ACOUSTIC TREAMENT

For our third and final project we were tasked with acoustically treating a space on a budget using calculations and techniques learned in class. Using other software and calculators, like an RT60 calculator, we were to determine certain problem areas in the space that would need acoustic treatment. Comparisons for both the untreated and treated versions of the spaces needed to be made as well as comparisons of between the treated room on a budget and a professionally treated room. Planning and explanations are also to be included.

The space I chose for this project was my bedroom at home which is also where I mix from time to time. This space had a rough length of 4.5 meters, a width of 3.4 meters, and a height of 3.15 meters. The floor has carpet, the walls are made of plaster, there is a recess at the front of the room where the casement windows sit, and the door is on the left side of the room made of a wooden frame with a glass middle.

For the contents of the room, on the left side at the back there is a clothes rack with hanging clothes, shoes and shoeboxes sitting on top with a dirty clothes basket full of clothes in the corner. At the front of the left side of the room is a chest of drawers made of wood, with a mirror on top of it, before the recess. Within the recess there is a desk with my studio monitors and midi keyboard on top. Surrounding it on the left, back and right sides are various PC boxes. To the right of the recess is a small table with my PC and all the way to the back on the right side of my room is a bedside table made of wood. Finally my queen sized mattress and bed base lay pressed against the back of the wall directly behind my desk.

DIMENSIONS OF ROOM:

H= 3.15m (54 hz resonant freq), W= 3.4m (50hz resonant freq),L= 4.5m (38hz resonant freq)

Average fundamental freq= 47.3 hz

With the results I had gathered and some in depth research into budget friendly acoustic treatment I conducted over the course of 2-3 weeks (FIND RESEARCH IN THE NOTES SECTION OF WEEK 9 AND WEEK 10), I drew up a rough plan of the acoustic treatment I was going to source/make for my room. There were two rough plans for the acoustic treatment, a projected plan and a back up plan. The projected plan was the acoustic treatment I wanted to build and implement with the research I had gathered if there were no hiccups or major setbacks. The back up plan was for the acoustic treatment I could source and apply if my time constraints were an issue (didn't have enough time to source the resources) or if what I had planned failed.

Both plans are rough plans and is not set in stone where everything is going to be placed. Using the mirror trick along the bare right side of the wall I'll find the most prominent 3 spaces to place the acoustic absorption panels, I will have built myself, along the wall. The panels will also be placed using the mirror trick (or finding the standing waves present in the room) around the room with one being definitely hung on my door. These panels will have acoustic insulation in them (earth wool) and will have a breathable fabric wrapped around their pine frame to allow sound to travel through.

Filling the gaps between the acoustic panels will be cheap acoustic foam placed in a checkered pattern to help diffuse and absorb small amounts of sound. These will also be placed either side of the diffuser above my mattress and behind my speakers and desk to help with treating some of the bass frequencies along with the PC boxes I have. The acoustic foam will be sourced affordably from Facebook Marketplace.

Directly facing the speakers, on the back wall of the room above my mattress, is where the skyline diffuser I will be building will sit. The skyline diffuser will be made out different length 42x42mm pine cubes that are stuck to an MDF backboard. This diffuser will scatter the sound coming from the speakers making the reflections weaker and whatever reflections towards the mattress will be completely absorbed. Pine was chosen as the timber for the diffuser as it has a warm tone in the mid range as stated in a video "How To Build A Sound Diffuser" (Acoustic Fields, 2018) displayed in my week 9 notes here . The calculation for the diffuser was a little confusing so I inputted the diffuser calculator (Calculate Skyline Diffusor with given Frequencies, n.d.) to target the frequencies between 2000hz and 5000hz. Displayed below. The method for building the diffuser as well as the calculator was explained during the video "How to build an acoustic diffuser" (How to Build an Acoustic Diffuser, 2013) .

For the bass traps my mom brought over some thick cushions, which will be placed in the corner with either two of them flush against the corner in an L shape or will be facing directly out from the corner where they can be stacked on top of one another to capture more of the bass frequencies. These will be especially useful in the back and front of the right side corners and within the corners of the recess behind the speakers. The cushions are thick and large and will be excellent for trapping some of the bass.

A heavy curtain or blanket will be covering the windows to stop any sound reflecting off the glass and back into my ears. If I am unable to attain a heavy thick curtain for an affordable price I will settle for a throw over blanket I have that its quite thick and would have a great absorption co efficient.

Unfortunately for the door, it already has lots of problems with keeping shut. So trying to make the door as air tight as possible will prove to be a challenge. At this stage I will be rolling up a towel tightly and placing it at the bottom of the door where there is a gap between the door and the floor for airflow to pass through.

PROCESS: CONSTRUCTING THE TREATMENT

Most of the treatment for acoustically treating my room is meant to be sourced from family, friends, a seller on Facebook Marketplace and, from my own home. However, I wanted to challenge myself by constructing some treatment which I may possibly go on to use in my room for a while to come.

THE SOUND DIFFUSER

The sound diffuser was the most straight forward and easiest to make, but probably the most tedious and time consuming as well. As I wanted a diffuser that was going to be a meter long and half a meter tall I had to make two separate 500mm x 500mm diffusers and then hang them right next to each other. After calculating the measurements of the 4 different sized pieces of timber, I sought the help of my friend who had a drop saw and other woodwork tools.

We cut each of the three 1.8 meter poles into the 4 measurements the calculator had provided and then copied the grid, of where each individual piece of cut timber was going to be placed, on to the two MDF backboards. During this process I realized I had not calculated correctly and that the blocks of timber were just a little too big for how much MDF I had cut. It wasn't a big hassle however as we just cut the back board to fit 11 blocks up and across rather than 12. This may effect the efficiency of the diffuser.

To finish the diffuser, the blocks were each sanded so they could fit next to each other with ease and didn't have any sharp bits sticking out. This was a very long and tedious process. After they were sanded they were placed and glued carefully with wood glue to the MDF backboard where each of the blocks were meant to sit on the grid. It was halfway through gluing the blocks onto the backboard that I realized that I didn't have enough blocks for the second backboard; I hadn't doubled the amount of beams I had to get like I did when I got MDF boards. In the end I managed to get the necessary beams and construct the second diffuser.

THE ACOUSTIC PANELS

Making the acoustic panels proved to be the most lengthy and convoluted process out of everything as it required timber, brackets, screws, fabric and a lot of annoying manpower. The inspiration and loosely based method came from the "DIY Acoustic Panels" (DIY Acoustic Panels - How To Make Your Own Cheap and Awesome Panels, 2018) on YouTube. When measuring the dimensions for the panel frames, I had to take into consideration the dimensions of the earth wool insulation slabs (L=1160mm x W= 450mm x T= 90mm ) I had purchased. My friend and I used a slab of the earth wool to place the timber around the insulation so we could mark out the measurements we needed so we could cut the timber into dimensions that would fit the insulation nice and snug.

The process of cutting the timber was easy, it was the drilling of the brackets and screws that was a long and somewhat uncomfortable process. It wasn't easy holding the frames in place and drilling brackets in place with the screws; it took about 3 to 4 hours to finish the frames. One these frames were constructed it was time to install the insulation into the frames. When situating the insulation into the frames I noticed that the earth wool was not 90mm thick as it was displayed (this could be due to the slabs being compressed by the packaging), either they sat nicely in the frames but I was worried about them moving back and forward.

To counter this I split another slab in half and placed it on top to provide it with extra thickness so it wouldn't move back and fourth within the frame. After all, I had 14 lots of earth wool which is more than double what I needed. Once the insulation was placed within the frames I measured the canvas fabric that was going to be the main fabric that wrapped around the frame. For the canvas fabric I had to buy a total of 10 meters as there was no way I could use the fabric to wrap all six frames with minimal waste. Pulling tight the canvas material I was able to create a tight fit so the insulation didn't move and stapled the canvas to lining of the back sides of the frames. At the end I stapled some hessian fabric, which was dirt cheap, to the back of the panel and cut it to the shape of the frame. This meant the insulation had no way of moving or pushing out from the back of the frame.

PROCESS: SOURCED TREATMENT

The acoustic treatment that was not built but sourced came from a mixture of at home items and items that were purchased. I tried to find as many budget friendly items to use as I didn't want to break the bank on this projects. We were tasked to acoustically treat our rooms on a budget after all.

THROW OVER BLANKET (ACOUSTIC CURTAIN)

The bare walls, corners and the recess in my room were all problem areas but my window was probably the worst as sound would reflect off it and bounce between the back wall ad the window and create some standing waves throughout the space. As I couldn't really afford to buy curtains and I was already building a diffuser along with the acoustic panels, making curtains probably wasn't ideal considering the time constraints. The living room had a big wool/cotton throw over which would be great to hang on my curtain rod on my window. I decided this was going to cover up my window, eliminating a massive problem.

PROCESS: APPLYING THE TREATMENT

Having all my treatment constructed and sourced, it was time to apply the acoustic treatment. First thing I wanted to test was if the acoustic foam stuck to the wall with double sided tape/adhesive; it didn't. This could of been something I could of researched more into before committing, but like I previously mentioned it was an after thought and I was strapped for time. I cut an 1100mm x 280mm piece of the acoustic foam to be saved for later.

Before applying any treatment I played a 50hz, 100hz, 150hz and, 200hz sine wave through my monitors to identify where some of the standing waves may be located to apply the appropriate treatment. I found there were many areas where the sine waves would be barely audible and others where it would extremely loud, especially behind the speakers, in the corners and along the bare right side of the wall. I cross referenced this information with the mirror trick that me and my housemate executed to find the first reflections to add the acoustic treatment (I am not confident I did it correctly however).

Like I previously mentioned, one of the major problem areas was my rooms recess at the front of my room and my desk (my sweet spot) was fitted in that space. To help rectify this, I brought my desk out of the recess so it was in line with the walls either side of the recess. This would give the monitors on the desk enough room for the soundwaves to hit the window. However, I didn't want the sound to hit the window, I wanted the sound to be absorbed, so I clamped the throw over to my curtain rod so it was completely covering my window. That act alone changed the energy of the room and the acoustics.

To help with cleaning up some of the low frequencies and powerful standing waves behind the monitors, I placed the computer boxes at different heights around the back of the desk and around the speakers to give the recess more absorption and diffusion properties. There were many different shaped boxes, which worked out in my favor, and they all had more or less some absorption qualities to help with trapping those nasty low frequencies that were so present in the recess.

Next up was the bass traps (the cushions). They were a bit awkward to place so a lot of the process was going to be through trial and error. Starting with the recess I managed to stack a back cushion on top of the black cushion either side of the recess's corners; these were facing diagonally in the corner so that the sound would be absorbed straight into the face of the cushions and be mostly trapped and weakened in the gap between the cushion and the wall. I also wanted the cushions to be the same height as my head in my sweet spot.

The same was applied to the back right corner of my room, where the bedside table was before I moved it for the treatment. The difference between this bass trap was that I rolled up the larger leftover part of the acoustic foam to create bass cylinder and placed it between the back of the cushions and the wall. This was applied to that corner of the room as it was a major problem area and there wasn't much to absorb the sound in that area of the room. Whatever sound is transmitted through that bass trap and into the acoustic foam cylinder would get trapped, bounce around and wouldn't be able to escape.

On the other side of the room, this wasn't needed as there was a rack full of clothes and dirty clothes basket full of clothes that would absorb a lot of the sound in that area of the room. Under my PC table that was located by the right side corner of the front of the room, just before the recess, I placed my foam roller behind another cushion for another bass trap.

Moving onto the diffuser, I was at a loss how I was going to place the diffuser at head level without trying to hang it at the back of the room. The diffuser(s) are heavy, and for them to hang on the wall they would need to be drilled in, which simply cannot happen due to my house being a rental. They are also too heavy to be hung as they damage the paint on the wall. As this wasn't a permanent treatment I decided to place it on top of two boxes on my bed with my bed pillows to cover the reflective parts of the boxes. The pillows would absorb the sound while the sound diffuser would scatter the sound that hit it from the speakers. As I wasn't too sure where the strip of acoustic foam I had cut would sit, I placed it above the diffuser to absorb some of the sound coming from the monitors.

Speaking of my bed, I positioned the mattress directly in front of the speakers so that a good portion of the sound would be absorbed by the mattress evenly. Finally it was time to place the acoustic panels, but seeing as I didn't put a back piece and hook hole on the back of the acoustic panels...I couldn't hang them up. When I used the mirror trick to find the first reflection points, I put an object to mark where the panels needed to sit. Using chairs I stood the panels against the wall in the place where the first reflection points were marked out.

There were two either side of the sweet spot, I used the double insulated panels for either side as I wanted them to absorb a lot of the reflections. Including the panel on the right side of the sweet spot, I placed 3 acoustic panels along the right side of the wall where the reflection points were. Another was placed on top of the bed side table at the back left side of the room and the last one was placed on another chair on the door when shut. There was also an extra cushion so I added right next to the left hand side sweet spot panel on top of the chest of drawers where the mirror was located.

To close the gap between the floor and bottom of the door I rolled up a towel and placed it at the seal. Finally it was time to test the acoustics and as before, I used claps and speaking 1 meter away from my recording device as evidence (find attached below).

CONCLUSION

RESULTS

Through planning and fine detail, I was presently surprised to hear the space sound close to what I had envisioned it would sound like. I wasn't expecting drastic improvements as the ceilings are high and I can only treat so much of my room, but I was afraid of there being little to no difference in the acoustics after all the time and work I had out into treating the room.

When clapping you can hear a lot of the reverb is gone and there isn't such a prominent low end. The reverbs tail is almost none existent, it's there but it's very faint which is what I want. There is still a noticeable high end, but that would be mostly due to the ceilings and upper walls not being treated. The lack of deliberate diffusion also would play a role in why the high frequencies linger, albeit shorter than they were before.

This house is a rental unfortunately which means a lot of the treatment is placed awkwardly to avoid damaging the space. That being said, the treatment is working the no less better than if it was properly placed on the walls and corners. One thing that is lacking is proper airflow. I found myself not getting enough oxygen which lead me to having some dizziness when I stayed in the room for over an hour without a breath of fresh air.

BEST CASE SCENARIO

Consider this to be the worst case scenario, which it probably is, what would the best case scenario look like for this space? Well for starters it would require a much bigger budget anywhere up wards from $10,000. As the house is an old house it might be beneficial to build a room within a room. Using the correct materials, I would seal off the recess of the room while also having 4 bevel corners to reduce the low frequency build up that would usually occur in your common square corners in rooms. The flooring would still be carpet but the floor would be slightly elevated from the ground of the room.

For the acoustic treatment of the space, I would opt for the walls of the inner room to be lined with sound proofing insulation (rockwool, earth wool or fiberglass) but there would still be a space between the outer wall of the inner room and the room that the inner room sits in. This is so that the sound will be trapped within both walls and won't be able to escape, similar to my bass traps.

The inner room would still have a high ceiling so that the reflections have a distance to travel up and down. There wouldn't be a bed or any other personal furniture in the room to help with the acoustics but there would be a custom designed diffuser created to target the rooms problem frequencies. The bass traps and acoustic panels would all be made of premium grade rockwool and acoustic foam which would significantly improve the space's acoustics. The bass traps would connect from the floor all the way to the ceiling and the acoustic panels would be larger and more numerous. Some would be located on the ceilings and others on the wall.

The door that connects to the outside of the room would need to be air tight and have the ability to completely seal off the space from the outside. This would be to minimize the sound from leaking out or leaking in. As this would of course limit the amount of oxygen that would be supplied to the room, there would need to be some sort of air ventilation to keep a decent supply circulating.

REFLECTION

When overviewing the projects for AUD175 this project was the project which caught my eye. It didn't disappoint. The project pushed me out of my comfort zone and challenged me in a lot of different ways compared to the previous projects. I think it has something to do with the practicality of the project mixed with the technicality that was required. This was also our first solo project and I quite enjoyed taking responsibility and accountability of my own work.

Even though I have submitted this project a couple hours late due to circumstances out of my control, I have to admit that my time management has been a lot better this time around. From the start I wanted to make sure I had a clear concise plan that I could work from so that I could delegate enough time to complete everything on time, because I had a lot of challenges to overcome. An example was that I knew taking the necessary time to source the materials to build the diffuser and panels as well as construct them would take up most of my time on this project. So as I progressed with the project I documented and wrote up my Project 3 page instead of waiting until after I had applied the treatment to write my project up.

I wanted to challenge myself by doing the best I could in the timeframe we were given which is why I opted to building a diffuser and acoustic panels. I wanted to see if was capable of accomplishing such a feat. That gamble paid off and I am very happy with the fruits of my labor. I'd go as far to say this us probably my best work of the entire trimester and this is a perfect example of deliberate practice and professional skills.

Under estimating how much some of the materials cost was probably my biggest downfall during this project. All up I think I spent upwards of $300 on everything, which if you look at the result is actually a very acceptable amount of spending, but as I am on a part time wage it did leave a little dent in my wallet. I'd also say that over thinking every minuet detail about this project was also something that could of been avoided. At the end of the day, this was just a project and if it didn't work the way I had planned than I would've documented it and taken it on board as a lesson. That is my perfectionist side that tends to creep through often although, I looking inwards and trying overcome this.

To be honest however, I don't think much went wrong. I didn't necessarily have an expectation I was just curious to see how this project would turn out and I think that worked out the best for me. It's good to know that I not only took away the knowledge from the experience of this project but also that I have acoustically treated my room which will be great for my own creative projects. The energy in the room is a lot different.

Given more time I would of looked at more options for hanging the frames and making some more aesthetically pleasing bass traps. Same goes for the curtains, I would of liked to actually make my own weighted curtains so they blended in my room a little better. These however can all be improved on later on, so I'm not super fussed. There's also the possibility that I am going to rebuild a lot of the acoustic treatments into better functioning out of better quality materials in the future.

As this was my final project, I don't think there's anything I need to learn but there are things I need to reflect on. There is a lot that was covered over the three projects that I could probably revise on for a better understanding, including acoustics. Whether or not I dive down the rabbit hole of further study of the topics covered in class is another story, I can't guarantee over my break I will keep this level of curiosity as I am very mentally exhausted from this trimester but, who knows? Acoustic treatment really interests me and I'd really like to look into it more if I get the chance to over the break.

REFERENCES

• Acoustic Fields. (2018, March 23). How To Build A Sound Diffuser - www.AcousticFields.com [Video]. YouTube. https://www.youtube.com/watch?v=jak-W8x6c3g

• How to build an acoustic diffuser. (2013, May 8). [Video]. YouTube. https://www.youtube.com/watch?v=oHTmNyo_0O0

• DIY Acoustic Panels - How To Make Your Own Cheap and Awesome Panels. (2018, March 24). [Video]. YouTube. https://www.youtube.com/watch?v=tLk6fQVcoSw&t=651s

• Calculate Skyline Diffusor with given frequencies. (n.d.). HiFi Audio Design. Retrieved September 1, 2021, from http://www.mh-audio.nl/Acoustics/DiffusorCalculator.asp