What is "MSM" or "MAM"?

[gullfo]

adding to this excellent input from Stuart - consider structural transfer as another critical element of isolation. if your walls and ceilings all have the proper mass and insulation, but the drums and amps are sitting on the floor and all the walls and ceiling parts are connected, then you're going to have a lot of sound energy going through the structure and those levels will be broadcast from adjoining surfaces. in many cases you cannot change your floor (e.g. a basement or garage) but you can decouple the walls and ceiling from the floor, and, you can use a decoupled platform for the drums kit, amps, etc to reduce the amount of energy going directly into the floor and into the structure.

also, the acoustic treatment in the room will reduce the levels of energy. absorption, either simple or via membranes, tortured path (ala broadband hangers, hardback clouds, etc) will reduce the energy impacting the room surfaces as well as overall levels in the room.

next up - if you're not creating a critical listening space (ala control room / mix room / mastering room etc) then room ratios are less important and in some cases, it can be helpful to have some different modal spaces (more gooder for very large rooms than small ones). that said, let's say you build the room to max out the volume within the exterior shell - you can use hard treatments to alter the room behaviour - esp if you add things like slats across corners, soffits (which not only provide a path to route the air flow ducts but massive absorption for a room in the upper wall-ceiling corners freeing up floor space), and clouds which provide waveguide functions to alter the floor-ceiling relationship.

[Billdog2025]

Amazing information thank you! For Drums ....I have an opportunity to purchase a pre-owned Whisper Room single wall, very large 7 x 9.
I know it won't be prevent bass drum, and loud snare drums from being heard outside of the room. Not even the double wall version is soundproof for drums. But the 7x9 space gives me enough real estate to build interior walls within the walls. And those interior extra walls will basically be freestanding, and uncoupled from the whisper room walls. This is far less costly (for me) than building the double wall structure from scratch. How can I get the ideal / highest STC for those extra walls ? Attached page 63 from Rod Gervais's book. What's the ideal construction for this inner room ? Most people would never add to a whisper room trying to improve it, but in this case, the Whisper room cost is cheap enough where it makes sense for me.

[gullfo]

the challenge with the whisper room approach - if the unit as complete partitions (meaning it has mass boundaries on each side of the "frame"), then adding a second wall you end up wih a structure similar to the 3rd up from the bottom of your picture. removing the inter-mediate mass so it's like the 5th from the bottom, is a 17 STC point increase simply by increase the air space between mass (remembering that air sucks as an acoustic energy transfer medium).
with the whisper room, i'm presuming you need to remove the outer mass boundary and on the new "external" wall, the inner mass boundary to maximize the air gap (the frame spacing need only be ~1" apart - it's the mass to mass distance that matters). for example 2 2x6 walls with a 1" gap = 12" of air space (5.5" x 2 + 1"), 2 2x4 walls = 8" of air gap (3.5" x 2 + 1"). lower density mineral wool (~36-42kg/3) and pink insulation (~28-32kg/m2) don't really count as "mass" per se (given drywall is about 2900-3000kg/m3), and so if there is contact between the two wall insulation, it doesn't hurt anything, and in most cases, a slight pressure ensures full contact with the mass boundaries.

[Billdog2025]

Thanks! I just hauled the pre-owned "Whisper room" panels into my garage today. Is actually just 1" MDF walls covered by thin fabric. Not really a wall structure at all, just thick and heavy 1 ply walls. definitely well finished, with hardware anchor points, and well built exterior baffle boxes for ventilation. By itself, it will probably achieve 30-35 DB reduction.

My plan is to add a separate inner framed wall, 2x4, with double 5/8" drywall and either:
1) leaving the outer side open and exposed to a 1" airgap to the Whisper wall, or
2) sealing that outer side wall with another 1 ply of 5/8" drywall, and maintaining 1" of air to the whisper wall, decoupled as best as possible.

Maybe option 2 yields more isolation of lower frequency. I'm trying to isolate those loud snare drum cracks that hit at 110 DB.
If I can get those into the 60 db range, project will be a success !

Thanks again for all your insight into the math.

[gullfo]

i would add another layer of 5/8" to the inside of the whisper wall panels and leave the gap, but plan on using decoupled isolation sway bracing to make sure the whisper walls are full stable. i.e. the attach to the 2x4 frame and the whisper wall @ about 3/4 of the way up the wall, and 48" o.c. see kinetics noise https://kineticsnoise.com/unibrace/isolation-bracket or mason industries

[Billdog2025]

OK! For building the Room inside a whisper room.... Ordering the materials this weekend. Just to confirm, you would go with double 5/8" drywall + insulation + single 5/8" drywall for the interior structure. Then Add more 5/8" Drywall directly onto the 1" MDF Whisper Room original wall ? And use decoupling brackets between the the Whisper wall, and that extra sheet of drywall ? So thats 2+1+1 = 4 Actually adding 4 sheets of drywall, carefully placed ? Seems logical. More mass / more isolation.

PS does Green Glue as a damping material help between the double drywall? It's not actually glue, so still need drywall screws holding it together. I've heard 1 layer of green glue, is about the same as 1 layer of drywall. But it takes up less space.