Last Fall, downsizing to a convertible studio with a separate bed nook felt like a step towards cozy living. However, that illusion was shattered the first morning. Each footstep in the hallway reverberated like a loudspeaker through the gap beneath the solid door. I’d naively blocked similar gaps in past apartments, only to suffer air quality issues. Understanding the crucial role this gap plays in building ventilation, thanks to stack effect, I began a mission to mitigate the noise issue without sacrificing fresh air. The gap’s other connected issues and my attempts to address them, are a story for another time.
After deciding to make a partial wall to hide the nook for reasons connected to Black Hat Feng Shui, I realized I could give it an additional purpose by including sound absorption. After a small amount of research, I created a model to be filled with hexagonal infill. After printing the model a couple of times, I felt that something was wrong. The model required too much time to print and I had doubts about the infill’s ability to block sound. I conducted more research, learning that cotton batting had a much better chance of blocking sound than hexagonal shapes. I hollowed the honeycomb shapes, making room for cotton batting.
I put two layers of cotton batting and scraps in the honeycomb panels, closing them with living hinge tabs. My original plan was to put the shapes together, attach one side to the wall with 3M Command Strips, and secure the other end with a metal room divider holder. I executed my plan and it failed. The panels needed more support. I designed bottom and side brackets to help hold the panels together. I was surprised to discover that a partition with a height of 31.5″ did not require Command Strips to stand alone. The wall I designed; however, was 52.25″ high. Command Strips were still required.
Sound Assessment
Since the wall has been in place, it no longer sounds like people are standing next to me in my apartment’s convertible space when they are opening their door in the building’s hallway. This has increased my comfort and ability to relax. Purpose achieved!
Thoughts of possible future improvements usually enter my mind when a project is completed. After this project was done, I asked myself, “How can I achieve greater sound reduction with my model?” “How high can this partition go without becoming totally unstable?” “What is needed to make this wall stand without wall support?”
I was most curious about the first question as I wondered how many layers of cotton batting should be in the octagonal cavities. I found a research paper which suggested 8 layers of cotton batting to be a good number. The study investigated the sound absorption of nonwoven materials made from 100% cotton and 100% polylactic acid (PLA) fibers.
The key findings of the study were:
- Eight layers of cotton batts absorbed sound better than cotton fabric and PLA batts and fabric.
- Physical factors like fiber type, size, layering order, cross-section, thickness, density, airflow resistance, and porosity significantly affect sound absorption.
- Multi-layered absorbers performed better than single-layered absorbers of the same thickness.
- Cotton batts, in general, absorbed sound better than PLA batts.
- Webs (non-bonded) performed better than needle-punched fabrics in terms of sound absorption.
Model Files
The print files can be made available upon request in accordance with a Creative Commons Attribution-NonCommercial 4.0 International Public License. When using Cura, you will find that some of the parts need to be re-positioned for printing. I found it best to rotate the frames with the shorter side down and print with supports on the build platform only at 30% or more infill.
All of the honeycomb panels were printed with FormFutura Silk Gloss PLA White. It was on sale at 3D Printlife in October last year. I bought 4 spools and used approximately 3 1/2 spools to make 12 full and 10 half panels and backs; 1 full panel and half panel with hexagonal infill (iterations); more than 26 triangular connecters; and 56 hinge connecters (includes iterations). The pattern on the top panel was generated by PrusaSlicer as Concentric bottom fill pattern. I used PrusaSlicer for both of my machines to preserve dimensional accuracy.
FormFutura Silk Gloss PLA White flowed from the nozzle like liquid moonlight, solidifying into prints of shimmering, pearlescent white. Yes, the first sentence of this paragraph is an Ai rewrite, but it accurately describes my experience. The filament worked well on my MK3s+ and CR-10 mini. I used a 0.6 nozzle on the CR-10 mini which was modified with dual Z-axis, direct drive extruder, nylon/rubber timing belt, and borosilicate glass plate.
Frame parts were printed with Inland Matte White and Overture Matte White PLA with a 0.4 nozzle on the CR-10 mini. The frame requires assembly using 8 – M4*12 bolts and nuts,
This is a link to the cotton batting.