If you don’t care much about compactness, you can easily make a DIY muffler: A long pipe with a sound absorber layer. Sound wave goes along the pipe. Its outer part gets absorbed and due to the diffraction inner part spreads. The impedance is exponential, or in decibells is proportional with respect to the length of the pipe.
Why not? If it has a good fun, the most of the noise will be airborn, and so you only need to attach mufflers to inlet and outlet. But perhaps there can be difficulties if you didn’t want to disasseble it.
I did for myself DIY purifier and used extremely noisy high-pitched 40mm fun for server units at 18000rpm. High frequencies even better get absorbed by the muffler. And due to the small size, these fans can produce high pressure at slow troughput. So can save on filter materials. Although didn’t finish it since activated charcoal I bought was of low quality. Using it in the kitchen only. If only I could insert pictures in the comment.
The filter moves a lot of air, so you need quite long pipes.
Speed matter only in the need for bigger pipe diameter. Impedance depend on the ratio of length to diameter.
You need pipes on both the input and output
Indeed.
Some of the noise will be vibration of the purifier body, so you might need to enclose that too
Depend on the quality of the fun bearing. Vibration of the air does transmit to the body and to the pipes, but very littlle. And if you can make an extra casing around, if you need.
This is how I was doing DIY purifier (first version of it) with a fun in the middle of pierced steel 60mm pipe. Wet charcoal on gauze wound around the pipe. Inside the pipe was a layer of reticulated polyurethane foam acting both as a filter and sound absorber. The thing afterwards put into 150mm pipe with a layer of polyurethane foam.
And that was quite quiet. The problem was in the quality of the charcoal giving a smell. So I reassembled it for better throughput and use in the kitchen without muffling.
And for the room I use this ugly and loud, but powerfull setup for short periods of cleaner air outside:
If you don’t care much about compactness, you can easily make a DIY muffler: A long pipe with a sound absorber layer. Sound wave goes along the pipe. Its outer part gets absorbed and due to the diffraction inner part spreads. The impedance is exponential, or in decibells is proportional with respect to the length of the pipe.
I wouldn’t expect that to work well for an air purifier?
Why not? If it has a good fun, the most of the noise will be airborn, and so you only need to attach mufflers to inlet and outlet. But perhaps there can be difficulties if you didn’t want to disasseble it.
I did for myself DIY purifier and used extremely noisy high-pitched 40mm fun for server units at 18000rpm. High frequencies even better get absorbed by the muffler. And due to the small size, these fans can produce high pressure at slow troughput. So can save on filter materials. Although didn’t finish it since activated charcoal I bought was of low quality. Using it in the kitchen only. If only I could insert pictures in the comment.
Problems I’d expect:
The filter moves a lot of air, so you need quite long pipes.
You need pipes on both the input and output
Some of the noise will be vibration of the purifier body, so you might need to enclose that too
Pictures on lesswrong do work, including in comments. Here’s one I inserted by using the WYSIWYG editor (“LessWrong Docs”) and pasting an image:
The filter moves a lot of air, so you need quite long pipes.
Speed matter only in the need for bigger pipe diameter. Impedance depend on the ratio of length to diameter.
You need pipes on both the input and output
Indeed.
Some of the noise will be vibration of the purifier body, so you might need to enclose that too
Depend on the quality of the fun bearing. Vibration of the air does transmit to the body and to the pipes, but very littlle. And if you can make an extra casing around, if you need.
This is how I was doing DIY purifier (first version of it) with a fun in the middle of pierced steel 60mm pipe. Wet charcoal on gauze wound around the pipe. Inside the pipe was a layer of reticulated polyurethane foam acting both as a filter and sound absorber. The thing afterwards put into 150mm pipe with a layer of polyurethane foam.
And that was quite quiet. The problem was in the quality of the charcoal giving a smell. So I reassembled it for better throughput and use in the kitchen without muffling.
And for the room I use this ugly and loud, but powerfull setup for short periods of cleaner air outside: