Acoustical Steel Doors

Do you wish to experiment?

Well, one place to start might be people who are well versed in sound attenuation. United States Gypsum has many materials intended for this. Review this document for some general ideas, in particular the MiCore 160 and 300 panels.

In review of the document, you will see that sound attenuation is considerably more than packing insulation into a void, it is a series of solutions, each contributing to the overall rating of the sound assembly.

Hell, you can fill the void in a 6" steel stud wall with crunched up beer cans and achieve an improved STC rating. Caulk the perimeter, improve rating a little. Add RC1 channel one side, it improves a little more. It works the same for a hole in the sound rated wall that you need to fit with a door.

Thank you...

The problem is that you have two drum surfaces with air between them for the door. If there are plates separating the door into smaller cavities you have a problem filling the voids.

The easiest material to use is sand. It needs to be a good quality of sand and it must be oven dried to get rid of all the moisture. The downside is that the door will be very heavy, but it will be incredibly acoustically inert.

There are products that can be applied to the exterior of the door that may serve better and are much lighter..

Damplifier Pro is one such product. It is self stick and if applied to both sides of the door I would expect significant reduction in sound transmission and a much simpler installation than trying to fill the inside of the door cavity.

Antiphon Type A-13 is another commercial product used in automobiles to dampen sound.

EAR Type CN-12 is a graphite filled vinyl product used in submarines that is 1/4" or less in thickness.

These types of products all work in the same fashion by dampening the acoustic wave energy as the door skin vibrates. You may need to apply a second skin over the material to protect it and provide an esthetic finish. The manufacture should be able to provide recommendations for your application.

However, all the damping in the wold will not help if you do not gasket the door frame and the bottom door plate!

have you considered using expanding foam insulation?

Engineering Acoustics/Sound Absorbing Structures and Materials ...
Sound isn't easy to tame. Mass and distance are your best friends. You can't use distance so you'll need to make the sound work to get through the door. Somehow, acoustically disconnecting the two surfaces from each other will help

Convoluted foam has been used with some success. Metal is a poor choice for skin of a "soundproof" door.

Most of this is proprietary, but you might get some help from civil engineering departments of colleges.

Thanks for the advice!

As has been mentioned, steel is a poor choice for sound dampening. But if security and strength are an issue then it's a great choice. If you are attempting to keep a sound inside a building , then surface treat the inside, if you're trying to keep sound out then the outerside gets preference. Then maximize the interior space of the door with whatever filler is practical and affordable. But if you do not reduce the exterior surface excitation, then the filler alone will not be as effective. One other thing you haven't mentioned is the type and frequency of the sound you are trying to filter or block. Lower frequencies are very hard to reduce since the door's general shape and size easily become resonant requiring more physical dampening around the frame and closures. And try to dampen the entire interior space of the room (if it's the source area) to reduce the overall acoustic amplitude. Also remember that as you add something to the interior of the door, such as the aforementioned sand, the weight of the door will be enormous, so be sure and use properly installed and reinforced steel framing and hinges. Some buildings are just not framed to accept such a heavy door and will sag all too soon creating annoying troubles closing and opening. But then the steel framing will also be an added resonant member. Always trade offs. Good luck.

If this is for an interior door you might look at a fiberglass door with extreme gasketing for seal and sound attenuation. We have used these doors in industrial cold storage to -40 degrees. One of the benefits to using these doors is sound deadening as well as temperature extremes don't transfer as well as they are designed to fit anywhere a standard door installation is required it would save a lot over custom design or you might build on the fiberglass design.When we have used these doors they are right next to large interstate exit ramps for the trucks to get off and on quickly. With that in mind you have a lot of exhaust breaking and heavy acceleration from these large trucks. When we are inside these doors we don't notice any of the outside noise at all, almost total sound deadening. It might be a good place to start I don't know the numbers for these type of doors as well as Doorman, he might be able to provide you with some more info on these type of doors as I only do security installs on these type of doors such as locks and access control. Duke

One material does not work best. layers of materials with different densities pore sizes will attenuate sound over a greater frequency range.

Are you just producing the door slab? At these levels of attenuation the door seals and frame become an issue.

Thanks for your response. We are manufacturing only the door and the frame which we sell through a network of distributors. We will purchase the seals from a company in our industry that has had their seal sets tested and certified for the aforementioned STC ratings. The frame cavities are typically filled with grout and from all of my research within our industry, the frame is not a big deal. My main focus at this point is figuring out exactly what to put inside the doors...I was hoping to find someone with direct experience that could point me in the right direction. Layering is apparently how most manufacturers are building these doors...most steel door manufacturers use some form of offset steel stiffeners as the "base core" in order to keep the door from "pillowing" when the insulation/sound deadening materials are installed.