Home appliances sometimes create a lot of noise. This happens when we run them, or perhaps when they run themselves. This can be quite annoying.
Let's soundproof a dishwasher: We'll do this in a series of steps, each accomplishing a higher level of dishwasher sound reduction. This means we may need full access to all parts of the unit and it makes a difference as to whether it's a counter model or a stand alone cabinet type.
Step 1) The quickest noise control can be had without full access by just removing the front door cover. This is usually done by taking out 2 screws at the bottom of the door and lifting out the front panel. These panels are made easily removable in order to quickly change the color of the unit to match the kitchen decor.
You will usually find a piece of foam material floating loose about in the space between the inner door and the removed outside panel. It is worthless for our sound control purpose and may be discarded. Measure the depth of the space and cut a piece of "Super Soundproofing" absorbent mat of the same thickness or slightly thinner to fit into this space. Fit it right to the edge of the door, attach securely with contact cement to the inside of the washer, making sure you cover the entire area. Now replace the panel and the screws.
Step 2) Under the door will usually be another, shorter panel held in place in the same way. This will have (maybe) about a 2" thick fiberglass batting attached to it. Remove and discard this useless material. Cut a piece of 2" thick "Super Soundproofing " absorbent mat and glue intro place. (Thin thicknesses of foam can be glued together to make thicker thicknesses). Note that you haven't blocked any of the cooling vents, just replaced the batting. Put that small cover panel back.
Step 3) Now we need access to the dish washer unit, so pull it out of the counter or remove it's case so we can drape soundproofing mass loaded vinyl (we call it "Floor mat") over the unit. Cut a panel of it so that it goes from the floor on one side, up and over the unit to the floor on the other side. Don't worry about the back of the machine, nor does it need to be attached. Lay it over any insulation that may be on the unit. The material will be in the form of an upside-down "U". A dab of "Goop" (a household adhesive from the hardware store) here and there will hold it place.
Step 4) Line the dishwasher cabinet or the counter it fits into with 1/2 " "Super Soundproofing" absorbent mat attached with contact cement to provide an absorbent compartment for the unit to fit into and slide it back into place. Try to make sure the foam covers the entire area, without gaps. Use a thickness appropriate to the space.
Step 5) Check the fit between the unit and it's cabinet or counter, if it's more than 1/2", place a piece of wood molding along the edge with a strip of the soundproofing mat attached to it to provide a tight seal, thereby blocking sound from coming out around the gap of the washer and the counter cabinet.
One might be tempted to wrap the motor with soundproofing as motors might seem to make a lot of noise. But these motors operate near the limit of their ratings and are generally of the open frame variety because of much needed cooling. Thus it is not recommended nor necessary as much of the noise created is from the water washing cycles and we will have dealt with that very well!