher mass would be nice as thermal storage, but not so great for sound. On the other hand, the lighter mix will be good for sound insulation, but won’t provide much thermal mass. Hope that helps. Be well my friend.

  20. Mathew hughes Fri, December 30, 2016 at 8:57 am #

    Hi Andrew, I’m looking to try and build a rehearsal room/studio at the bottom of our garden, we live in a detached house but we have adjoining gardens, we’re hoping to use the space for personal music projects but also to rent it out, we need really good sound insulation as we do have houses fairly close by, do you think that bales would be sufficient? Many thanks mat.

  21. Andrew Morrison
    Andrew Morrison Fri, January 6, 2017 at 5:50 pm #

    Absolutely. Bale homes are incredibly sound proof.

  22. Sandy Vissman Wed, January 25, 2017 at 4:21 pm #

    Hi Andrew,

    Straw bales are being considered for shielding birds from noise, light, and disturbance associated with a road expansion. Do you have any contacts or papers regarding the use of straw bales in such a setting? I do not know the frequencies of the roadway equipment, but am trying to find out to see if this is a potential solution. There is also some concern about rodents, corvids, and other wildlife use of exposed hay bales. Do you have any info on this?

    Thanks! Learning alot on your site!

    Sandy

  23. Rosie Thu, February 16, 2017 at 4:45 am #

    I would like to build a sound proof boundary wall, specifically to reduce traffic noise. Our house is situated on a hill above a busy road, and so there is no sound barrier at all in the garden. I wanted it to look natural. Could you recommend any straw bale builders/ suppliers in the Surrey or London area UK? Does this need planning permission?

  24. Andrew Morrison
    Andrew Morrison Mon, March 6, 2017 at 8:56 am #

    Hi Rosie. Thanks for your message. I don’t have any builders that I can recommend in that area. You may want to look into whether Barbara Jones is still active via “Amazon Nails”. She is in the UK somewhere and may be able to help or provide a solid lead. In terms of council permission, that will depend on the size of the wall and the location. That is better answered by the planning board.

  25. Andrew Morrison
    Andrew Morrison Mon, March 6, 2017 at 9:05 am #

    Hi Sandy. Exposed hay bales would not be a good idea. They will be a food source and will rot with exposure to the weather over time. You can build a quality “garden wall” with straw bales, but the wall must be built to protect the bales from exposure. Plaster, a wall top device (roof or other protection, must be included in the design as well as a lift off of the ground to prevent moisture from wicking up into the straw.

  26. Louise Mon, July 3, 2017 at 6:05 pm #

    My son has recently converted the workshop shed into his music studio, so a lot of heavy base sound amplifies up to the neighbours property and mine. We are on five acres and the shed is approximately 50 meters from the house and 150 meters from the neighbours. We have put acoustic foam in sections of the shed to try to trap the sound inside, foam on the Windows, carpet on floor and insulation under the tin roof. The neighbour came over again last night to complain.
    After reading all the information regarding straw bails I was wondering if placing straw bails on only one of the outside walls of the covered verandah facing the neighbours would help?

  27. Andrew Morrison
    Andrew Morrison Mon, July 3, 2017 at 9:32 pm #

    Hi Louise. It very well could help attenuate the sound. Bales do an amazing job at that. On the other hand, it would be much better to do the whole house if you can. If that’s not an option, then I would definitely recommend the one wall. You can even do a sound wall away from the building too. The closer to the building, the better the results (with an actual wall wrap being the best. Good luck!

  28. Mick Sun, January 7, 2018 at 8:48 pm #

    Hi Andrew,

    Tried sending you a message yesterday but just wondering if sugar cane mulch bales would work as well for sound proofing

    Reg Mick

  29. Andrew Morrison
    Andrew Morrison Mon, January 8, 2018 at 10:13 am #

    Hi Reg. I have never used sugar cane baes as they are very coarse and I imagine would be difficult to resize on site (something that’s pretty much always required when building with bales). That said, I expect they would also do a great job of sound dampening.

  30. Mick Mon, January 8, 2018 at 4:37 pm #

    Thanks Andrew and thanks for the prompt reply greatly appreciated,,

  31. Andrew Morrison
    Andrew Morrison Mon, January 8, 2018 at 4:52 pm #

    You’re welcome!

  32. John Fri, March 16, 2018 at 2:05 am #

    Hi, Andrew I enjoy reading your site.

    I have a metal (double car size) shed that pings, rattles and hums with the slightest provocation and would like to play music pretty LOUD without the room having a party. Strawbale does sound like a pretty efficient sound absorber and am considering lining the interior, stacking them inside packed firmly and strapping them in place against the walls, thus trying to achieve “damping” the walls by restricting their movement while making the shed pretty soundproof.

    If the shed didn’t ping so much and the sound was contained that would do a pretty neat job of the old shed. I am pretty confident that makes sense.

    I’m going to fill the gaps, holes, and vents in the shed with foam to prevent water from getting in – the floor is already concrete and I’m going to build a wooden floor.

    That leaves the strawbales naked – I will be inside a strawbale room. What do I need to do to finish. Since they will not be subject to the weather can I just leave them bare? Will they smell or are they pleasant? Do I need to apply a protective render or will they simply rot if not sealed away from air?

    Hoping you can set me straight.
    John

  33. Andrew Morrison
    Andrew Morrison Fri, May 25, 2018 at 2:20 pm #

    Hi John. It’s always a best practice to cover the bales as unfinished straw can be susceptible to bugs, moisture and even mice. Lime plaster will make the bales sound a bit tinny on their own because it is so firm, so you may want to consider clay plaster. You might also want to angle the walls away from each other a bit (if possible) to help attenuate the sound vibrations. Finally, you will want to leave a gap between the metal shed and the bales (1-2″) so that the bales don’t rot from trapped moisture and/or condensation. The back side of the bales (facing the metal) should be dipped in plaster before placed (nothing fancy) to keep the risk of flame spread down. It’s possible to do this well and relatively inexpensively. Good luck.

  34. Kathy Winters Sat, June 23, 2018 at 5:54 am #

    Hello. I am building a round bale wall outside to lessen traffic noise. I live on a farm and do not plan to cover the hay. My thought is as it rots, I can plant on it and it will look more like a natural berm.
    It will be quite close to the road and I am hoping it will absorb much of the tire noise.
    Am I on the right track here? Thx

  35. Andrew Morrison
    Andrew Morrison Mon, July 2, 2018 at 8:04 am #

    i Kathy. That’s a very different approach than what I’m used to as I deal in finished homes, etc. That said, if your intention is to create a berm feel, this could be a good way to start. You’ll want to minimize the height as your plan to let it rot in pace will cause it to slump over time. If it’s too tall, it could become top heavy and fall onto someone. That would be bad as the bales, especially when rotting and wet, are very heavy. If it were me, I’d either commit to the berm and bring in some machinery to create it, or I’d build a landscape wall and protect for years to come. That’s just me though.

  36. Paul Herwin Wed, August 8, 2018 at 12:46 am #

    Hi Andrew,

    sorry to take so long to get back to you. The main personal impetus for my study was to see whether the requirements for sound insulation under the UK building regulations could be met. I understand many owners feel they are super soundproof, rural or otherwise. Self-builder/owners are more likely to ‘WANT’ to feel the thing they have built is doing what they think it is though! Straw bale thermal efficiency is definitely excellent. I have also been inside several straw bale houses and can attest that high and mid frequency noise is well attenuated, high frequency extremely so.

    Unfortunately the low frequency performance, as my tests and review of others’ tests showed, is quite poor. As most straw bale houses to date have been detached properties, often far from rumbling roads, this is not necessarily a problem. In regards to UK building regulations there is no compliance test for the sound insulation of a detached property other than sometimes the need to show the internal sound levels will be acceptable. The internal sound level criteria in this case is usually derived from BS 8233:2014 and the WHO Guidelines on Community Noise and is a single figure number with no onerous need for low frequency compliance.

    For semi-detached or terraced properties there is a need to comply with Approved Document E (ADE) of the UK Building Regulations and part of this is to make sure that shared party walls and floors between dwellings can insulate from sound to a decent enough level. It is based on research and science so that people can live together without suffering from the ill effects of noise from their neighbours, commonly footfall and furniture moving on floors and the effects of things like loud music (often with low frequency content) and voices (not so low unless you are the Hollywood voice-over man).

    As part of the compliance you need to either show the wall you are building will meet the standard by reference to approved designs (Robust Details) or by an in-situ test carried out to international standards. Rw tests are lab tests, D,nTw, Ctr tests are in-situ tests. you can look those up if you want to learn more or I’m happy to talk to you on the telephone. If you don’t pass the ADE tests you have to either re-build the wall or give up. I have worked with Barbara Jones on some of the pioneering UK semi-detached load bearing straw bale houses and they have, to my knowledge at least to the date of 2012, all failed the ADE compliance tests because of low frequency and have only passed with extra layers of stud wall being added. One particular build of three straw bale houses in a terrace has resulted in only the outer two being used with the middle one being used for storage as it could not pass compliance tests and the open plan mezzanine style of construction made remedial works were far too expensive. I hope one day it is refurbished so it can be used. It is unfortunate that many people are unwilling to listen to cold hard facts and wish to believe they can make something work they do not really know a lot about, often based on glossy self-build books with wildly inaccurate, poorly referenced, information on sound insulation.

    The drive of my studies was to stimulate debate on this as I would like to see more straw-bale building but all the while the walls are failing it will not become a mainstream building method for residential in the UK – there are already too many other things against it, like massive conventional house building conglomerates with influence on UK Govt. policy. We need established designs we know can pass (I can provide them) which involve using extra layers of stud wall or we need research to try and develop a system which will keep the wall thickness down.

    Unfortunately, as my study discovered, much of the existing published literature (websites and books on straw bales) blindly states that straw bales have super sound insulating properties. At high frequencies yes, at low frequency no: they are worse than conventional cavity brick/block walls. Unless we improve this performance, no number of apocryphal tales of super sound insulation will improve the situation.

    I just want to add I am a massive advocate of straw bale and other eco/green construction methods, which I think can solve a lot of social problems as well as ecological ones, but I am also also a scientific realist.

  37. Paul Herwin Wed, August 8, 2018 at 12:48 am #

    Andrew, one last thing – why don’t you re-write yoru post to avoid the trap of misleading people. I know you can read the comments here but people are stimulated by headlines. I am happy to help you. Really, with that extra layer of stud wall they truly are super sound insulating although probably no more than a conventional wall of a third of the thickness using the same techniques to improve performance.

  38. Steve Parry Thu, August 23, 2018 at 9:51 am #

    Hi Andrew

    I’m looking at building a recording studio in an existing (rather large) hall which is adjacent to my house. I will be having a room-within-a-room built and was thinking of using straw bales in the cavity between the existing wall and the new wall. Would the bales be ok to be exposed, as they will technically be indoors? Also, what would be the thermal benefit? The hall is, at the moment, roughly 20mx14m

    Thanks

  39. Andrew Morrison
    Andrew Morrison Tue, September 4, 2018 at 10:21 am #

    Hi Steve. I would still plaster the bales as leaving them exposed means that rodents and bugs would have direct access to them. The downside of this is that plaster makes the bales sound tinny and they will reflect sound rather than absorb it to some extent. That can all be managed with wall angles (not perpendicular to each other) and some soft coverings (tapestries, artwork, etc.). Insulation value would still be around R40 for two string bales and R50 for three, roughly.

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