how would you design an enclosure to isolate noise from a small electric motor? - Page 1
Forum section: electronics / general

author: engineheat
author_rank: Frequent Contributor
timestamp: July 17, 2019, 03:46:06 am
content: Hi,I got an application that uses a small dc motor. I've already tried lots of DC motors and even stepper motor, and experimented with PWM and so forth. I got it to the point where it's pretty quiet while still satisfying my need, and I don't think I can get it any more quiet.But it still has a slight audible sound if the room is quiet. I want to know if I can design the enclosure in such a way to further silence it, perhaps by using certain type of material? The goal is to put the motor inside the enclosure so that what little motor noise remaining is no longer audible from the outside.any advice would be helpful.thanks

author: bob91343
author_rank: Super Contributor
timestamp: July 17, 2019, 04:54:28 am
content: Just put it in a padded box. The thicker the padding, the more reduction in noise you get. If the noise is low frequency you probably need soft padding. Foam rubber or polyester foam.The way the motor is mounted is important. Isolation mounts will help. Don't use metal screws.

author: ogden
author_rank: Super Contributor
timestamp: July 17, 2019, 05:01:03 am
content: Low-RPM brushless (BDLC) motors are nearly noiseless. Such need ESC and something for speed control like Arduino, but could be cheaper solution anyway (than heavy-duty enclosure).

author: engineheat
author_rank: Frequent Contributor
timestamp: August 05, 2019, 02:12:41 pm
content: Quote from: bob91343 on July 17, 2019, 04:54:28 amHi, I need the box to block at least 40 dB of sound. The size can be as large as a shoebox. I'm thinking about using a plastic box as a frame, and then pad 2 layers of Dynamat (one layer on the inside, another on outside). And then I want to add 2 layers of foam padding, on top of the Dynamat.Similar thing would be done on the flat surface that the box would be place on, so all 6 sides would have 2 layers of Dynamat, and 2 layers of foam. Do you think 40 db is possible?I'm just not sure about using plastic box as the frame. A webpage I looked at recommended particle boards but those are too heavy for the application.Thanks

author: Nominal Animal
author_rank: Super Contributor
timestamp: August 05, 2019, 03:11:27 pm
content: Depending on the noise characteristics, you can get better results with multiple layers of different density foams, compared to a single layer of similar thickness. If you can add weight (as a plate) to a middle layer, it can help with the vibration.Personally, I'd just go for a quieter motor.

author: Benta
author_rank: Super Contributor
timestamp: August 05, 2019, 04:39:41 pm
content: Sandwich construction with fine sand in the middle. It'll be heavy, though.

author: bob91343
author_rank: Super Contributor
timestamp: August 05, 2019, 05:01:58 pm
content: Sometimes it's better to use open space rather than foam. And mount the motor with velcro or similar. Perhaps a better motor that has more attention paid to balance. Or redesign to operate at slower rpm.I worked at a company that made shake tables using air bearings.