LOW FREQUENCY IMPACT NOISE

[soguale]

Hello:
I have a home studio, it sounds decent, but I´m having low frequency impact noise comming from the streets.

It did not happen before becouse the streets were made of asphalt , now the treets was rebuilt whit concrete.
It ´s very hard and it transsmit the noise to my studio.

The noise floor in my recording room is 25 db, when a bus croos the streets Makes noise( boom toc toc ), and the noise is about 6 to 8 db louder.
In my control room the noise floor is about 33db and wne the bus croos the streets the noise is 6 to 8 db louder.
Should I float my floor and walls?
I´ve read a STC for a 12mlm Gypsum Board is 15 db for 125 hz.
That´s enough soundproofing for solve this problem?
The recording room is 7 meter long, 5 meter wide, 4,30 meter hi.
(sorry about my english i do speak spanish)
Thanks!

[lilith_envy]

Your sound issue is transmited sound through the earth, floor and walls.

Can you tell us more about the studio and its construction?
IS it in a bedroom or was the studio purspose built.

Walls?
Floor?

I believe there is a Spanish speaking section in this forum.

[xSpace]

Like Ms. lilith_envy said, some of the issue is with the direct earth connection. Other things that will increase sound is that generally speaking, when roads are re-worked they get wider, and wider means the sound will get closer to your area. A heavy connection like concrete, if it is bedded on a hard earth connection, can move directly into your structure via the rock or frozen ground.

"I´ve read a STC for a 12mlm Gypsum Board is 15 db for 125 hz.
That´s enough soundproofing for solve this problem?"


What you are trying to say, I assume is that the transmission loss value at a specific frequency is relevant to your case. The Sound transmission Class (STC) of a piece of sheetrock is not given in reference to that piece of material. And in the hunt for isolation, mass is the determining factor, so a 1/2 inch (12 mm) would give less results, a lower stc and a reduced transmission loss, than 5/8 inch (16 mm) of mass would.

The loss(transmission loss @ 125 Hz) is a product of the thin sheetrock, one sheet or multiple sheets, it's still there:) like a window that is open and the frequency can move in or out of it,


You are wanting to attack the 50 Hz and lower area, this is not an stc thing but a product of the density of the material and how well it can support a barrier from low frequency.

[soguale]

Like Ms. lilith_envy said, A heavy connection like concrete, if it is bedded on a hard earth connection, can move directly into your structure via the rock of frozen ground.

"

That``s exactly wath happens, here are a sample , normalized to 0 db.
So how can I solve or minimize this problem.?
Do youy need more information?
Thanks!!

[gullfo]

can you localize where the sound is coming in? the walls/ceiling? a window? vents? floor? if you have (get) a contact microphone (or mechanic stethoscope, although the mic will let you record and analyze the frequency content) and put it on the concrete floor - what are you getting? same for walls windows ducts, etc etc

[soguale]

can you localize where the sound is coming in? the walls/ceiling? a window? vents? floor? if you have (get) a contact microphone (or mechanic stethoscope, although the mic will let you record and analyze the frequency content) and put it on the concrete floor - what are you getting? same for walls windows ducts, etc etc

Yes ! it comes from ceiling the most, walls, and floor, i´ve tryed the contact microphone, and the same frome avery where.More or less db. the noise is there.

Here are the sample recorded. And a picture showing the frecuency analisys

Any solution,? please!!!!

thanks!!!

[gullfo]

It structural in it's transfer - depending on your options to build a decoupled room within the existing space, or not.

[soguale]

It structural in it's transfer - depending on your options to build a decoupled room within the existing space, or not.

Yes I know that.
I could built a decoupled Room.

I can not built a concrete floating floor , but I do can built a wooden floating floor.

The Q is how much, do I need to do for isulating those 6 to 8 low frecuency db.

[xSpace]

Can we get a picture of this room...I'm thinking a window or a door is making this issue.






if it comes from the ceiling area first, then it(sound) has to travel a longer path or comes from overhead, typically it will be the floor/wall assembly and any window aperture involved.

[gullfo]

to isolate the 60-80hz effectively you need to have a natural resonance down around 20-25hz (basically 1/3) (which should be possible using say 12mm 30 hardness neoprene rubber or Sorbathane under the isolation wall framing). then you need to decouple the floor and ceiling - preferable the ceiling uses the decoupled walls for support so it's separated from the structure, and the floor use a damped membrane approach. you'll also need mass to ensure the actual wall and ceiling assembly resonance is low enough so 2x 16mm drywall. the air gap between the isolation walls and exterior is lightly filled with 15-24kg/m3 insulation.

[xSpace]

Sounds Good Glenn...can we get the data on that to interpret how this actually works from a verified testing area?


I understand how it >might< perform, but I have no idea if it will or will not, and might actually be more work than needed with a deleterious effect in the end.

I think of placing a lot of weight on a basic structure...with no field testing on the neoprene as to the weight imposed, and I have to wonder, why even do it, what is my margin for error?

[gullfo]

Brien - actually a reasonably high resonance frequency like that would be decoupled easily as described. calculating - there are a number of online resources to use to calculate it (Mason Industries, Sorbathane etc who provide isolation products for just this purpose and tables for calculating this) but when you get down to a target of ~40hz and less though the decoupling becomes much more dependent on precision...

[Jabbaz]

Make sure there is no significant sub-60Hz frequency content. If they aren't properly configured, some spectrum analyzers may have difficulty showing low freq content for impulses.

Neoprene won't do much at lower frequencies due to the static deflection needed. If there is really low freq content then you're looking at needing a sprung floor with some serious static deflection.

[soguale]

Make sure there is no significant sub-60Hz frequency content. If they aren't properly configured, some spectrum analyzers may have difficulty showing low freq content for impulses.

Neoprene won't do much at lower frequencies due to the static deflection needed. If there is really low freq content then you're looking at needing a sprung floor with some serious static deflection.

I just put a C414 in the recording room, and began to record, I wanted to know what noise could to interfere in a typical xy strings recording session.
If a can to minimize that low noise, about 10 db I suppouse could be right.
Do im wrong?

[Jabbaz]

Make sure there is no significant sub-60Hz frequency content. If they aren't properly configured, some spectrum analyzers may have difficulty showing low freq content for impulses.

Neoprene won't do much at lower frequencies due to the static deflection needed. If there is really low freq content then you're looking at needing a sprung floor with some serious static deflection.

I just put a C414 in the recording room, and began to record, I wanted to know what noise could to interfere in a typical xy strings recording session.
If a can to minimize that low noise, about 10 db I suppouse could be right.
Do im wrong?

In order to figure out how to mitigate the noise, you need to figure out what range of frequencies are ACTUALLY contained in the vibration intrusion. If the duration of the impulse is less than the duration of a cycle of a given frequency (say 20Hz for example, duration of 50ms), then your analyzer software may not recognize that there is content at that frequency.

In other words, contrary to the spectrum you provided, there may be sub 60Hz frequency content. This may change the design that you will need to mitigate the intrusion.

I would hate for you to go to the expense of building a floating floor to target 60Hz+ vibration, only to discover that the problem extends well below this.

EDIT: I would get a proper evaluation done by a qualified acoustic engineer.