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PostPosted: Sat Mar 16, 2019 3:22 am 
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I want to record real instruments, that's the whole intention! But when drums are not realistic, I can live with this. And, as you say, recording drums elsewhere isn't that bad. Can be quite interesting.

The outside walls are part brick part wood. So the plan is: 5/8 MDF on outside outer wall + 5/8 on inside of outer wall -- 1x2 wooden studs with rockwool -- 5 cm air gap -- 1x2 wooden studs with rockwool -- 5/8 gypsum + green glue + 1/2 gypsum

HVAC above the roof of the inner room --> pointed roof.

Is it all right to put MDF on the outside of the outer wall and gypsym on the inside of the outer wall? As regards to possible resonance or so...

What I'm going to do now: simulate a few realities and check how much dB they produce --> 1. drum + guitar + bass loud; 2. drum + guitar + mellow; 3. Guitar amp and bass amp + listening to a mix (in turn, not together). Then I'll have to check how much the sounds degrades, from the studio till the point where people can be, with the inverse-square law. Then I can me a few scenario's, with help from the calculator, and see what is possible and realistic.


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PostPosted: Tue Mar 26, 2019 3:56 am 
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We want to measure the db output we produce with drums + bass + guitar. What's the best way to do this? I guess if you're in another room, it will be a bit different. And do we need to use a certain microphone setting + a special program? Or is an app on a phone also enough?


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PostPosted: Tue Mar 26, 2019 4:33 am 
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Is it all right to put MDF on the outside of the outer wall and gypsym on the inside of the outer wall?

MDF soaks up moisture and basically becomes soggy cardboard. You'll want to use 3/4" OSB for sheathing the outside of your building. Depending on how close it is to neighboring buildings, you might need to use fire treated OSB.

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We want to measure the db output we produce with drums + bass + guitar. What's the best way to do this? I guess if you're in another room, it will be a bit different. And do we need to use a certain microphone setting + a special program? Or is an app on a phone also enough?

Buy an SPL meter. I'm sure a cheap (like $80) one from your local music store would be fine. Just don't get a $20 one. And we have yet to find a phone app that is accurate without needing to be calibrated, so don't use a phone app. If you can find a link to one you're considering, please post it here so that we can check if it's decent or not. You'll want to set your SPL meter to SLOW and C WEIGHTING.
Attachment:
A vs C Weighted SPL.png

Greg


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PostPosted: Tue Mar 26, 2019 7:13 pm 
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You'll want to use 3/4" OSB for sheathing the outside of your building....


Noted!!


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Buy an SPL meter. I'm sure a cheap (like $80) one from your local music store would be fine. Just don't get a $20 one. And we have yet to find a phone app that is accurate without needing to be calibrated, so don't use a phone app. If you can find a link to one you're considering, please post it here so that we can check if it's decent or not. You'll want to set your SPL meter to SLOW and C WEIGHTING.


I'm going to search one and I will post the link here. Thanks again!!


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PostPosted: Tue Mar 26, 2019 7:22 pm 
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Here a few options --> which one is best price/quality?

https://www.thomann.de/gb/digital_sound ... ImVuIn0%3D

https://www.keymusic.com/item/monacor-s ... vel-meter/

The second one is available at the local music store.

Also there is a second hand option --> the ST8850 --> https://www.marktplaats.nl/a/doe-het-ze ... ousPage=lr


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PostPosted: Wed Mar 27, 2019 7:45 am 
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The first or third option would work fine. The middle one only has A weighting so do NOT buy that one!

Greg

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PostPosted: Wed Mar 27, 2019 6:09 pm 
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Thanks Greg!! You're very helpful. I will try to buy the second hand one, and otherwise I will purchase the first one.

I will post the results here (could take a while)


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PostPosted: Tue Apr 02, 2019 2:58 am 
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I've received the decibel meter in fine shape and it seems to work:)

What the plan is: set up drums + bass + guitar in a room with similar same dimensions as the future studio (only the testroom will be a bit higher). And put the decibel meter on a few different spots --> in between + near the walls. The highest dB output will be the maintained number.

Any tips or remarks?


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PostPosted: Tue Apr 02, 2019 3:15 am 
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I've found that a good spot to measure with your meter, is more or less where the drummer's head is... of course, he might object if you remove his head, so try placing the meter a bit higher and a bit forward. If you have drums, bass and electric guitar all going at once, then another good spot is in the middle of an imaginary triangle that joins them.

Of course, in a small room, there won't be a lot of difference between measuring that at any point in the room: it's going to be pretty loud everywhere. Just make sure that you have the meter at least three feet away from anything that is loud, and greater distance for bigger things.

Also, do make sure your meter is set to "C" weighting and "Slow" response.

- Stuart -

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PostPosted: Tue Apr 02, 2019 3:36 am 
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Soundman2020 wrote:
I've found that a good spot to measure with your meter, is more or less where the drummer's head is... of course, he might object if you remove his head, so try placing the meter a bit higher and a bit forward. If you have drums, bass and electric guitar all going at once, then another good spot is in the middle of an imaginary triangle that joins them.

Of course, in a small room, there won't be a lot of difference between measuring that at any point in the room: it's going to be pretty loud everywhere. Just make sure that you have the meter at least three feet away from anything that is loud, and greater distance for bigger things.

Also, do make sure your meter is set to "C" weighting and "Slow" response.

- Stuart -


Thanks Stuart!!

The drummers head is also exceptionally big, so I'm not sure if I can carry something like that... We will put the meter in the middle of an imaginary triangle. And the meter to "C" + "Slow"

And the range on High I guess? 65-130dB?


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PostPosted: Fri Apr 05, 2019 7:13 pm 
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We did a few measurements yesterday. We maxed out around 115 dB.

But there are a few things unclear to me...

I guess the use of the SPL meter is only useful, when you use it together with a frequency meter? If you wan't a meaningful outcome, you need to know how much dB is produced at which frequencies, right? If you know this, then you can use the MSM Calculator to find out how much noise/sound is left.

Another uncertainty: you can't just subtract the STC (from the calculator/the amount of dB your isolation creates) from the sound you produces, right? For example: if you produce 100 dB at 80 Hz and your walls etc. have a STC from 60 dB at Hz, there is 40 dB left? Seems illogical to me, because with every 10 dB, the noise doubles (to our human ears)...

Last thing: the inverse square law. The first point where people can here me, is 5 meter away. So I wan't to calculate the loss of sound. I tried this a few times, but here is the thing: I can't figure out a way to really calculate from the source. This formula assumes that you're already at a certain distance from the source. And I imagine that in the first mm's you loose quite a lot, this is also what the formula indicates. How do I calculate this? What the loss of sound will be from the source?


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PostPosted: Sat Apr 06, 2019 2:01 am 
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Quote:
We did a few measurements yesterday. We maxed out around 115 dB.
That's not unusual. Very typical, in fact.

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I guess the use of the SPL meter is only useful, when you use it together with a frequency meter? If you wan't a meaningful outcome, you need to know how much dB is produced at which frequencies, right?
Sort of but not really... You measured using the "C" weighting curve, which already takes into account the way human ears work in relation to sensitivity of loud sounds. ("A" weighting is for quiet sounds). So that single number of 115 dBC already represents the sum total of all frequencies, where each one is weighted according to the way your ear perceives it. As you can see from the graph above, the weighting takes into account those frequencies. So if the levels around 300 Hz were very loud, that would cause the meter to read higher than if the levels around 30 Hz were very high, because your ear is a little less sensitive to 30 Hz than it is to 300 Hz. So from that point of view, the single number you measured is already indicative, to a certain extent, of the frequency content. If you measure the SAME sound on both A and C, then the difference between those two readings will tell you a lot about the spectral content: If the numbers are about the same, then most of the energy is in the mids and highs, but if there's a really large difference, then most of the energy is in the lows. For example, if you switch from C to A and the level drops 30 dB, then likely most of the energy is around the 50 Hz to 100 Hz bands, so it is very much "bass heavy".

Yes it would be better to use a meter such as the Phonic PAA 3 which also displays the level of each individual 1/3 octave band in addition to the overall level, but when you do that you'll see that there really isn't much addition to learn that you didn't already know from just looking at the meter and listening with your ears: Whichever sound you are hearing loudest, is probably responsible for most of the number you are seeing. If the snare sounds really loud compared to the rest of the band, then you know that most of the energy is in the low mids. If the bass sounds really loud, then most of the energy is in the lows.

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If you know this, then you can use the MSM Calculator to find out how much noise/sound is left.
Isolation calculators that give you a single number for estimated isolation are also weighted to show the total isolation, not the isolation at any give frequency. If the calculatos also gives you a detail graph, showing the estimated isolation in each 1/3 octave band, then that's more usueful, since you can compare it to the spectrum of the typical music you play, and to the Fletcher-Munosn (or other) equal loudness curves, to get an idea of how that sound will be perceived on the other side of the barrier. It's important to understand that the way humans perceive sound is not the same as the way a mic picks up sound.

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Another uncertainty: you can't just subtract the STC (from the calculator/the amount of dB your isolation creates) from the sound you produces, right?
Actually, you can! That's what the entire exercise is about. You can simply subtract numbers, as long as you are crtain that you are using the SAME scale for the numbers, and you understand what you are doing. If you are producing 115 dBC inside, and your wall isolates 55 dB, then you will get roughly 60 dBC outside. Note that the measured levels must be the same weighting, but that the isolation does not mention weighting at all... because isolation is not a measure of sound levels! It's a measure of the mathematical difference between two OTHER numbers that are some type of weighting scale. It might seem like a subtle difference, but it is extremely important to get this. There is no such things as "50 dBC isolation", because isolation is not a measure of Sound Pressure Level! dBA, dBC, dBX and all the other weighting scales. Isolation is just the mathematical difference between two numbers: by itself, it does not measure any physical property of sound. It just compares two numbers, and those two numbers MUST be on the same scale. So you can't say that if you measured 100 dBC inside and 60 dBA outside that means you have 40 dB of isolation. Not true, because you cannot compare dBC with dBA. They are on two different scales. That would be the same as saying that if you have ten kilograms of apples and take away 3 pound of apples, that you now have 7 kg left: not valid, because pounds and kilograms are two different weight scales.

This is very important to understand. You can only compare numbers that are on the same scale, and the DIFFERENCE between those numbers does not have any "scale" associated with it. It's just a difference.

So it is perfectly valid to say that if you have 90 dBC inside and 50 dBC outside, then the wall is providing 40 dB of isolation. But NOT that it is providing 40 dBC of isolation...

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For example: if you produce 100 dB at 80 Hz and your walls etc. have a STC from 60 dB at Hz, there is 40 dB left?
No. Because you are trying to compare kilograms of apples to bicycle wheels! :) STC is not a measure of anything at all: it's just an index number in a rating system, and is pretty much meaningless for talking about isolation in studios. STC is a single-number rating system that was devised several decades ago to give you an idea about how well an indoor wall, or door might isolate typical speech, or typical sounds in homes or offices. It does not consider full range music, and was never meant for that, so you cannot validly use it to say anything at all about isolation in studios, nor even isolation between outdoor sounds in cities, and indoors. It's fine if you want to know how well your bedroom wall isolates you from your kids screaming at each other in the room next door, but tells you nothing useful about how well your bedroom window isolates the sound of traffic on the freeway outside your window, or the sound of aircraft flying overhead, or the sound of the railway line a block away.

Forget STC.

What we are interested in for studio design, is "decibels Transmission Loss", often just abbreviated "TL". That's what we are talking about when we say a certain wall provides 45 dB of isolation. We really mean 45 dB of transmission loss. Which implies that a 100 dBC sound in one side will end up as 55 dBC on the other side, or also that a 100 dBA sound on one side will end up as 55 dBA on the other side. "TL" just tells you how much the numbers went down. And of course, the best idea is to look at the actual TL curve, because it is never a flat line: you always get more reduction in the highs than the lows, and there are usually some fairly serious dips and peaks that you might need to take into account.

That sort of gets back to the point you were trying to make, but not really... :) (Sorry to be so cryptic, but this is a more complex question than it seems at face value!)

So, if you really want to take things to extremes, you could indeed measure the SPL for each frequency band for every instrument that you plan to record, then look at the TL curve for the type of wall you plan to build, subtract the numbers for each individual frequency band, and that would show you what the sound levels for each frequency would look like on the other side of your wall. You could then compare that to the Fletcher-Muson curves, choose an arbitrary phon level that you like, and see if your calculated levels happen exceed that phon curve at any given point. That would be the real indication of how loud you would HEAR that sound on the other side of the wall. However, you would have to do that without using any weighting curves on your meter, because the weighing curves are actually derived from the equal loudness curves, so you'd be taking them into account twice if you used "A" or "C" weighting on your meter. You'd need a meter that can do "flat" or "unweighted" readings...

Or you could just measure using "C", subtract the isolation number, and be done with it! :)

Quote:
Seems illogical to me, because with every 10 dB, the noise doubles (to our human ears)...
When comparing levels on the same scale, and across the entire spectrum, yes. But not for individual tones. You can say that you listened to the song inside, then outside, and thought it was half as loud, so the isolation must be about 10 dB. True. But you can't do that for individual tones, such as listening to the bass play a low E inside, go outside estimate half as loud, and say that means the wall isolates 10 dB at 41.2 Hz. Not true, because your hearing isn't linear. Take a look at the equal loudness curves, and you will see that they are very close together at 40 Hz, but much further apart at 4 kHz, so an estimate of "half as loud" would be very different in actual dB levels for those two tones.

As with most rules of thumb, they work when you use them in the right way, but they don't hold true for all situations. The "10 dB is twice / half as loud" is only true for typical broad-spectrum sounds, not individual notes or narrow frequency bands.


Quote:
Last thing: the inverse square law. The first point where people can here me, is 5 meter away. So I wan't to calculate the loss of sound. I tried this a few times, but here is the thing: I can't figure out a way to really calculate from the source. This formula assumes that you're already at a certain distance from the source. And I imagine that in the first mm's you loose quite a lot, this is also what the formula indicates. How do I calculate this? What the loss of sound will be from the source?
The "standard" measuring distance for sound levels is 1 meter, or three feet (roughly). But that refers to sound sources that are small with respect to that distance, or similar in size. So you can measure a guitar, speaker, or vocals at 3 feet, but you would not want to measure a a concert grand piano at 3 feet, nor a cruise ship's diesel engine at 3 feet, because the piano is large in relation to 3 feet, and the ship's engine is huge in relation to that 3 feet. You would be measuring only a small part of the total sound put out by that engine: perhaps just the sound of one valve, not the entire engine. There are methods for figuring that out with respect to very large sound sources, but for the outside wall of single story house, it would be reasonable to measure at a distance of maybe 6 to 9 feet or so. Even at 3 feet, you won't be too far wrong.

I hope I haven't confused you too much! decibels and sound levels are a complicated thing... and that's without even going into the technicalities of sound power vs. sound pressure vs. sound intensity.... nor going into why it is fine to just SUBTRACT the numbers even though dB is a logarithmic scale, and subtracting logs is the same as dividing the base numbers, so how can it be valid to divide the numbers when you just want to know how much the subjective level went down... :) (it is valid: don't worry about it) That would just complicate things too much.

And you thought you were asking a simple question! :) Simple answer? "It's complicated"....

- Stuart -

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PostPosted: Sat Apr 06, 2019 8:53 pm 
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If you measure the SAME sound on both A and C, then the difference between those two readings will tell you a lot about the spectral content: If the numbers are about the same, then most of the energy is in the mids and highs, but if there's a really large difference, then most of the energy is in the lows. For example, if you switch from C to A and the level drops 30 dB, then likely most of the energy is around the 50 Hz to 100 Hz bands, so it is very much "bass heavy".


Interesting! We will try this the next time.

Quote:
If the calculatos also gives you a detail graph...


It does! I use the one posted on this forum:

https://docs.google.com/spreadsheets/d/ ... 1543869474

Quote:
What we are interested in for studio design, is "decibels Transmission Loss", often just abbreviated "TL"... ...Or you could just measure using "C", subtract the isolation number, and be done with it! :)


All right, so no frequency meters etc., just C weighting and also a A weighting to see if the frequency range is bass heavy or not. I think it is, with drums and bass.

And STC --> I will forget this. TL it is.

You're talking about 'the isolation number' and '45 dB Transmission Loss' --> you mean the loss at a certain frequency? Or in general? And if the latter is the case, how do I know what this number is? When I use a calculator like the one above


Quote:
You can say that you listened to the song inside, then outside, and thought it was half as loud, so the isolation must be about 10 dB. True. But you can't do that for individual tones, such as listening to the bass play a low E inside, go outside estimate half as loud, and say that means the wall isolates 10 dB at 41.2 Hz. Not true, because your hearing isn't linear.


Didn't know that!!

Quote:
The "standard" measuring distance for sound levels is 1 meter, or three feet (roughly)... ...but for the outside wall of single story house, it would be reasonable to measure at a distance of maybe 6 to 9 feet or so. Even at 3 feet, you won't be too far wrong.


I guess I understand what you mean, but I'm not completely sure. So let's say the source (a band jamming) is producing 115 dBC. The isolation of the structure has a Transmission Loss of 50 dB. There is 65 dBC left. Then I use the inverse square law (http://hyperphysics.phy-astr.gsu.edu/hb ... prob2.html) --> fill in 3 feet at 'd1', fill in 5m at 'd2' and 65 in I2 --> outcome is 50 dB --> so when you're 5m away, you hear 50 dBC? Or am I completely wrong now and am I confusing dB with dBC and dBA?


Quote:
And you thought you were asking a simple question! :) Simple answer? "It's complicated"....


Complicated it is... man!!! But you guys are amazing. The time and effort you take to help rookies like me...There is hope in this world!

It will take some time to completely get a grasp of everything, but with baby steps I'm getting closer! I'm not in a hurry and I want to know what I'm doing


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PostPosted: Wed May 01, 2019 3:50 am 
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I guess I understand what you mean, but I'm not completely sure. So let's say the source (a band jamming) is producing 115 dBC. The isolation of the structure has a Transmission Loss of 50 dB. There is 65 dBC left. Then I use the inverse square law (http://hyperphysics.phy-astr.gsu.edu/hb ... prob2.html) --> fill in 3 feet at 'd1', fill in 5m at 'd2' and 65 in I2 --> outcome is 50 dB --> so when you're 5m away, you hear 50 dBC? Or am I completely wrong now and am I confusing dB with dBC and dBA?


Yes, I think this is right. Because everything a human ear perceives is noted in dBC.

Quote:
You're talking about 'the isolation number' and '45 dB Transmission Loss' --> you mean the loss at a certain frequency? Or in general? And if the latter is the case, how do I know what this number is? When I use a calculator like the one above


This is the peak of the graph in a C weighting graph, I guess, but I'm not 100% sure...


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