6 ms·

Bricks Can Absorb Traffic Noise – Thesis Preso on Helmholtz Resonators [video]

142 points by zdw 3y ago

jauntywundrkind 3y ago
I cannot say enough how much as I've aged I've come to appreciate how lots of big dumb matters around me feels essential to have peace & quiet. You can find a peaceful out of the way place where there isn't sound or people, or you want stone and concrete aplenty around you. That's weight & mass. But that mass usually has so much cost. (And it has so many inconveinences. Where do the pipes and wires go when you are working with stone? It's not accommodating like framing & drywall.) This is so cool. This is so so so cool. It's cheating, getting one of the best & nicest things you can get, and doing it not by just cladding your world in thick concrete, but by creative use of negative spaces. By resonance. It's a vast unmaterial triumph. Using much less matter but getting so many of the same upsides. This is the arch of victory that embodies what I hope can carry us through the stars for a long time: getting so much from so little. Making stuff that is blisteringly effective. These are the triumphs that can sustain us as we voyage on. (It also looks like something that would be pretty easy to mass produce! A bit bulky to transport though, but maybe there are some creative solutions.)
- kragen 3y ago
  listen, if you want a bunch of concrete cheap, i gotta tell you people will literally pay you to haul away their construction waste, which is mostly concrete. it's almost 2 tonnes per person per year: https://www.epa.gov/smm/sustainable-management-construction-and-demolition-materials https://www.epa.gov/smm/sustainable-management-construction-... what's expensive isn't the stone and concrete. those are cheap as shit. even graded broken stone aggregate for mixing concrete is cheap. like a penny a kilogram cheap. sand, same story. random dirt is even cheaper and works fine to block sound what's expensive is shaping the concrete and dirt (for example, as you point out, to run pipes and wires through them, but also for things like making thin walls stand up stably) to a lesser extent, getting it delivered is also expensive, because it's heavy, but mostly it's the shaping. that's why concrete is so popular; concrete is mud, and mud is pretty easy to shape, but it's mud that turns into stone overnight. it turns out that it takes a lot of work to shape big things
  - schiffern 3y ago
    The low-tech "old farmer" Goldilocks solution I've seen is to mostly fill in the large gaps with free concrete rubble or stones, so a lot less (expensive) concrete is needed to infill the rest. But that ain't sexy, so most people ignore it. :) Obviously it's somewhat impractical on large jobs, and inadvisable in very strength-critical roles, but for small household / farmstead projects it's a great way to save money and get rid of ugly rubble you have lying around.
    - lnsru 3y ago
      Used bricks is very sexy solution. However it’s getting harder and harder to find old buildings to be demolished. And I wouldn’t use these bricks for critical infrastructure.
      - schiffern 3y ago
        Yeah for something you're gonna see, bricks are fantastic. If you're just making an anchor for a post or similar, rubble-infill concrete is a great cost saver.
    - mynameisnoone 3y ago
      Yep. Don't use expensive, new, pristine, energy-intensive materials wherever possible. Reserve those for finishes and exterior coatings. Appropriate filler materials should be suitable for the strength, longevity, and safety profile and function desired. This also reminds me of some DIY and volunteer experiences installing residential fence posts. On a volunteer gig, I saw people using 200 lbs. of concrete and keep adding water until it's soup triumphally proclaim it's "the right way" while dismissing supervisors and others who knew what they're doing. Meanwhile, I was looking at depth, slope, wind risk, and soil (hydrology), and gathering site debris like rocks and chunks of metal to stick under each post so it wouldn't rot in 5 years or become the Big Dig in time, materials, or quality.
      - deleted 3y ago
        [deleted]
- thworp 3y ago
  > getting so much from so little I feel the same way about directly using or mimicking systems of the natural world. Stuff like using birds as combined pest control and fertilizer or waste water treatment. I think we haven't even scratched the surface of what is possible, particularly with microbes. I envision things like producing glue, converting plant scraps into fibres/wood, converting toxins into inert compounds, extracting trace chemicals from a massive volume of useless medium. Right now I think the biggest obstacle to these kinds of techniques is the lack of control and the danger of escape and mutation. Just imagine if a plastic-eating bacterium escaped a waste facility and started eating our world. I hope that with better tools and better simulation we can make it work and make it safe. It would go a long way towards lowering our energy and resource use.
nwellinghoff 3y ago
It would seem that just making the cavern with standard solid brick and using various gaps and walls would scale better. Very interesting video I learned a lot!
Ckirby 3y ago
[flagged]
- kragen 3y ago
  plywood is too expensive for most suburb construction in the usa; instead they nail together sticks, cover them up with paper-plaster sandwiches, and wrap it in plastic to keep the plaster dry, then put some tar paper on top to keep the water out of the plastic i am not making this up, this is literally what they do
  - shiroiuma 3y ago
    Parent is probably confusing plywood with OSB. Plywood is indeed expensive (esp. high-quality types like baltic birch), but laypeople frequently use the term to refer to OSB (oriented strand board) which is much, much cheaper and is commonly used in US construction. The "paper-plaster sandwiches" you refer to is called "drywall" and is only used on interior walls. It's fine for that purpose. For outer walls, you have to use something else that's more structural, and they usually use OSB.
    - kragen 3y ago
      i have to admit to some slight exaggeration
      - shiroiuma 3y ago
        Honestly, I think American residential construction gets a lot of undeserved flak for the materials used. For the expected lifespan and the location, the materials really aren't bad; the problems I see are with workmanship quality, and the whole old-fashioned stick-building practice instead of doing more work in a factory to ensure better quality.
        kragen 3y ago
        depends on which part of america you're in; especially outside the usa, things vary enormously. most places in america, the kind of wood and paper construction that's common in the usa is only found in illegal shantytowns. legal houses are built out of brick, reinforced concrete, or occasionally adobe. so are all but the poorest houses in the shantytowns, actually
aaron695 3y ago
Normal bricks block sound. Acoustic bricks absorb sound, turning it into other energy. Commercial acoustic bricks example - https://www.randerstegl.com/en/wall-bricks/other-types-of-bricks/acoustic-bricks https://www.randerstegl.com/en/wall-bricks/other-types-of-br... So there is a Commons issue, why would I buy far more expense acoustic bricks when I can just reflect the sound, ie back at the cars. Additionally bricks collecting stagnate water is very bad, and in a urban environment collecting dust and insects is bad. Off topic but tress absorb a fair amount of noise and like Telsa's appreciate in value over time.
- worthless-trash 3y ago
  > when I can just reflect the sound, ie back at the cars. The problem (i think) is that the people (buyers?) may spend time in the area where the sound is reflected.
  - giantg2 3y ago
    And you're reflecting to your neighbors across the street. A lot of times vehicle noise is less noticeable in the country because you don't have brick buildings lining the street to create an echo chamber.
- thatguy27 3y ago
  Are there datasheets and/or design guides for the bricks you linked to?
pengaru 3y ago
Congrats on solving the vermin housing problem
vincnetas 3y ago
Im am anti car zealot. I'm labelling so my self auto-ironically (no pun intended), as i own a car, but i prefer cities with less cars. I'm angry how often we externalise damage generated by cars to someone else. We are technically capable to produce silent cars, yet we somehow try to workaround this by building houses of different materials? How backwards that is instead of just legally limiting the sound levels for newly produced cars. And eventually cars will have only rolling noice. But then someone would say oh but then cars are dangerous when they are silent, let's install speakers in them so pedestrians can hear approaching car and move out of the way. See what's happening here? Instead of jus making a car unable (auto breaks) to hit a pedestrian, we are doing some silly workarounds (ok, no silly but cost saving) to emit noise and shift the burden of moving out of the way to the pedestrian. Again polluting city with noice. Done ranting. Have not touched pollution, wight, speed limits and general car infrastructure :) Time to get my morning coffee. P.S yes, i'm very much influenced by "Not Just Bikes". Youtube channel about European city planning (human/bike oriented) https://www.youtube.com/c/notjustbikes https://www.youtube.com/c/notjustbikes
- atoav 3y ago
  Societies thinking around cars really shows just how "unnoticeable" the influence of something becomes once it is ubiquitous. In a car-based world everything takes the shape of cars, and the crazy thing is, that many people won't even see how unusual that is. I once lived next to a busy inrush road in a city. Once a week I could wipe black grime from my balcony desk. Every second night I would wake up from people speeding or trucks rushing through. One day I spent on the balcony counting cars. 100% of the SUVs had only one person in it. But the worst thing was the noise. I didn't notice back then, and I am not a sensitive person (I play in a noise rock band), but when I moved and was in a silent new flat, it felt as if someone had lifted a rock from my chest. And let's not think about the black grime. Cities and cars are not a good mix, unless you own a car and don't care about the people living there. I especially dislike how naturally we are expected to yield public space to ever-bigger cars for only minor fees.
  - Ma8ee 3y ago
    What I find most striking is that people with very rudimentary training are allowed to use machinery of 1.5 tons and more, in public, in the vicinity of unprotected bystanders. This leads to about 43,000 deaths per year in the US alone. And for some reason this is considered normal.
unglaublich 3y ago
Wouldn't it be cheaper to limit manufacturers from producing needlessly loud vehicles? We _know_ we can do it, but we _still_ allow idiotic V8 trucks, 2500kg SUVs with double turbos, Harley Davidsons that are _designed_ to be as loud as possible. Stop making so much noise!
- deleted 3y ago
  [deleted]
- ricardobayes 3y ago
  The most noisy ones imo are the dirt bikes with no mufflers. Those can be heard from miles away. Or those 50cc scooters young lads ride on.
  - bigfudge 3y ago
    Bikes with no mufflers are already breaking the law. We should actually enforce those laws
- serf 3y ago
  a bit of humor here for me : both bigger engines and turbos generally reduce noise pollution when compared to the other design choices available for that power envelope. the loudest engine? a small literage non-turbo high compression motor of some sort. the most famously loud race-car , the mazda 787b, had a 2.6 liter naturally aspirated motor. Small literage, small package, rotary. Fairly high compression. It deafened drivers. turbochargers can be made to be annoying by enthusiasts, sure -- but that energy they produce is in large part thanks to the damping effect of the energy scavenging that they enable. and as for engine size, as literage increases an engine developer has to do less to get the power they need -- that means they can use long and heavily dampened mufflers/exhaust systems, lower compression, lower RPM, less noise . Again, yes -- enthusiasts can ruin this, but the larger majority of these big motors are quieter/smoother than their counterparts that must go to extremes to meet the same power criteria.
  - bigfudge 3y ago
alfajoe 3y ago
[flagged]
nliang86 3y ago
Text outline with chapter breakdowns and key images for those that prefer it: https://www.videogist.co/videos/these-bricks-can-absorb-traffic-noise-thesis-presentation-on-helmholtz-resonators-2426 https://www.videogist.co/videos/these-bricks-can-absorb-traf...
- ajot 3y ago
  Thank you! I missed the show HN on your project, but it looks fantastic (and I like its promotion through HN comments for long-ish form videos, doesn't feel spammy, is helpful and very clear to understand what it does).
phasetransition 3y ago
Helmholtz absorbers have been used for some time in built spaces. Look for a pattern of slats or holes like perfboard, often on the rear wall of the space. Lecture halls, museums, performing arts, and the like. Commercial helmholtz CMU products: https://www.soundseal.com/masonry https://www.soundseal.com/masonry https://www.rpgeurope.com/products/product/diffusorblox.html https://www.rpgeurope.com/products/product/diffusorblox.html
- phil21 3y ago
  I've seen the top picture installed in a few places, and always wondered what their function was. Learn something new every day, and this time it was 10 minutes after I woke up! Thanks!
- adolph 3y ago
  The author acknowledges present use and also gives intriguing historical examples from Vitruvius and and Da Vinci. An acoustic jar, also known by the Greek name echea (ηχεία, literally echoers), or sounding vases, are ceramic vessels found set into the walls, ceilings, and sometimes floors, of medieval churches. They are believed to have been intended to improve the sound of singing, and to have been inspired by the theories of Vitruvius. https://en.wikipedia.org/wiki/Acoustic_jar https://en.wikipedia.org/wiki/Acoustic_jar
- oniony 3y ago
  Yes, this is covered in the video. He talks about use in antiquity and in modern buildings. https://www.youtube.com/watch?v=y9-p4AkgVU8&t=407s https://www.youtube.com/watch?v=y9-p4AkgVU8&t=407s
bannedbybros 3y ago
[dead]
fudged71 3y ago
While I love technology, and I know they were given a challenge to use ceramics, I’d like to see this approach compared with foliage
ethagknight 3y ago
I cannot for the life of me figure out why they would not have simply cast bricks with an inflated balloon or plastic bag inside? They could even still do the inside/outside resonator combo which is a neat trick too. I laughed out loud when they were using the big robot arm to do the texturing. Use your friggin hands.

142 points by zdw 3y ago

I cannot say enough how much as I've aged I've come to appreciate how lots of big dumb matters around me feels essential to have peace & quiet. You can find a peaceful out of the way place where there isn't sound or people, or you want stone and concrete aplenty around you. That's weight & mass. But that mass usually has so much cost. (And it has so many inconveinences. Where do the pipes and wires go when you are working with stone? It's not accommodating like framing & drywall.) This is so cool. This is so so so cool. It's cheating, getting one of the best & nicest things you can get, and doing it not by just cladding your world in thick concrete, but by creative use of negative spaces. By resonance. It's a vast unmaterial triumph. Using much less matter but getting so many of the same upsides. This is the arch of victory that embodies what I hope can carry us through the stars for a long time: getting so much from so little. Making stuff that is blisteringly effective. These are the triumphs that can sustain us as we voyage on. (It also looks like something that would be pretty easy to mass produce! A bit bulky to transport though, but maybe there are some creative solutions.)

kragen 3y ago
listen, if you want a bunch of concrete cheap, i gotta tell you people will literally pay you to haul away their construction waste, which is mostly concrete. it's almost 2 tonnes per person per year: https://www.epa.gov/smm/sustainable-management-construction-and-demolition-materials https://www.epa.gov/smm/sustainable-management-construction-... what's expensive isn't the stone and concrete. those are cheap as shit. even graded broken stone aggregate for mixing concrete is cheap. like a penny a kilogram cheap. sand, same story. random dirt is even cheaper and works fine to block sound what's expensive is shaping the concrete and dirt (for example, as you point out, to run pipes and wires through them, but also for things like making thin walls stand up stably) to a lesser extent, getting it delivered is also expensive, because it's heavy, but mostly it's the shaping. that's why concrete is so popular; concrete is mud, and mud is pretty easy to shape, but it's mud that turns into stone overnight. it turns out that it takes a lot of work to shape big things
- schiffern 3y ago
  The low-tech "old farmer" Goldilocks solution I've seen is to mostly fill in the large gaps with free concrete rubble or stones, so a lot less (expensive) concrete is needed to infill the rest. But that ain't sexy, so most people ignore it. :) Obviously it's somewhat impractical on large jobs, and inadvisable in very strength-critical roles, but for small household / farmstead projects it's a great way to save money and get rid of ugly rubble you have lying around.
  - lnsru 3y ago
    Used bricks is very sexy solution. However it’s getting harder and harder to find old buildings to be demolished. And I wouldn’t use these bricks for critical infrastructure.
    - schiffern 3y ago
      Yeah for something you're gonna see, bricks are fantastic. If you're just making an anchor for a post or similar, rubble-infill concrete is a great cost saver.
  - mynameisnoone 3y ago
    Yep. Don't use expensive, new, pristine, energy-intensive materials wherever possible. Reserve those for finishes and exterior coatings. Appropriate filler materials should be suitable for the strength, longevity, and safety profile and function desired. This also reminds me of some DIY and volunteer experiences installing residential fence posts. On a volunteer gig, I saw people using 200 lbs. of concrete and keep adding water until it's soup triumphally proclaim it's "the right way" while dismissing supervisors and others who knew what they're doing. Meanwhile, I was looking at depth, slope, wind risk, and soil (hydrology), and gathering site debris like rocks and chunks of metal to stick under each post so it wouldn't rot in 5 years or become the Big Dig in time, materials, or quality.
    - deleted 3y ago
      [deleted]
thworp 3y ago
> getting so much from so little I feel the same way about directly using or mimicking systems of the natural world. Stuff like using birds as combined pest control and fertilizer or waste water treatment. I think we haven't even scratched the surface of what is possible, particularly with microbes. I envision things like producing glue, converting plant scraps into fibres/wood, converting toxins into inert compounds, extracting trace chemicals from a massive volume of useless medium. Right now I think the biggest obstacle to these kinds of techniques is the lack of control and the danger of escape and mutation. Just imagine if a plastic-eating bacterium escaped a waste facility and started eating our world. I hope that with better tools and better simulation we can make it work and make it safe. It would go a long way towards lowering our energy and resource use.

nwellinghoff 3y ago

It would seem that just making the cavern with standard solid brick and using various gaps and walls would scale better. Very interesting video I learned a lot!

Ckirby 3y ago

[flagged]

kragen 3y ago
plywood is too expensive for most suburb construction in the usa; instead they nail together sticks, cover them up with paper-plaster sandwiches, and wrap it in plastic to keep the plaster dry, then put some tar paper on top to keep the water out of the plastic i am not making this up, this is literally what they do
- shiroiuma 3y ago
  Parent is probably confusing plywood with OSB. Plywood is indeed expensive (esp. high-quality types like baltic birch), but laypeople frequently use the term to refer to OSB (oriented strand board) which is much, much cheaper and is commonly used in US construction. The "paper-plaster sandwiches" you refer to is called "drywall" and is only used on interior walls. It's fine for that purpose. For outer walls, you have to use something else that's more structural, and they usually use OSB.
  - kragen 3y ago
    i have to admit to some slight exaggeration
    - shiroiuma 3y ago
      Honestly, I think American residential construction gets a lot of undeserved flak for the materials used. For the expected lifespan and the location, the materials really aren't bad; the problems I see are with workmanship quality, and the whole old-fashioned stick-building practice instead of doing more work in a factory to ensure better quality.
      - kragen 3y ago
        depends on which part of america you're in; especially outside the usa, things vary enormously. most places in america, the kind of wood and paper construction that's common in the usa is only found in illegal shantytowns. legal houses are built out of brick, reinforced concrete, or occasionally adobe. so are all but the poorest houses in the shantytowns, actually

aaron695 3y ago

Normal bricks block sound. Acoustic bricks absorb sound, turning it into other energy. Commercial acoustic bricks example - https://www.randerstegl.com/en/wall-bricks/other-types-of-bricks/acoustic-bricks https://www.randerstegl.com/en/wall-bricks/other-types-of-br... So there is a Commons issue, why would I buy far more expense acoustic bricks when I can just reflect the sound, ie back at the cars. Additionally bricks collecting stagnate water is very bad, and in a urban environment collecting dust and insects is bad. Off topic but tress absorb a fair amount of noise and like Telsa's appreciate in value over time.

worthless-trash 3y ago
> when I can just reflect the sound, ie back at the cars. The problem (i think) is that the people (buyers?) may spend time in the area where the sound is reflected.
- giantg2 3y ago
  And you're reflecting to your neighbors across the street. A lot of times vehicle noise is less noticeable in the country because you don't have brick buildings lining the street to create an echo chamber.
thatguy27 3y ago
Are there datasheets and/or design guides for the bricks you linked to?

pengaru 3y ago

Congrats on solving the vermin housing problem

vincnetas 3y ago

Im am anti car zealot. I'm labelling so my self auto-ironically (no pun intended), as i own a car, but i prefer cities with less cars. I'm angry how often we externalise damage generated by cars to someone else. We are technically capable to produce silent cars, yet we somehow try to workaround this by building houses of different materials? How backwards that is instead of just legally limiting the sound levels for newly produced cars. And eventually cars will have only rolling noice. But then someone would say oh but then cars are dangerous when they are silent, let's install speakers in them so pedestrians can hear approaching car and move out of the way. See what's happening here? Instead of jus making a car unable (auto breaks) to hit a pedestrian, we are doing some silly workarounds (ok, no silly but cost saving) to emit noise and shift the burden of moving out of the way to the pedestrian. Again polluting city with noice. Done ranting. Have not touched pollution, wight, speed limits and general car infrastructure :) Time to get my morning coffee. P.S yes, i'm very much influenced by "Not Just Bikes". Youtube channel about European city planning (human/bike oriented) https://www.youtube.com/c/notjustbikes https://www.youtube.com/c/notjustbikes

atoav 3y ago
Societies thinking around cars really shows just how "unnoticeable" the influence of something becomes once it is ubiquitous. In a car-based world everything takes the shape of cars, and the crazy thing is, that many people won't even see how unusual that is. I once lived next to a busy inrush road in a city. Once a week I could wipe black grime from my balcony desk. Every second night I would wake up from people speeding or trucks rushing through. One day I spent on the balcony counting cars. 100% of the SUVs had only one person in it. But the worst thing was the noise. I didn't notice back then, and I am not a sensitive person (I play in a noise rock band), but when I moved and was in a silent new flat, it felt as if someone had lifted a rock from my chest. And let's not think about the black grime. Cities and cars are not a good mix, unless you own a car and don't care about the people living there. I especially dislike how naturally we are expected to yield public space to ever-bigger cars for only minor fees.
- Ma8ee 3y ago
  What I find most striking is that people with very rudimentary training are allowed to use machinery of 1.5 tons and more, in public, in the vicinity of unprotected bystanders. This leads to about 43,000 deaths per year in the US alone. And for some reason this is considered normal.

unglaublich 3y ago

Wouldn't it be cheaper to limit manufacturers from producing needlessly loud vehicles? We _know_ we can do it, but we _still_ allow idiotic V8 trucks, 2500kg SUVs with double turbos, Harley Davidsons that are _designed_ to be as loud as possible. Stop making so much noise!

deleted 3y ago
[deleted]
ricardobayes 3y ago
The most noisy ones imo are the dirt bikes with no mufflers. Those can be heard from miles away. Or those 50cc scooters young lads ride on.
- bigfudge 3y ago
  Bikes with no mufflers are already breaking the law. We should actually enforce those laws
serf 3y ago
a bit of humor here for me : both bigger engines and turbos generally reduce noise pollution when compared to the other design choices available for that power envelope. the loudest engine? a small literage non-turbo high compression motor of some sort. the most famously loud race-car , the mazda 787b, had a 2.6 liter naturally aspirated motor. Small literage, small package, rotary. Fairly high compression. It deafened drivers. turbochargers can be made to be annoying by enthusiasts, sure -- but that energy they produce is in large part thanks to the damping effect of the energy scavenging that they enable. and as for engine size, as literage increases an engine developer has to do less to get the power they need -- that means they can use long and heavily dampened mufflers/exhaust systems, lower compression, lower RPM, less noise . Again, yes -- enthusiasts can ruin this, but the larger majority of these big motors are quieter/smoother than their counterparts that must go to extremes to meet the same power criteria.
- bigfudge 3y ago

alfajoe 3y ago

[flagged]

nliang86 3y ago

Text outline with chapter breakdowns and key images for those that prefer it: https://www.videogist.co/videos/these-bricks-can-absorb-traffic-noise-thesis-presentation-on-helmholtz-resonators-2426 https://www.videogist.co/videos/these-bricks-can-absorb-traf...

ajot 3y ago
Thank you! I missed the show HN on your project, but it looks fantastic (and I like its promotion through HN comments for long-ish form videos, doesn't feel spammy, is helpful and very clear to understand what it does).

phasetransition 3y ago

Helmholtz absorbers have been used for some time in built spaces. Look for a pattern of slats or holes like perfboard, often on the rear wall of the space. Lecture halls, museums, performing arts, and the like. Commercial helmholtz CMU products: https://www.soundseal.com/masonry https://www.soundseal.com/masonry https://www.rpgeurope.com/products/product/diffusorblox.html https://www.rpgeurope.com/products/product/diffusorblox.html

phil21 3y ago
I've seen the top picture installed in a few places, and always wondered what their function was. Learn something new every day, and this time it was 10 minutes after I woke up! Thanks!
adolph 3y ago
The author acknowledges present use and also gives intriguing historical examples from Vitruvius and and Da Vinci. An acoustic jar, also known by the Greek name echea (ηχεία, literally echoers), or sounding vases, are ceramic vessels found set into the walls, ceilings, and sometimes floors, of medieval churches. They are believed to have been intended to improve the sound of singing, and to have been inspired by the theories of Vitruvius. https://en.wikipedia.org/wiki/Acoustic_jar https://en.wikipedia.org/wiki/Acoustic_jar
oniony 3y ago
Yes, this is covered in the video. He talks about use in antiquity and in modern buildings. https://www.youtube.com/watch?v=y9-p4AkgVU8&t=407s https://www.youtube.com/watch?v=y9-p4AkgVU8&t=407s

bannedbybros 3y ago

[dead]

fudged71 3y ago

While I love technology, and I know they were given a challenge to use ceramics, I’d like to see this approach compared with foliage

ethagknight 3y ago

I cannot for the life of me figure out why they would not have simply cast bricks with an inflated balloon or plastic bag inside? They could even still do the inside/outside resonator combo which is a neat trick too. I laughed out loud when they were using the big robot arm to do the texturing. Use your friggin hands.