Part 2 of 5 - Building the sound proof enclosure for my air compressor

The plan for the enclosure will be a box without the bottom panel. There will be 1 door on one side for easy access to the compressor when draining it and a lid on top. The compressor will be resting on the concrete floor, as I would think that if it was resting on the enclosure might create more noise due to reverberation and vibration. Making the box is one thing, now we have to design into the enclosure a mechanism for cool air to ventilate inside and the warm air to be let out ensuring the compressor does not overheat as it cycles. All the while keeping noise inside. The lid on top of the enclosure is where the output baffle will be situated. The input baffle is located opposite the side of the door.

Making input and output sound baffles

I have done a bit of research and found several ways to enable ventilation and soundproofing at the same time, and eventually decided that the easiest is to build input and output baffles using the labyrinth method. This is essentially a muffler design which works because sound waves do not like to go around bends, but this is fine for air to travel through. Basically the more bends the better. Shown in the photo is the input baffle/muffler where the inside surface is lined with some noise absorbing foam.


I could have been more liberal with the foam but I ran out. You can also see the round hole I created for the cooling fan. For the fan I used a 240V AC cooling fan. The model I got is a 105 cfm capacity which I got from Jaycar Electronics. This enables the air inside the enclosure to be replaced 5 times every minute, ensuring more than adequate ventilation. The fan is connected so that it pulls air into the enclosure and forces air out through the output muffler. The output muffler is very similar in design to the input baffle, but this doesn't have a cooling fan installed. Just a hole on each end of the muffler. Next photo shows the output muffler with the rectangular airway.


The input and output baffles will now be attached to the enclosure from the inside. I used small angle brackets for these. The next photo shows a hole on the outside of the enclosure. This hole is for the input baffle. So the air will be sucked through this hole, through the labyrinth inside the input baffle, through the fan, then into the enclosure. As there is no other way for the air to go, it then goes out through the output baffle, which is located in the lid on the top panel. I have tested this and it works really well, ventilation-wise that is. I can't wait to see if the sound deadening actually works...

Part 1 of 5 - Building the sound proof enclosure for my air compressor

As I mentioned in my previous post, I am building a sound proof enclosure for my new electric Pilot Trademaster TM12 air compressor. I don't have access to a sound meter, but this thing is loud. I would just estimate it to be around 80db. When the motor kicks in, I cannot hold a conversation without raising my voice considerably. A consolation is that when this happens, it only takes about 45 seconds for it to fill the 58 litre air receiver. My goal in this exercise is to reduce the sound output so that first, I do not disturb my neighbors as I make my frames at night, and second, I don't crap my pants when the motor kicks in.

First of all, I will give you a bit of a background about where this compressor lives so that you will appreciate my reason of making the effort to build this enclosure. As you know I have converted my garage as my framing workshop. It is a 2 and a half car garage, and my workshop takes up 1 and half area, so that I only have space for 1 car. So yu can imagine that with the compressor being in a confined space as this, and with the metal garage door that echoes like crazy, the noise is amplified such that it makes so much disturbance, not only to me but most importantly to my neighbours. As a test, I tried standing outside my garage door while the compressor motor is running, and even with the garage door shut, it is quite loud and unacceptable if you ask me.

Making the basic enclosure

The first step in this project is building the base enclosure using 18mm MDF (medium density fibreboard). MDF sheets in Australia come in different thicknesses. The thickest being 36mm, then 25mm, then 18mm, 16mm and so forth. In terms blocking noise, the thicker the better. I'd like to use the 25 or 36mm but these were too heavy. I thought it would be very hard for me to build the enclosure by myself. I decided on using the 18mm sheets, as it is still thick enough for my purpose. I have read somewhere that 16mm MDF sheets have an STC rating of 29. Sound Transmission Class (STC) is the measure of the sound blocking property of a "wall", such that a STC 30 material typically reduces the decibel rating of the noise by 30 db, STC 20 by 20 db and so forth.

In building the base enclosure, I went the easy way and went to Mr Ply & Wood, a sheet material supplier in Australia. Gave them the measurements of the panels basing from my drawing plans. They then find the optimum sheet size that will fit it with the minimum of wastage, plus a small cutting charge. The result is professionally cut MDF sheets, that will all fit in my car and ready to assemble. In addition to the MDF sheets, I also needed 70mmx35mm structural pine timber which serves as the skeleton for the enclosure.

The following photos show the construction of the enclosure using the MDF sheets and pine timber.