5 simple questions about reducing sound dispersion

[kasmira]

Originally Posted by Heath01

6-- Will having a layer of cardboard covering the floor lessen significantly the amount of noise my downstairs neighbour will be hearing when the angle grinder is being used?

No, not at all.

Don't know enough to answer your other questions, sorry.

[jwl]

Originally Posted by Heath01

1---As there are 12" of hollow space between the original ceiling and and drop ceiling ---will I be reducing the sound that leaves the room through the ceiling by filling the empty space with fiberglass insulation? What I want to know is if I will be reducing it substancially.

Probably 3-6dB, all else being equal. Enough to notice a reduction in volume, but you certainly won't get rid of the sound.

Originally Posted by Heath01

2---As I have a solid plywood door that is only 2" thick ---what could I do to it to keep the noise of the grinder to travel outside through the door?

3--- I have a double glazed window with an aluminum frame. The frame is hollow so I'm thinking about drilling some holes into the frame so I can fill it in with "great stuff" insulation foam in spray. Will the frame do a better job at keeping the noise from travelling through it after I do it?

4--- As my double glazed window is not doing a very good job keeping the noise of the edge grinder from being heard outside the room I'm thinking about putting a plug on it every time the angel grinder is being used.

5-- Being that I won't be needing the light coming through the window once I put the plug, it occurred to me that it is't necessary for the plug to made out of glass. So I'd like to know what material should be used for it to be most effective in keeping the noise in. I'm guessing the only reason why a plug is always made out of glass is so it will possible to see through it and allow the light to come in but if I don't need for the plug to be transparent perhaps there are opaque materials that would be a better choice than glass. If this is the case which materials are these?

The answer to all of the above questions is to add mass to all surfaces, and make the room airtight (if air can get out so can sound). Once you've done that, there will likely be some flanking paths where sound can travel through the structure itself, you will need to identify these paths and problem-solve at that point.

Soundproofing is a very complex science. Adding mass and/or insulation will likely improve things, but all comprehensive solutions will require significant construction in all likelihood.

Originally Posted by Heath01

6-- Will having a layer of cardboard covering the floor lessen significantly the amount of noise my downstairs neighbour will be hearing when the angle grinder is being used?

Doubtful. I don't want to say no freakin way but I'd be astonished if cardboard had much effect on sound transmission from a grinder.

[Rod Gervais]

Originally Posted by Heath01

1---As there are 12" of hollow space between the original ceiling and and drop ceiling ---will I be reducing the sound that leaves the room through the ceiling by filling the empty space with fiberglass insulation? What I want to know is if I will be reducing it substancially.

Not anything I would consider substantial - perhaps 3dB - maybe a wee bit more

One problem we have here in really helping you is a lack of understanding about what you need to deal with - sound levels inside of the space when you are using the grinder - levels outside of the space also....

Is this a house or a apartment?

If a house - are you in the house or is this a shed on the property?

If a house - where is your space in relation to the house layout?

Where is your space in relation to the neighbors?

What is the existing construction?

2---As I have a solid plywood door that is only 2" thick ---what could I do to it to keep the noise of the grinder to travel outside through the door?

Single panels with a lot of mass can do a pretty decent job of aiding in low frequency isolation - not so good a higher frequencies.... which is what I would imagine you are dealing with then grinding steel (or other metals)

While doing a round of testing for the GG company Brian Ravnaas had an opportunity to do some testing of the effect of fiberglass isolation on single panel assemblies - which showed a fairly decent increase in the TL values of higher frequencies - with a slight drop in TL for lower frequencies.....

Facing the door with a rigid fiberglass (or other) panel in the area of 3pcf will aid in this regard - of course the largest single improvement would begin with properly gasketing the door to stop the free passage of air.

3--- I have a double glazed window with an aluminum frame. The frame is hollow so I'm thinking about drilling some holes into the frame so I can fill it in with "great stuff" insulation foam in spray. Will the frame do a better job at keeping the noise from traveling through it after I do it?

Don't expect much from this........

4--- As my double glazed window is not doing a very good job keeping the noise of the edge grinder from being heard outside the room I'm thinking about putting a plug on it every time the angel grinder is being used.

Good idea

5-- Being that I won't be needing the light coming through the window once I put the plug, it occurred to me that it is't necessary for the plug to made out of glass. So I'd like to know what material should be used for it to be most effective in keeping the noise in. I'm guessing the only reason why a plug is always made out of glass is so it will possible to see through it and allow the light to come in but if I don't need for the plug to be transparent perhaps there are opaque materials that would be a better choice than glass. If this is the case which materials are these?

Plugs are not always made out of glass - don't know where you got that idea....

You could make a removable plug out of a wood frame covered with multiple layers of drywall - filling the cavity with some fluffy insulation would help - as with everything else - edge seals would be important (where air can go so goes sound)

6-- Will having a layer of cardboard covering the floor lessen significantly the amount of noise my downstairs neighbour will be hearing when the angle grinder is being used?

Doubt if you would see any real measurable increase in isolation with this - but you would introduce on hell of a fire hazard - doubt if this is what you want to attempt when throwing all those sparks while grinding (not to mention welding)

Rod

[Heath01]

Many thanks to you Rod and jwl,

You've been very generous with your advise and it is highly appreciated.

Rod--- I just discovered you're a published author of a book dealing with these issues, so I'm honoured that you've taken the time to help me. The noise level inside my workshop is not a problem. My only concern is the noise level outside while I'm using the grinder.

My workshop is in an apartment building in NYC and my window faces the airshaft which is square shaped and has cement walls. Unfortunately is a perfect sound chamber, so much so if I open the window I can hear my neighbours talking very clearly. Imagine what it must be for them to hear me grinding metal!

After reading your replies I have a much better sense as to how to proceed so thanks again for all your help.

Since adding mass to my plywood door is the way to go, what material should I use? The same question applies to the window plug.

Question 1--- I'm thinking about screwing a sheet of PDB2 on each side of a sheet of plywood so what I will be screwing to my plywood door will be 1 sheet of PDB2 + 1 sheet of plywood + 1 sheet of sheetrock. The plug could also be a PDB2+plywood+sheetrock sandwich, and if it is a good idea I could leave a 1" air gap in between each of the three sheets.

---Would this three-layer sandwich do the job?

As the metal pieces I have to grind are sometimes fairly small in size it occurred to me the idea of building a cabinet similar to a "sandblasting cabinet".

sandblasting cabinet - Google Search

so the noise I'm making with the grinder will have an additional barrier to go through before hitting the walls, ceiling, and floor.

Question 2--- What would be the best soundproofing materials to use on the six walls of the cabinet? The shell will have to be plywood but I can make the walls as thick as I wish and I can screw any material on the inner and outer sides.

Question 3--- As the cabinet isn't very large in size it isn't very costly to add thickness to the walls and using different materials such as rubber. The same kind of rubber used on the mat of a weight-lifting room. But what should the formula be? rubber+sheetrock+plywood with a 2" air gap in between???

I found a great variety of soundproofing materials on this link:

PDB2 - Google search

so I'm a bit confused with so many sound-blocking products to choose from.

Question 4--- As far as the window frame is concerned... It surprises me knowing the aluminum structure of a double glazed window has nothing but air inside. Doesn't the air allow sound to pass through it thus counteracting the soundproofing effect of the double glass?

Would using a thick coat of rubber paint on the aluminum frame make it less difficult for sound to pass through it?

I look forward to your reply. Hopefully other readers will put in their two cents as well...

Heath