STC Rating??
- Thread starter Tukkis
- Start date
Tukkis
New member
I'm just trying to understand how much sound according to the rating it will block out.
Also what is usually a good STC rating for a home studio?
I need something that will block out amps and drums. Not all together but something that doesn't annoy the rest of the household.
Tukkis
Also what is usually a good STC rating for a home studio?
I need something that will block out amps and drums. Not all together but something that doesn't annoy the rest of the household.
Tukkis
If you want to see this in action, go to www.auralex.com and click on auralex university. They have demonstartions of how noise is reduced by the use of various products, from sheetrock to their sheetblok product. It's pretty cool and the best way to understand the practical impact of building staggered stud walls, etc.
knightfly
GrouchyOldFartOnBatteries
STC is a GENERAL rating of sound isolation - it means different things at different frequencies. It was originally intended to block voice-range frequencies in residential areas, so is centered around 500 hZ - I have yet to see an actual formula for calculating STC. However, normally if the TL (Transmission Loss) of a wall is 52 dB @ 500 hZ, then the STC of that wall will (usually)also be 52 dB.
The difference is that STC is a "one size fits all" number designed to show the isolation for voice frequency ranges, where TL is measured and defined at several different frequencies. TL, in order to be valid, MUST state the frequency it refers to.
For today's music isolation, STC isn't the best measurement - When it was developed, there were no SUBWOOFERS, and hip-hop hadn't been born yet. There have been attempts at getting a NEW standard of wall ratings approved, but little support for the usual (dollar driven, mostly) reasons - this is called MTC, and stands for either Music Transmission Class or Machinery Transmission Class. Both take into account the lower frequencies involved in the classification.
Just because a wall is rated at 55 dB STC, does NOT mean it will reduce sound by 55 dB - this varies with the frequency, and is MUCH lower at low frequencies - That would make things seem like you couldn't stop drum noise very well, but the human hearing response (sorta) steps in and "saves the day" - humans don't hear as well at lower frequencies, nor at lower volume levels at those low frequencies - so a lesser reduction in sound at lower frequencies isn't as bad as you would think.
There are 'way more factors involved in isolation construction (I don't like the term "sound proofing", it infers you can TOTALLY block sound and I doubt ANY of us here could afford to do that) - For drum isolation, the lower frequencies pose a problem of more vibration getting into the building's framing, which can then vibrate walls in other rooms and result in what's called "flanking noise" - the term means the same as in war, where you try to "flank" the enemy (get around his defenses) - This is where the "room in a room" concept comes in. If you can keep the sound from ever GETTING to the framing/foundation of the building, then it CAN'T vibrate wall panels in other rooms. Problem solved.
Sorry for the length, that was probably 'way more than anyone asked for, and 'way less than there is... Steve
The difference is that STC is a "one size fits all" number designed to show the isolation for voice frequency ranges, where TL is measured and defined at several different frequencies. TL, in order to be valid, MUST state the frequency it refers to.
For today's music isolation, STC isn't the best measurement - When it was developed, there were no SUBWOOFERS, and hip-hop hadn't been born yet. There have been attempts at getting a NEW standard of wall ratings approved, but little support for the usual (dollar driven, mostly) reasons - this is called MTC, and stands for either Music Transmission Class or Machinery Transmission Class. Both take into account the lower frequencies involved in the classification.
Just because a wall is rated at 55 dB STC, does NOT mean it will reduce sound by 55 dB - this varies with the frequency, and is MUCH lower at low frequencies - That would make things seem like you couldn't stop drum noise very well, but the human hearing response (sorta) steps in and "saves the day" - humans don't hear as well at lower frequencies, nor at lower volume levels at those low frequencies - so a lesser reduction in sound at lower frequencies isn't as bad as you would think.
There are 'way more factors involved in isolation construction (I don't like the term "sound proofing", it infers you can TOTALLY block sound and I doubt ANY of us here could afford to do that) - For drum isolation, the lower frequencies pose a problem of more vibration getting into the building's framing, which can then vibrate walls in other rooms and result in what's called "flanking noise" - the term means the same as in war, where you try to "flank" the enemy (get around his defenses) - This is where the "room in a room" concept comes in. If you can keep the sound from ever GETTING to the framing/foundation of the building, then it CAN'T vibrate wall panels in other rooms. Problem solved.
Sorry for the length, that was probably 'way more than anyone asked for, and 'way less than there is... Steve
knightfly
GrouchyOldFartOnBatteries
"Should I drywall both sides of the interior room walls or leave the inner face open? Various drawings have shown it both ways" -
One thing that becomes more clear when studying acoustics for long periods, is that nothing is that clear. In order to answer that question, I'd need quite a bit more info on your specific situation. Things like what kind of structure is the "room in room" going to be inside of, what the function of the "RIR" will be, what size the room will be, (all THREE dimensions) , and probably several other facts of construction type, existing floor construction (strength is required to float a new room over existing floors, because it changes all loading points, etc.)
If you need more specific answers, I would join John Sayers' site (if you haven't already) and post your questions in their own thread so it's easier to keep things in perspective. Things get lost too easily when they're part of a different thread, plus it confuses things for the person whose thread gets "hijacked"... Steve
One thing that becomes more clear when studying acoustics for long periods, is that nothing is that clear. In order to answer that question, I'd need quite a bit more info on your specific situation. Things like what kind of structure is the "room in room" going to be inside of, what the function of the "RIR" will be, what size the room will be, (all THREE dimensions) , and probably several other facts of construction type, existing floor construction (strength is required to float a new room over existing floors, because it changes all loading points, etc.)
If you need more specific answers, I would join John Sayers' site (if you haven't already) and post your questions in their own thread so it's easier to keep things in perspective. Things get lost too easily when they're part of a different thread, plus it confuses things for the person whose thread gets "hijacked"... Steve
Last edited:
Rod Gervais
New member
Tukkis,
Steve hit this one right on the head.
STC relates basically to the intent of stoping the frequency range of the human voice - and thus doesn't work real well for studio design - although it (coupled with some other means of measurement) can lead you in the right direction.
What they actually do is to create a wall assembly - seal all the joints with acoustical caulk - and then transmit sound waves on one side of the wall - while measuring the remaining waves on the opposite side.
The measurements are taken from 50 to 6300 hz - with the intent to ensure that the greatest reductions are in that area of the human voice range - and then these indivudual TL values are averaged to create the stc rating (this is a weighted average).
So in order for this to be meaningfull to you - you really need to know the individual TL ratings used in the study rather than the weighted average itself.
Then you can calculate the actual isolation value of the wall for each of the frequencies in question.
This can vary by quite a bit - here is an example for you -
This is the data from a wall rated at STC 58 -
it's a double wall assembly - 2x4 wood studs - 16"oc - 1" air space between studs - 3" glass fiber insulation in each wall and one layer of 1/2" type X drywall on each face.
Now you might get excited at the thought of a 58db reduction in sound with just a single layer of 1/2" drywall - that is at least before you see the actual TL numbers.
Take a look:
Frequency...........TL
50hz..............14.9
63hz..............19.7
80hz..............24.7
100hz..............29.7
125hz..............33.7
160hz..............38.5
200hz..............43.1
250hz..............50.4
315hz..............55.6
400hz..............61.1
500hz..............63.7
630hz..............68.4
800hz..............73.3
1000hz..............77.2
1250hz..............80.5
1600hz..............85.4
2000hz..............84.9
2500hz..............74.4
3150hz..............74.1
4000hz..............79.1
5000hz..............84.4
6300hz..............87.6
As you can see - in those frequencies below 200hz - this wall is really not doing much at all - although it does much better than the STC rating would suggest for frequencies above 630hz.
In order to handle those lower frequencies you need mass - mass - and then more mass..........
I hope this helped.
Rod
Steve hit this one right on the head.
STC relates basically to the intent of stoping the frequency range of the human voice - and thus doesn't work real well for studio design - although it (coupled with some other means of measurement) can lead you in the right direction.
What they actually do is to create a wall assembly - seal all the joints with acoustical caulk - and then transmit sound waves on one side of the wall - while measuring the remaining waves on the opposite side.
The measurements are taken from 50 to 6300 hz - with the intent to ensure that the greatest reductions are in that area of the human voice range - and then these indivudual TL values are averaged to create the stc rating (this is a weighted average).
So in order for this to be meaningfull to you - you really need to know the individual TL ratings used in the study rather than the weighted average itself.
Then you can calculate the actual isolation value of the wall for each of the frequencies in question.
This can vary by quite a bit - here is an example for you -
This is the data from a wall rated at STC 58 -
it's a double wall assembly - 2x4 wood studs - 16"oc - 1" air space between studs - 3" glass fiber insulation in each wall and one layer of 1/2" type X drywall on each face.
Now you might get excited at the thought of a 58db reduction in sound with just a single layer of 1/2" drywall - that is at least before you see the actual TL numbers.
Take a look:
Frequency...........TL
50hz..............14.9
63hz..............19.7
80hz..............24.7
100hz..............29.7
125hz..............33.7
160hz..............38.5
200hz..............43.1
250hz..............50.4
315hz..............55.6
400hz..............61.1
500hz..............63.7
630hz..............68.4
800hz..............73.3
1000hz..............77.2
1250hz..............80.5
1600hz..............85.4
2000hz..............84.9
2500hz..............74.4
3150hz..............74.1
4000hz..............79.1
5000hz..............84.4
6300hz..............87.6
As you can see - in those frequencies below 200hz - this wall is really not doing much at all - although it does much better than the STC rating would suggest for frequencies above 630hz.
In order to handle those lower frequencies you need mass - mass - and then more mass..........
I hope this helped.
Rod