Small drum room - existing masonry walls and concrete slab

Hello there everyone! First of all, I'd like to thank all the experts here for giving a little of their time and knowledge to help us out! Really, thank you! I live in São Paulo Brazil and I'm an amateur drummer. I have a (very) small spare room in my house I'd like to turn it into a drum, and maybe a 4 piece band practice room. The room dimensions are 3,32m x 1,97m x 2,5m (height). The walls sits over a 20cm concrete slab above the garage and are made of 15cm concrete blocks, and a 3cm layer of mortar on each side. Pretty traditional building method here in Br. The celling is also a concrete slab. Above the it there is a bedroom and behind one of the walls is a TV room. The nearest neighbor window is about 5 m away. The idea here is to have a place I can play drums and if possible have an occasional weekend band practice, without driving my neighbors mad. Hopefully bring the noise levels from 110dB to about 80db (or 70!!??)! Since the room is already very small and I don't want to spend too much money on a rental house, I think a proper two leaf, room in a room system is not an option here. And also I don't need a whole lot of sound attenuation. So my idea is to use the already high mass of the existing masonry wall and concrete slabs as sound attenuation. So my questions are: How much sound attenuation can I get with the existing walls, considering I properly build and install a heavy MDF door. Let's say 6cm thick? Something like this. And also do something similar to the window. Inside>1 layer MDF (or plasterboard) mounted to inside of window frame>insulation> 4 layers of MDF mounted to exterior of window frame. Also a silencer box to extract air. Air intake would be a 9.000BTU A/C unit. Would that work at all? Another possibility is to increase the mass even more by screwing plasterboards directly onto the walls. Would these layers of plasterboard add any attenuation at all or it's completely irrelevant? If so, how much attenuation could I get with that system? Hope to hear from you guys! Once again, thanks a lot!

I'm unable to give you a number here, but I have a few things to say: - set up your drums, buy a meter and get someone to go outside and measure how loud it is. From there, you know how well your current situation is working. - you've outright said that you won't do a two leaf system. That leaves you to 2 options. 1) seal it up the best you can and add mass 2) seal it up and use resilient channel and add mass. - RC is not good at isolating low frequencies. Those are the ones that are going to piss your neighbours off. It's failure rate is high and adds more headache and cost than it's probably worth. - Green glue can help a lot. You could add a few layers of drywall with green glue and probably improve your situation a fair bit. - You need a BEEEEEEFY window plug and door. - I don't fully follow your diagrams regarding ventilation. It's a major concern for sound leakage though. If this is a rental house and you don't want to spend lots of money and it's just for jamming, you might want to consider just circulating fresh air from within your home rather than risking your already poor isolation by tapping into the fresh air outside. I know this isn't ideal, but it might be the cheapest and most fool proof. Again, not ideal, but worth thinking about. Greg

Hey Greg! Thank you for your attention and help! So...

Gregwor wrote:

That leaves you to 2 options. 1) seal it up the best you can and add mass

That's the idea here. I know it's by far, not the ideal strategy. But it's what I can do for now giving all the conditions (budget, space, rented house). Maybe I should start with the door and window and go from there. Measure and see how bad it is. The door shouldn't be too hard to deal with. I'd make a beefy door out of MDF (about 2 1/2 inches) and seal it up well. My main concern and possibly the hardest to achieve would be sealing up the window. Here's a pic of how it is now. I'm thinking two layers of MDF on the inside, stuff it with insulation, and another 3 or 4 layers on the outside. Kindda like a two leaf system. I know it wouldn't work as such, but it'd be beefy (would it!??) and dense. I'd still want to figure out a way to add some kind of a baffle box to this window to remove the stale air. The air intake would be from a 9.000BTU A/C unit. Here's a idea, probably wrong, I know... Any ideas??

Gregwor wrote:

Green glue can help a lot. You could add a few layers of drywall with green glue and probably improve your situation a fair bit.

I know Green glue would be great, but it is hard to find here in Brazil and crazy expensive. So, you know... My question is... If I do all of that, measure, and it's still too loud, could I add mass by screwing the plasterboards to the wall (3 layers)? Would this added mass give any additional attenuation at all to these already heavy walls? Thanks again Greg!

Remember, each pane of glass counts as a leaf. Any more than 2 leafs = less isolation. For your silencer, you'd get the best results having 1 inside on your inner leaf and 1 outside on your outer leaf. Each with at least 3 baffles and built heavy. I'm not sure what kind of weather you get there, but MDF doesn't play well with moisture.

could I add mass by screwing the plasterboards to the wall (3 layers)? Would this added mass give any additional attenuation at all to these already heavy walls?

Certainly. But like I've said before, you wouldn't achieve leaps of improvement in doing so. I suppose, do the window and the door and take some measurements. At least then, you'll know what you're up against! Greg

I appreciate the help Greg! I'll do that and post the result here. Maybe someone else could have the same kind of issues and needs. Cheers!