Drum Kit Noise Transmission

QuaranTD

Member
I'll start by saying that the department I am least qualified in and try not to waste anyones time in is sound. I've done my best to educate myself so I can hopefully ask the right questions as this particular problem falls in my lap currently. I am almost certain that the solution to our dilemma does not exist without hiring and paying for the appropriate engineers and designers and I am banging my head against a wall, but here it goes...

We are an old space bordered by neighboring lofts on three sides. Sound separation has always been an issue and addressed with varying degrees of success and effort at many times throughout our history. At this point our issues are generally minimal with amplified sound however we recently had a show in residence that utilized a drum kit. Our neighbor that lives in the loft adjacent to the back wall of the stage about 2 stories up has complained numerous times and this show is coming back for a longer run. I never doubted the validity of their complaints and set max levels and rescheduled rehearsal hours and lengths to accommodate their concerns. Rehearsals are rarely a huge problem but 8pm shows where energy is high seems to do the trick. I was never able to experience it from their side as they were always quite hostile. I was then told this had been done by an acoustician in the past and I recently found the report from well before my time.

The wall in question is, as far as we know, a 2 wythes brick party wall with insulating concrete and MLV + quilted fiberglass 1/4" tolerance sound blankets on our side, and furred out gypsum on our neighbors side. A sound sample at 100dBA in the space registered approximately 15dBA above the low ambient noise conditions in their room (*they also have no window and so are not exposed to outdoor ambient noise, but that's another issue), and was worse between 125Hz and 250Hz. Making a drum kit literally the worst thing we could put in the space.

Unfortunately building out a decoupled back wall with 2 layers of gypsum and mlv is out of the question for a host of reasons, some valid, and others not : /

Is there any way to effectively add mass without permanently losing space? Since the problem is in a lower range is there a semi-permanent solution that could be installed anytime a kit is brought in? We are already putting EPDM rubber under the kit platform to slightly dampen any vibration transferred through the floor.

I am ready to be disappointed but their concerns are real. Any helpful solution that I can put in place would be appreciated and contribute a more peaceful month for both myself and our neighbor.
 

TimMc

Well-Known Member
Premium Member
Sue him for harrassment, so he has to prove that the previous abatement is ineffective.
 

jtweigandt

Well-Known Member
Your drummer might not like it, but an electronic drum set would let you direct the sound forward and eliminate the live sound going directly to the back wall and transmitting through the building.
Might ultimately prove cheaper and more effective than attempting further abatement.
Or a "band shell" arrangement drum cage with the plexi on the back taking the "first hit" so your actual wall only experiences attenuated not direct percussion sound.

Of course the other question that comes to mind.. which was there first.. a performance space or the Tenant? Not to make light or at least try to accommodate... but in the end.. Dude.. you moved right off the runway.. planes take off there.
 

QuaranTD

Member
I was thinking an electronic kit would be a great solution so we could route it to the appropriate monitors and not lose the experience for the audience. Going to continue trying to sell that one...

Same with the cage, which we DO have.

As for who was here first....I personally don't know, but we're talking Jurassic period for both tenant and space. It's been a thing for at least 40 years but drum kits weren't ever utilized in our space till recent.
 

TimMc

Well-Known Member
Premium Member
I was thinking an electronic kit would be a great solution so we could route it to the appropriate monitors and not lose the experience for the audience. Going to continue trying to sell that one...

Same with the cage, which we DO have.

As for who was here first....I personally don't know, but we're talking Jurassic period for both tenant and space. It's been a thing for at least 40 years but drum kits weren't ever utilized in our space till recent.
The bigger question I have - with 2 courses of brick I have a difficult time imaging an acoustic drum kit penetrating that much mass. I think that are other factors involved but we'll have to suss those out. Using an electronic kit will not help because it will be amplified. IF acoustic drums are leaking around, so will the loudspeaker output.
 

FMEng

Well-Known Member
Fight Leukemia
It sure can't hurt to rent a set of electronic drums, and give it a try. A full drum enclosure, with a lid, would also be worth a try, but I doubt a partial shell would help enough. Mic the kit inside the enclosure. The upside to either of those solutions is that the over all loudness and amount of bass energy is now controllable at the sound console. The drummer will likely prefer the enclosure over electronic drums, but the latter is most effective. Churches often deal with this because the drums overwhelm everything else, preventing a good mix at modest house sound levels.

It's not just the drums. The other musicians on stage are playing loudly to hear themselves over the drums. The loudness of the whole group can be substantially lowered by attenuating the drums. Stage monitors are another factor that lead to ever increasing stage levels. (I need more me!) Time for in-ear monitors for the musicians. Get rid of guitar amps. Use one of the great amp emulators for electric guitar, and a direct box for the bass guitar, with some tube saturation/compression at the console.

It's not clear from your writing whether a fix was attempted, or never made it beyond an engineer's recommendation. The other question is whether the scope of work considered live music or just considered theater. Low frequency energy will go through brick. Low frequency sound is the most difficult to attenuate, so there are no easy and cheap fixes. The solution has to be extensive and complete in order to be effective. A fix would need to be properly carried out in order to work as predicted.

The little speech I've given to construction superintendents, before we start building radio studios, is that every detail in the wall, window, and door design counts. A missing piece of rubber, a gap in caulking, a temporary brace left in, an unsealed penetration, or a dozen other things like that, can substantially limit the performance of the acoustic isolation. The isolation is predictable and measurable, and guess who we come after if it isn't good? Fear of failure and attention to detail are vital things when it comes to construction for acoustics.

Another possibility would be to move the occupant out and rent the affected loft to keep it unoccupied. Maybe it could be sublet to a staff member or a night worker.
 

MNicolai

Well-Known Member
Premium Member
Fight Leukemia
There's really no way to guesstimate a best path forward over the internet. There's a decent chance it's not simply what's going through the wall, but also what noise is being carried through structure-borne vibrations, holes/gaps/penetrations, etc. You could certainly throw furring, batting, and a couple layers of gyp board up only to find that has little or no improvement because the sound is leaking somewhere or the overall assembly isn't effective at mitigating low-frequencies.

Potentially if you share the report there will be some information that can be gleaned from it, but it really depends if the acoustician tested both sides of the wall or just the tenant's side, and to what extent they documented the conditions.

It's also hard to know if the problem is loudness, perceptible vibration, and/or if the sound is decently quiet but the tenant has a quiet unit and being able to hear the sound at all is the problem.

I dropped the assembly you described -- at least the best that I could imagine it -- into our Insul software. I ignored the blankets because unless they have absolutely 100% coverage of that wall, they are likely doing nothing at all in terms of sound transmission reduction. Below are the results that came back.

First image is wood studs on 24" centers for the furring with the assumption there's batting in those stud cavities. Second image is 16" spacing. Note that there's a sizable difference around 125/250 depending on the stud spacing. The gyp. board basically acts like a drum head and resonates between the studs so the stud spacing directly impacts the resonant frequencies. Also note that these results are assuming laboratory conditions. If the tenant has light switches, power receptacles, and such cut into that drywall, those are going to be sizable leaks. The appropriate way to remedy that would be to use acoustic putty behind the electrical backboxes to fully seal the penetrations, but it's very unlikely that would've been done here so we should assume the gyp. board has holes cut into it.

1655878388023.png



1655878419733.png


You also don't know how the gyp. board was finished. Was it installed with one layer or two? Was it sealed with caulk where it meets the floor before the baseboard was installed and similarly at the top before crown moulding was installed? If not, more leaks.

Cracks in the grout of the bricks? More leaks.

Think of it like driving down the freeway and you have your window open just a hair. Even the tiniest of air gaps can allow a ton of noise through.

Drum kit is sitting directly on a hard floor without carpet or other underlayment? You're gonna have more structure-borne vibration from the kit that will "tuning fork" it's way through the floor and wall.

Especially at low-frequencies, you're not just looking to throw mass at it to isolate the airborne noise. You need to mechanically decouple at least one side of the partition so the surface layer isn't rigidly attached to the rest of the assembly otherwise both the airborne and structure-borne vibration will mechanically vibrate directly through the assembly all the way to the tenant's gyp board.

Now...if you build out an insulated gyp. board addition to your side of the wall, you may see a 10dB improvement...but, notice something. If we're comparing with the results above -- there is only a tangible improvement at 250Hz if the tenant's side has 16" O.C. studs. If they have 24", 125Hz improves but there is almost no difference at all around 250. Also -- the more isolation you attempt, the more important it is to seal every crack, hole, and penetration -- or you will end up spending a lot of money to get no where.

1655879925061.png


All of this is to say that you if you really want to resolve this without asking the drummer to play softer, you will need a professional on-site acoustical study and likely the permission of the tenant to enter their space. Throwing more blankets on the wall will not do anything.

As for an electronic drum kit -- if you're amplifying it to the same level as normal, the airborne noise may or may not improve. Low-frequencies tend to be omnidirectional so even if the speakers are pointed away from the wall, the wall will still get a lot of 125/250. However -- if that drummer had previously been backed right up to that wall, the wall may see just a little bit less SPL than before. An electronic kit may also reduce some of the structure-borne vibration of the kit "tuning forking" its way through the floor and into the demising wall. If you continue to use an acoustic kit, definitely put a thick rug underneath it if you don't have one there already.

Disclaimer: The graphics and calculations above are not acoustical advice. They are conceptual, rough order of magnitude approximations that surely do not accurately reflect existing conditions and do not account for other possible weak points for sound transmission. Engage an acoustician for an on-site study before making any decisions.
 

QuaranTD

Member
There's really no way to guesstimate a best path forward over the internet. There's a decent chance it's not simply what's going through the wall, but also what noise is being carried through structure-borne vibrations, holes/gaps/penetrations, etc. You could certainly throw furring, batting, and a couple layers of gyp board up only to find that has little or no improvement because the sound is leaking somewhere or the overall assembly isn't effective at mitigating low-frequencies.

Potentially if you share the report there will be some information that can be gleaned from it, but it really depends if the acoustician tested both sides of the wall or just the tenant's side, and to what extent they documented the conditions.

It's also hard to know if the problem is loudness, perceptible vibration, and/or if the sound is decently quiet but the tenant has a quiet unit and being able to hear the sound at all is the problem.

I dropped the assembly you described -- at least the best that I could imagine it -- into our Insul software. I ignored the blankets because unless they have absolutely 100% coverage of that wall, they are likely doing nothing at all in terms of sound transmission reduction. Below are the results that came back.

First image is wood studs on 24" centers for the furring with the assumption there's batting in those stud cavities. Second image is 16" spacing. Note that there's a sizable difference around 125/250 depending on the stud spacing. The gyp. board basically acts like a drum head and resonates between the studs so the stud spacing directly impacts the resonant frequencies. Also note that these results are assuming laboratory conditions. If the tenant has light switches, power receptacles, and such cut into that drywall, those are going to be sizable leaks. The appropriate way to remedy that would be to use acoustic putty behind the electrical backboxes to fully seal the penetrations, but it's very unlikely that would've been done here so we should assume the gyp. board has holes cut into it.

View attachment 23175


View attachment 23176

You also don't know how the gyp. board was finished. Was it installed with one layer or two? Was it sealed with caulk where it meets the floor before the baseboard was installed and similarly at the top before crown moulding was installed? If not, more leaks.

Cracks in the grout of the bricks? More leaks.

Think of it like driving down the freeway and you have your window open just a hair. Even the tiniest of air gaps can allow a ton of noise through.

Drum kit is sitting directly on a hard floor without carpet or other underlayment? You're gonna have more structure-borne vibration from the kit that will "tuning fork" it's way through the floor and wall.

Especially at low-frequencies, you're not just looking to throw mass at it to isolate the airborne noise. You need to mechanically decouple at least one side of the partition so the surface layer isn't rigidly attached to the rest of the assembly otherwise both the airborne and structure-borne vibration will mechanically vibrate directly through the assembly all the way to the tenant's gyp board.

Now...if you build out an insulated gyp. board addition to your side of the wall, you may see a 10dB improvement...but, notice something. If we're comparing with the results above -- there is only a tangible improvement at 250Hz if the tenant's side has 16" O.C. studs. If they have 24", 125Hz improves but there is almost no difference at all around 250. Also -- the more isolation you attempt, the more important it is to seal every crack, hole, and penetration -- or you will end up spending a lot of money to get no where.

View attachment 23178

All of this is to say that you if you really want to resolve this without asking the drummer to play softer, you will need a professional on-site acoustical study and likely the permission of the tenant to enter their space. Throwing more blankets on the wall will not do anything.

As for an electronic drum kit -- if you're amplifying it to the same level as normal, the airborne noise may or may not improve. Low-frequencies tend to be omnidirectional so even if the speakers are pointed away from the wall, the wall will still get a lot of 125/250. However -- if that drummer had previously been backed right up to that wall, the wall may see just a little bit less SPL than before. An electronic kit may also reduce some of the structure-borne vibration of the kit "tuning forking" its way through the floor and into the demising wall. If you continue to use an acoustic kit, definitely put a thick rug underneath it if you don't have one there already.

Disclaimer: The graphics and calculations above are not acoustical advice. They are conceptual, rough order of magnitude approximations that surely do not accurately reflect existing conditions and do not account for other possible weak points for sound transmission. Engage an acoustician for an on-site study before making any decisions.

This is really helpful for my own understanding of the issues and the diagrams are much appreciated. Thank you!

There are a multitude of the problems you describe and some of them are addressed in the older report. The acoustician was under the impression that due to the frequency range they were experiencing transmitted noise at the sound was "likely to be traveling directly through the wall rather than passing through gaps or cracks". There are however many points where this could be contributing to the issue as the wall is incredibly old and I can see evidence of past installation into the masonry. Using the (NIC) system the test results apparently registered between NIC-63 and NIC-64.

The test was conducted with both a floor mounted speaker and with our house system in the grid. The height puts our main monitors approximately equal with the demising wall of the apartment. After this report was finished the mains were decoupled from the grid using resilient hangers and and wire rope as they noticed an approximate 5dBA difference between the systems. We rarely experience issues with amplified sound and the drum kit has truly been the culprit of every encounter I have had.

I always believed those blanket didn't do much as they do not cover the entirety of the wall and leave a 4' gap at ground level : /.

Especially at low-frequencies, you're not just looking to throw mass at it to isolate the airborne noise. You need to mechanically decouple at least one side of the partition so the surface layer isn't rigidly attached to the rest of the assembly otherwise both the airborne and structure-borne vibration will mechanically vibrate directly through the assembly all the way to the tenant's gyp board.

Now...if you build out an insulated gyp. board addition to your side of the wall, you may see a 10dB improvement...but, notice something. If we're comparing with the results above -- there is only a tangible improvement at 250Hz if the tenant's side has 16" O.C. studs. If they have 24", 125Hz improves but there is almost no difference at all around 250. Also -- the more isolation you attempt, the more important it is to seal every crack, hole, and penetration -- or you will end up spending a lot of money to get no where.

This was the opinion cited at the end of the report. They estimated a "possible" 10dBA improvement from the buildout described. It is INCREDIBLY helpful to see your results and how the effectiveness at 250Hz might be almost negligible depending on the stud layout of our neighbors portion of the demising wall.

All of this is to say that you if you really want to resolve this without asking the drummer to play softer, you will need a professional on-site acoustical study and likely the permission of the tenant to enter their space. Throwing more blankets on the wall will not do anything.

I 100% agree and feel currently resigned to non structural measures while putting together a strong argument for another survey and quote in the near future if programming continues this trajectory

As for an electronic drum kit -- if you're amplifying it to the same level as normal, the airborne noise may or may not improve. Low-frequencies tend to be omnidirectional so even if the speakers are pointed away from the wall, the wall will still get a lot of 125/250. However -- if that drummer had previously been backed right up to that wall, the wall may see just a little bit less SPL than before. An electronic kit may also reduce some of the structure-borne vibration of the kit "tuning forking" its way through the floor and into the demising wall. If you continue to use an acoustic kit, definitely put a thick rug underneath it if you don't have one there already.

The drummer is about 10' from the demising wall. I was hoping that switching to an electric kit would reduce the structure borne vibration as you said and allow us to even slightly drop the SPL.

It's also hard to know if the problem is loudness, perceptible vibration, and/or if the sound is decently quiet but the tenant has a quiet unit and being able to hear the sound at all is the problem.
This may be the root of it all as our neighbor happens to be an older author. I am trying to work with them as much as possible but currently they are uninterested in any options that involve work in their space.

Thanks again for taking the time to lay some of this out!
 

gafftaper

Senior Team
Senior Team
Fight Leukemia
Not my area of expertise, but perhaps a combination of e-drums and cardioid subwoofers to send the bass the other direction would be worth exploring? Hearing the QSC KS212C cardioid sub at NAMM a couple years ago was amazing. There really is 15 db difference in what you hear in front vs the rear. The same effect can be achieved with other speakers manually if you have the right gear and the right person to design the setup.
 

QuaranTD

Member
Getting into the loft space and carefully listening could reveal some very important details. Where is the sound coming from? Is there a leak? Is it coupled into the floor or
ceiling? Is it low enough that a little white noise would mask?

Addition of "Electro-Acoustic masking" in a different study from a capital project in the early 90's was proposed. They suggested digital noise generators and concealed loudspeakers in the lofts. As far as I can tell that suggestion never took root as the tenant, who I believe was the same at the time, dismissed it out of hand. I LOVE the idea.
 

QuaranTD

Member
Not my area of expertise, but perhaps a combination of e-drums and cardioid subwoofers to send the bass the other direction would be worth exploring? Hearing the QSC KS212C cardioid sub at NAMM a couple years ago was amazing. There really is 15 db difference in what you hear in front vs the rear. The same effect can be achieved with other speakers manually if you have the right gear and the right person to design the setup.
If we can make the switch to an electric kit this suggestions is a great idea for me to bring to our sound designer. Thanks!
 

TimMc

Well-Known Member
Premium Member
This is really helpful for my own understanding of the issues and the diagrams are much appreciated. Thank you!

There are a multitude of the problems you describe and some of them are addressed in the older report. The acoustician was under the impression that due to the frequency range they were experiencing transmitted noise at the sound was "likely to be traveling directly through the wall rather than passing through gaps or cracks". There are however many points where this could be contributing to the issue as the wall is incredibly old and I can see evidence of past installation into the masonry. Using the (NIC) system the test results apparently registered between NIC-63 and NIC-64.

The test was conducted with both a floor mounted speaker and with our house system in the grid. The height puts our main monitors approximately equal with the demising wall of the apartment. After this report was finished the mains were decoupled from the grid using resilient hangers and and wire rope as they noticed an approximate 5dBA difference between the systems. We rarely experience issues with amplified sound and the drum kit has truly been the culprit of every encounter I have had.

I always believed those blanket didn't do much as they do not cover the entirety of the wall and leave a 4' gap at ground level : /.



This was the opinion cited at the end of the report. They estimated a "possible" 10dBA improvement from the buildout described. It is INCREDIBLY helpful to see your results and how the effectiveness at 250Hz might be almost negligible depending on the stud layout of our neighbors portion of the demising wall.



I 100% agree and feel currently resigned to non structural measures while putting together a strong argument for another survey and quote in the near future if programming continues this trajectory



The drummer is about 10' from the demising wall. I was hoping that switching to an electric kit would reduce the structure borne vibration as you said and allow us to even slightly drop the SPL.


This may be the root of it all as our neighbor happens to be an older author. I am trying to work with them as much as possible but currently they are uninterested in any options that involve work in their space.

Thanks again for taking the time to lay some of this out!

So what, other than being a pain in your backside, is this person doing to the theater? Calling police? Calling board members?

This is my point: if he won't let the theater's acoustician/expert into his space to help with remediation, he's harassing the theater. I suspect he's more into controlling things than actually fixing the problem, but the theater cannot assess the problem without his cooperation, which I why I suggested lawyers.
 

QuaranTD

Member
They have not called police although I am not entirely worried about that response given my experience with local PD response times for non-violent situations. The show would be done by the time they arrived. They are part of a residential Co-op that houses all our neighbors and so we try very hard to maintain healthy relationships with them all.

Mostly everyone is content to just let me field irate correspondence, which is fine. In my digging into the problem I am not entirely convinced that the tenant doesn't have a legitimate concerns and the level in their unit is excessive given the lack of ambient noise. My goal in the end are solutions to not have to restrict artists in our space and not mediating this issue regularly.

If this next run proves horrendous you may very well be right but I would like to explore all alternatives first.
 

Jay Ashworth

Well-Known Member
1) Is the drum kit isolated sufficiently up of the floor?
2) Is the drum kit muffled? Drummers generally know how to accomplish this, but that doesn't mean that you can't.
3) Do you have a (calibrated) sound level meter that you can use to evaluate the changes you make?

And all of what Mike said. :)
 

QuaranTD

Member
1) Is the drum kit isolated sufficiently up of the floor?
2) Is the drum kit muffled? Drummers generally know how to accomplish this, but that doesn't mean that you can't.
3) Do you have a (calibrated) sound level meter that you can use to evaluate the changes you make?

And all of what Mike said. :)
Originally it was just carpeting which we are replacing with a platform on top of 1" EPDM Rubber. The drum kit wasn't muffled initially and is a conversation we will have when they come back into rehearsal. I have a meter that I have been using to set max levels in our space and ultimately am trying to arrange a visit during the rehearsal period to meter the transmission with the drummer playing.
 

TimMc

Well-Known Member
Premium Member
And after some reflection, I see this as a 2 way street. The offended person will not cooperate and the theater is unwilling to institute rules or controls because they "limit artistic freedom".

I have a problem with both, to some degree. I like the idea of artistic freedom and I've watched many, many thousands of Dollars/Pounds/Euros frittered away in the pursuit thereof. I've watched great theater, music, and TV made with all kinds of restrictions and limitations on "freedom." File me under "conditionally curmudgeonly".

I do not think the problem is <100Hz, but I could be wrong. Drums have an incredibly high peak SPL that are also very, very brief (milliseconds; it can defy accurate measurement with mechanical movement meters). What we measure as being 98dBA a few feet from a drum could easily have a peak 30dB higher. As Mike N points out, getting enough NCF to render the offending 'noise' inaudible will be a huge exercise and likely a very expensive one as well, especially if the neighbor wishes only to complain rather than participate.

For the theater, is the drum kit amplified? Is the bass drum EQd with a big "LF haystack" that emphasizes the <100Hz spectrum; i.e. does it sound like a car stereo? Does the neighbor complain about other program audio or only the drum kit? If it's just the drums, I think the peak energy is the initial source of the complaint. If the complaint is about *music* in general and drums in particular, I'm not sure there is an immediate solution.

What's the theater's limit to make this person happy? How much money can be willingly spent before the venue/producer says "okay, we can't do *this* anymore"?
 

RonHebbard

Well-Known Member
Premium Member
And after some reflection, I see this as a 2 way street. The offended person will not cooperate and the theater is unwilling to institute rules or controls because they "limit artistic freedom".

I have a problem with both, to some degree. I like the idea of artistic freedom and I've watched many, many thousands of Dollars/Pounds/Euros frittered away in the pursuit thereof. I've watched great theater, music, and TV made with all kinds of restrictions and limitations on "freedom." File me under "conditionally curmudgeonly".

I do not think the problem is <100Hz, but I could be wrong. Drums have an incredibly high peak SPL that are also very, very brief (milliseconds; it can defy accurate measurement with mechanical movement meters). What we measure as being 98dBA a few feet from a drum could easily have a peak 30dB higher. As Mike N points out, getting enough NCF to render the offending 'noise' inaudible will be a huge exercise and likely a very expensive one as well, especially if the neighbor wishes only to complain rather than participate.

For the theater, is the drum kit amplified? Is the bass drum EQd with a big "LF haystack" that emphasizes the <100Hz spectrum; i.e. does it sound like a car stereo? Does the neighbor complain about other program audio or only the drum kit? If it's just the drums, I think the peak energy is the initial source of the complaint. If the complaint is about *music* in general and drums in particular, I'm not sure there is an immediate solution.

What's the theater's limit to make this person happy? How much money can be willingly spent before the venue/producer says "okay, we can't do *this* anymore"?
"conditionally curmudgeonly".
LOVE it.
Toodleoo!
Ron Hebbard
 

Users who are viewing this thread