I thought I'd found the perfect space. I just wanted a room to record spoken voice but to have up to 6 people comfortably at a time. I wanted a neutral and dead space and found a fabulous asymmetrical basement in Santa Monica. I put a mic in the room and left it for five days - utter perfection. all I got was a sub from some big truck on the street that was no problem as it was so low and quiet that it would be inaudible on a close mic voice even without roll-off so I rented the space. I softened up the walls to dampen down high-end reflections with insulation in frames, and used curtains on one wall. the a/c was easy with a baffle. All sweet and recording in the space was great.
But then there was a refurb above and tiled floors and then high heels that cut into the space through the concrete and steel with acoustic precision, so we now have to stop while people walk. Hell. I need to isolate my room. I'm resigned to the fact that I need to build a room within the existing room. I just want to do it right and get the best STC as I possibly can.
I had a number of designers and builders come down to quote and as a result my confidence is low. I do know my way around basic acoustics and understand the impact of contact, air density and insulation but I've been bombarded with all sorts of 'solutions' and budgets from 7k to 50k and I'm a little lost right now. I just want to do the best I can and am currently seeking the bible of acoustics so I can weed out the weeds and get the job done as cost effectively as I can.
The floor is fabulous concrete. nothing significant comes through the floor but the ceiling and hollow walls amplify all that is above with precision.
I don't know how to upload photos here yet so I created a dropbox folder with photos and a pdf of measurements https://www.dropbox.com/sh/uqet53eece1n ... tSCxa?dl=0
I hope the URL isn't too long...
Keeping noise out
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Est
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Soundman2020
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Re: Keeping noise out
Hi there "Est", and Welcome! 
If that's not an option (or you can't persuade them to go for it), then you are stuck with "room-in-a-room" isolation, and a much larger bill.
It is no use at all for telling you how well your studio will be isolated. STC was never meant to measure such things. Here's an excerpt from the actual ASTM test procedure (E413) that explains the use of STC.
“These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television and similar sources of noise in offices and buildings. This classification method is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers, musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.”
It's a common misconception that you can use STC ratings to decide if a particular wall, window, door, or building material will be of any use in a studio. As you can see above, in the statement from the people who designed the STC rating system and the method for calculating it, STC is simply not applicable.
Here's how it works:
To determine the STC rating for a wall, door, window, or whatever, you start by measuring the actual transmission loss at 16 specific frequencies between 125 Hz and 4kHz. You do not measure anything above or below that range, and you do not measure anything in between those 16 points. Just those 16, and nothing else. Then you plot those 16 points on a graph, and do some fudging and nudging with the numbers and the curve, until it fits in below one of the standard STC curves. Then you read off the number of that specific curve, and that number is your STC rating. There is no relationship to real-world decibels: it is just the index number of the reference curve that is closest to your curve.
When you measure the isolation of a studio wall, you want to be sure that it is isolating ALL frequencies, across the entire spectrum from 20 Hz up to 20,000 Hz, not just 16 specific points that somebody chose 50 years ago, because he thought they were a good representation of human speech. STC does not take into account the bottom two and a half octaves of the musical spectrum (nothing below 125Hz), nor does it take into account the top two and a quarter octaves (nothing above 4k). Of the ten octaves that our hearing range covers, STC ignores five of them (or nearly five). So STC tells you nothing useful about how well a wall, door, ceiling, or window will work in a studio. The ONLY way to determine that, is by look at the Transmission Loss curve for it, or by estimating with a sound level meter set to "C" weighting (or even "Z"), and slow response, then measuring the levels on each side. That will give you a true indication of the number of decibels that the wall/door/window is blocking, across the full audible range.
Consider this: It is quite possible to have a door rated at STC-30 that does not provide even 20 decibels of actual isolation, and I can build you a ceiling rated at STC-20 that provides much better than 30 dB of isolation. There simply is no relationship between STC rating and the ability of a barrier to stop full-spectrum sound, such as music. Or stiletto footfalls on tile. STC was never designed for that, and cannot be used for that.
Then there's the issue of installation. You can buy a door that really does provide 40 dB of isolation, but unless you install it correctly, it will not provide that level! If you install it in a wall that provides only 20 dB, then the total isolation of that wall+door is 20 dB: isolation is only as good as the worst part. Even if you put a door rated at 90 dB in that wall, it would STILL only give you 20 dB. The total is only as good as the weakest part of the system.
So forget STC as a useful indicator, and just use the actual TL graphs to judge if a wall, door, window, floor, roof, or whatever will meet your needs.
END OF TEXT TO SKIP OVER IF YOU LOVE STC OR ALREADY KNOW NOT TO USE IT!
The trouble is: how do you figure out which is which? Which of those guys has an acoustically sound, economically feasible plan for YOUR situation?
OK, so let's star from the beginning, and walk through the process, so you can weed out the losers and whittle down the winners.
First, you need to determine how much isolation you need, in terms of decibels, and what frequencies you need it at. That's the starting point. To do that, you need to find out how loud that unacceptable sound is, and what frequencies it is occurring at. Then you need to decide how quiet you need things to be inside your studio, and across what frequency range, also measured in decibels. Subtract your "quiet" number from your "loud" number, and the answer is "How much isolation you need, in decibels".
That's the key. If you don't know that number, then you have no way of evaluating which of the options will do what you need it to do. You won't know which are "underkill" (not providing enough isolation), which are "overkill" (providing more than you need, which is fine, but it also means that you are paying more than you need to), and which are about right.
OK, so now you have a number in hand, and a bunch of proposals. Examine all of the proposals, and the ones that don't cleanly define how much isolation you will get, in decibels (not STC!) can go in the trash. Those are the scam artists, or the ones who don't know what they are doing, or the ones who do know but don't have enough confidence of guts to put it down on paper. You don't want those guys.
So now you have a lot fewer proposals, and hopefully some of them will have numbers that are in the region you are looking for.
Of those remaining, realistic proposals, toss the highest bid and the lowest bid. You don't want either of those.
That probably only leaves you one or two, which makes the rest of your job an awful lot easier! Now all you have to do, is to check what they are actually proposing to do, in terms of materials and dimensions, do the math, and confirm that the proposed structure will really accomplish what they claim it will.
That said, I did notice that you are going to have a problem with your door: The new inner-leaf is going to block off about a third of your existing doorway, so you will also need to move that existing doorway over by quite a bit. It might even be worth your while to block off that door completely, and make the window on that same wall into the door. That's probably what I would do, if I were designing that. It makes a lot of sense, acoustically and also economically. You are going to have to do major surgery on that existing wall anyway, so you might as well make the most of the opportunity to optimize things, which will simplify construction of the inner-leaf, and reduce your costs.
Another thing you said got y attention: "... and hollow walls amplify all that is above ...". If this is a studio, then why are the walls hollow and tuned to such a high frequency that they amplify structure-borne sound? That doesn't make much sense... Do you mean that the existing walls are simple stud walls with drywall on both sides? Or do you mean "hollow" in some other sense? If you mean what I think you mean (single studs with drywall), then you have a bigger task than you imagined ahead of you, as you'll need to deal with that extra leaf, to avoid ending up with three-leaf walls and ceiling, which could potentially make matters worse, not better. There are methods for dealing with that, but it's important to first understand the existing construction in order to check the design of the new construction, and make sure that you aren't setting yourself up for an unpleasant surprise...
- Stuart -
Right below the window area where you type your post, there's a section titled "Upload attachment". Click the "Browse" button next to where it says "Filename", select the file you want, hit "Add the file". You can add more files if you want, then hit the "Submit" button when you are done.I don't know how to upload photos here yet
Usually the easiest and cheapest method for dealing with that type of impact noise it to kill it at the source: approach the owners of that upstairs room, and offer to install the very best carpet money can buy in that room, at no cost to them. Finest, most beautiful, top quality carpet. You pay for it. No matter how much it costs, it will still be far cheaper than isolating your room.But then there was a refurb above and tiled floors and then high heels that cut into the space through the concrete and steel with acoustic precision,
If that's not an option (or you can't persuade them to go for it), then you are stuck with "room-in-a-room" isolation, and a much larger bill.
OK, but first of all, forget STC. It has no place in measuring isolation of acoustic spaces. It was never meant for that, and is actually pretty useless. Here's my usual long spiel about why you should never, ever, use STC numbers for figuring studio isolation: if you already know this stuff, then feel free to skip over it...I just want to do it right and get the best STC as I possibly can
It is no use at all for telling you how well your studio will be isolated. STC was never meant to measure such things. Here's an excerpt from the actual ASTM test procedure (E413) that explains the use of STC.
“These single-number ratings correlate in a general way with subjective impressions of sound transmission for speech, radio, television and similar sources of noise in offices and buildings. This classification method is not appropriate for sound sources with spectra significantly different from those sources listed above. Such sources include machinery, industrial processes, bowling alleys, power transformers, musical instruments, many music systems and transportation noises such as motor vehicles, aircraft and trains. For these sources, accurate assessment of sound transmission requires a detailed analysis in frequency bands.”
It's a common misconception that you can use STC ratings to decide if a particular wall, window, door, or building material will be of any use in a studio. As you can see above, in the statement from the people who designed the STC rating system and the method for calculating it, STC is simply not applicable.
Here's how it works:
To determine the STC rating for a wall, door, window, or whatever, you start by measuring the actual transmission loss at 16 specific frequencies between 125 Hz and 4kHz. You do not measure anything above or below that range, and you do not measure anything in between those 16 points. Just those 16, and nothing else. Then you plot those 16 points on a graph, and do some fudging and nudging with the numbers and the curve, until it fits in below one of the standard STC curves. Then you read off the number of that specific curve, and that number is your STC rating. There is no relationship to real-world decibels: it is just the index number of the reference curve that is closest to your curve.
When you measure the isolation of a studio wall, you want to be sure that it is isolating ALL frequencies, across the entire spectrum from 20 Hz up to 20,000 Hz, not just 16 specific points that somebody chose 50 years ago, because he thought they were a good representation of human speech. STC does not take into account the bottom two and a half octaves of the musical spectrum (nothing below 125Hz), nor does it take into account the top two and a quarter octaves (nothing above 4k). Of the ten octaves that our hearing range covers, STC ignores five of them (or nearly five). So STC tells you nothing useful about how well a wall, door, ceiling, or window will work in a studio. The ONLY way to determine that, is by look at the Transmission Loss curve for it, or by estimating with a sound level meter set to "C" weighting (or even "Z"), and slow response, then measuring the levels on each side. That will give you a true indication of the number of decibels that the wall/door/window is blocking, across the full audible range.
Consider this: It is quite possible to have a door rated at STC-30 that does not provide even 20 decibels of actual isolation, and I can build you a ceiling rated at STC-20 that provides much better than 30 dB of isolation. There simply is no relationship between STC rating and the ability of a barrier to stop full-spectrum sound, such as music. Or stiletto footfalls on tile. STC was never designed for that, and cannot be used for that.
Then there's the issue of installation. You can buy a door that really does provide 40 dB of isolation, but unless you install it correctly, it will not provide that level! If you install it in a wall that provides only 20 dB, then the total isolation of that wall+door is 20 dB: isolation is only as good as the worst part. Even if you put a door rated at 90 dB in that wall, it would STILL only give you 20 dB. The total is only as good as the weakest part of the system.
So forget STC as a useful indicator, and just use the actual TL graphs to judge if a wall, door, window, floor, roof, or whatever will meet your needs.
END OF TEXT TO SKIP OVER IF YOU LOVE STC OR ALREADY KNOW NOT TO USE IT!
So it seems you've found some scam artists, snake oil salesmen, and maybe one or two serious acoustic designers?I do know my way around basic acoustics and understand the impact of contact, air density and insulation but I've been bombarded with all sorts of 'solutions' and budgets from 7k to 50k and I'm a little lost right now.
The trouble is: how do you figure out which is which? Which of those guys has an acoustically sound, economically feasible plan for YOUR situation?OK, so let's star from the beginning, and walk through the process, so you can weed out the losers and whittle down the winners.
First, you need to determine how much isolation you need, in terms of decibels, and what frequencies you need it at. That's the starting point. To do that, you need to find out how loud that unacceptable sound is, and what frequencies it is occurring at. Then you need to decide how quiet you need things to be inside your studio, and across what frequency range, also measured in decibels. Subtract your "quiet" number from your "loud" number, and the answer is "How much isolation you need, in decibels".
That's the key. If you don't know that number, then you have no way of evaluating which of the options will do what you need it to do. You won't know which are "underkill" (not providing enough isolation), which are "overkill" (providing more than you need, which is fine, but it also means that you are paying more than you need to), and which are about right.
OK, so now you have a number in hand, and a bunch of proposals. Examine all of the proposals, and the ones that don't cleanly define how much isolation you will get, in decibels (not STC!) can go in the trash. Those are the scam artists, or the ones who don't know what they are doing, or the ones who do know but don't have enough confidence of guts to put it down on paper. You don't want those guys.
So now you have a lot fewer proposals, and hopefully some of them will have numbers that are in the region you are looking for.
Of those remaining, realistic proposals, toss the highest bid and the lowest bid. You don't want either of those.
That probably only leaves you one or two, which makes the rest of your job an awful lot easier! Now all you have to do, is to check what they are actually proposing to do, in terms of materials and dimensions, do the math, and confirm that the proposed structure will really accomplish what they claim it will.
That said, I did notice that you are going to have a problem with your door: The new inner-leaf is going to block off about a third of your existing doorway, so you will also need to move that existing doorway over by quite a bit. It might even be worth your while to block off that door completely, and make the window on that same wall into the door. That's probably what I would do, if I were designing that. It makes a lot of sense, acoustically and also economically. You are going to have to do major surgery on that existing wall anyway, so you might as well make the most of the opportunity to optimize things, which will simplify construction of the inner-leaf, and reduce your costs.
Another thing you said got y attention: "... and hollow walls amplify all that is above ...". If this is a studio, then why are the walls hollow and tuned to such a high frequency that they amplify structure-borne sound? That doesn't make much sense... Do you mean that the existing walls are simple stud walls with drywall on both sides? Or do you mean "hollow" in some other sense? If you mean what I think you mean (single studs with drywall), then you have a bigger task than you imagined ahead of you, as you'll need to deal with that extra leaf, to avoid ending up with three-leaf walls and ceiling, which could potentially make matters worse, not better. There are methods for dealing with that, but it's important to first understand the existing construction in order to check the design of the new construction, and make sure that you aren't setting yourself up for an unpleasant surprise...
- Stuart -