John Sayers' Recording Studio Design Forum Archive

Hey all! Just wanted to put my plans in text and see if there are any glaring holes or better practices I could employ so here is my situation and plan. I'm a voice actor, building a room in my walkout basement that is as soundproof as possible (especially from footfall on the above hardwood floors. All is unfinished at this point. I'm shooting for a noise floor in the room at or below -75dB at all times, so really stinking quiet. I can spend what needs to be spent to make it happen...just don't want to spin my wheels. This will be my fourth build of this nature in my own home (we've moved a lot).

I need to effectively block as much overhead footfall noise as possible and also lawn equipment and garage truck noise from outside. The ceiling of the basement is prefab joists. Ceiling is 9' so I have some room to work with and plan to build the inner room as a completely decoupled room, not using clips or hat track. I really want to figure out if I can add mass inside the joists and then build 2 free standing rooms in the basement (one inside the other). Or will that result in a triple leaf issue with the ceiling?

I ultimately planned for 2 layers of 5/8" drywall with green glue in the joist pockets, then 2x4 framed room with 3/4" plywood, green glue, 5/8" drywall then air gap then another identical room inside that with a floor with Delta-FL, rubber underlayment, then 2 layers of OSB with green glue finishing with carpet and pad inside the room. For doors I was planning on 2 thick solid core doors with no windows.

Or would it be better to treat the upper level floor as a sound source and just create a beefy 2 leaf fully decoupled room below it and add nothing above?

For ventilation, I just need to figure out a system that will circulate are as the rest of the basement will have a mini split system installed and even with it is 90 out (like it is today already) the basement stays around 75 or so with no HVAC at all.

Feel free to shoot holes in all my dreams and set me straight xD

Thanks for any assistance you can offer!

Greetings,

For ventilation, I just need to figure out a system that will circulate are as the rest of the basement will have a mini split system installed and even with it is 90 out (like it is today already) the basement stays around 75 or so with no HVAC at all.

Methinks an ERV is in order for ventilation. You're going to have your studio airtight, and no matter how cool it is, you need to breathe (passing out during a session reflects poorly on the "talent" ). Since you are going to install a mini split anyway, just go for a multi split (one outdoor unit with multiple air handlers). Controlling the humidity (you are in Raleigh after all), will be important and protect your gear.

All the best,

Paul

Would an ERV be better than just a simple low speed inlet and outlet fan running outside the room with a well built muffler type system to avoid cutting a hole in the otherwise isolated room? That was my plan. There is currently a dehumidifier running in the basement that I'm pretty sure the room design would completely mitigate. The fan is on the higher end of the frequency and it's not terribly loud.

I was just looking back at Rod's book and I think I found a picture of exactly what I need to do.

One question I still have with the design is will the footfall noise just run down the joists and basically around all the drywall placed up in the joist pockets? Is it really effective enough to add all the drywall to the bottom of the upstairs floor or would it be better to leave that alone and add two really thick decoupled layers below it?

Greetings once again,

Would an ERV be better than just a simple low speed inlet and outlet fan running outside the room with a well built muffler type system to avoid cutting a hole in the otherwise isolated room?

Yes. You need to exchange the air, not just circulate it. As much as we all want to will it to go away, there are at least three holes in the inner structure: the door, the air intake, and the air outlet. Minimizing the effect of those penetrations is the issue.

I was just looking back at Rod's book and I think I found a picture of exactly what I need to do.

Good.

I would check Rod's book concerning your other question.

All the best,

Paul

So I guess the specific question I have that I don't see really answered in the book is whether it is better to have a that floor left alone and then two thick decoupled structures below or better to beef up the floor and add a single structure below. I still need to create 2 structures below for the walls of that space, so I'm trying to figure out what is going to be best for isolation. I assume I don't want to attach the outer wall to the upper floor joists.

Any thoughts on that question?

I am not sure what the question is exactly. But I have seen a third layer dramatically reduce Transmission Loss. But have you considered treating the source floor from above? i.e. Install a resilient layer and a new damped mass floor above that. And, acoustically efficient Carpet with similar Underlay.

Thanks for the reply.

I am trying to determine what would actually constitute a third layer. If the basement is unfinished, would the upper floor act as a third layer or would it act more like a sound source since the airspace around the new room below is open?

It makes sense that adding 3 layers in a wall system would cause an issue, but if it is open, does that mean it wouldn't truly be a 3 leaf system?