SOUND ON SOUND

[jmch]

Can anyone recommend how I can push this door tight without obstructing emergency access from the outside?

In my current studio I just rely on the pressure exerted by the door closers. However, in my last studio I had magnetic sealing strips all around the door (a bit like fridge seals).

Then there's the issue of covering gaps (sides, top and bottom) between this inner door and the solid composite door that's going on the outside leaf. This door comes with its own frame and airtight seals.
...

Can anyone suggest any other method of closing these gaps?

As long as you don't couple the two leaves together you can use whatever you like. I've just wedged some spare acoustic foam in the gap between the control room and booth while I deliberately widened the gap between the outer and inner entrance doors to allow me to put a computer in there.

Thanks for the suggestions James.

I've put a link to some photos of the inner door frame so far, that also show the gap I'm talking about.

https://imgur.com/a/oCpCRpw

John

[jmch]

Yes, rounded corners everywhere if you can, although the entrance to the baffle box should be arranged like this:



Not as you had it in the diagram:



...as that first inlet area would be practically useless and the baffle box would effectively start at the gap between the first baffle and the casing, so you'd be wasting space, wasting material and losing some attenuation.

Wonks, I've redesigned my silencer box as here:
https://imgur.com/vv95k5m

As I said before, I'm going with the two internal ones first (one for the exhaust and the other for the air in) on opposite sides of the room. There won't be space for any more inside the room. If necessary I can have another one outside for the passive inlet, but it'd be more problematic for the exhaust given the exterior fan I'm using :
https://imgur.com/ZgUG6gJ
This fan is recommended for studios where the aim is to keep fan noise outside.

The company who supplied the fan advised 8-10m ductwork max, so I'm a little concerned about adding too much extra 'length' in the silencer boxes. Currently there are two 10m ducts snaked in the now inaccessible roof cavity. I've told my builder he'll need to pull some ducting out through the exterior holes that will be bored, and shorten the length, to allow for the silencer boxes. Am I correct in viewing the area in the silencer boxes as extra length for the fan (and passive air in) to travel through?

Finally, I want to put some fine mesh in to prevent insects getting in. The fan company suggested this and said it shouldn't affect air flow significantly on this fan as long as this mesh is at the fan end:
https://imgur.com/JYYxvxB
My builder has suggested putting it inside the fan unit just behind the vents. And likewise on the passive inlet vent.
Any thoughts here?

Thanks

John

[Wonks]

That silencer design looks better. I don't know how close to ideal it, as until recently I designed HVAC controls systems and have picked up a lot of mechanical and electrical knowledge along the way. So I generally know what's wrong and right, and know some of the details but not all of them.

The maximum ducting length stated will be based on the pressure drop of the ducting at the nominal fan volume. The bigger the ductwork, the lower the pressure drop for the same flow rate. The baffle box has a larger cross-sectional area than the ducting from it (and so lowering the pressure drop), but it also has those 180° bends (increasing its pressure drop).

So you could probably allow its pressure drop across its length (not the total of the air path through it) to be that of the ducting.

The mesh should be OK. Ideally you'd fit it in an external grille that's bigger than the ducting to reduce the air velocity across it to both reduce the pressure drop across it and also reduce any noise it might generate.

Also note that if it does its job, the mesh will start to get blocked with insects, reducing airflow and slightly increasing any noise created by the mesh. So I'd make it easily removable for cleaning, and maybe have two meshes so that you can swap over and clean the dirty one at your leisure.

[jmch]

That silencer design looks better. I don't know how close to ideal it, as until recently I designed HVAC controls systems and have picked up a lot of mechanical and electrical knowledge along the way. So I generally know what's wrong and right, and know some of the details but not all of them.

The maximum ducting length stated will be based on the pressure drop of the ducting at the nominal fan volume. The bigger the ductwork, the lower the pressure drop for the same flow rate. The baffle box has a larger cross-sectional area than the ducting from it (and so lowering the pressure drop), but it also has those 180° bends (increasing its pressure drop).

So you could probably allow its pressure drop across its length (not the total of the air path through it) to be that of the ducting.

The mesh should be OK. Ideally you'd fit it in an external grille that's bigger than the ducting to reduce the air velocity across it to both reduce the pressure drop across it and also reduce any noise it might generate.

Also note that if it does its job, the mesh will start to get blocked with insects, reducing airflow and slightly increasing any noise created by the mesh. So I'd make it easily removable for cleaning, and maybe have two meshes so that you can swap over and clean the dirty one at your leisure.

Thanks again for your good points Wonks :thumbup:

[jmch]

Guys

I've agreed with my builder that the top and one side of my boxes will be the inner ceiling and wall, which is made up of 2 layers of fire board with green glue between, a layer of 18mm OSB, and 100mm RW3 insulation behind.

So it will be the front side, bottom and end sides that are made and secured to the wall and ceiling, then caulked. These will be made of MDF with 2 layers of fire board green glued together.

See drawing here:

https://imgur.com/a/z5wUmzY

What's the view on doing this?

Thanks

John