An ounce of prevention by contacting Acoustical Surfaces Inc. Sound will find the weakest link s. Many dry wallers will jack the gypsum board up tight to the ceiling with a foot jack in order to achieve a nice tight joint at the ceiling where it is visible.
This frequently will leave a void or a leak at the floor juncture, which will eventually be covered with a piece of thin baseboard and will be out of sight and out of mind. Failure to caulk the joint between the wall and the floor can reduce even a high performance 50 STC rated wall to STC, far below the minimum building code standard of 45 STC.
This will mean the difference between satisfactory sound isolation and being able to hear your neighbors more than you care to. Remember, if you can hear them they can hear you!
The higher the STC rating, the better the sound isolation characteristics of the assembly will be. Most building codes require a minimum design for floors and wall construction to have an STC rating of 50 but will accept a minimum of 45 by actual field-testing. The sound will move from one room to another through direct and indirect paths. Some amount of energy will travel through or around a wall or ceiling.
It is important to understand that while sound can travel through air pockets like ductwork, stud and ceiling joist cavities, it can also be conducted along studs, joists, pipes, concrete and glass.
Sound vibration uses a rigid surface to travel, like your voice on a string between two cans. The string is a conductor just like a stud or joist. A common myth is that if you don't treat every surface, all of your soundproofing efforts will have been in vain.
This is simply not the case at all. If you significantly reduce the sound passing through the one main wall, for example, that's great. What remains will likely be flanking noise to a fair degree. While every structure is different, treating the one main "direct" pathway will generally prove satisfactory for most people. This generally reduces the sound to a tolerable level, but will not eliminate it.
There are a few common pathways where sound vibration often travels. The trick is to get creative and understand what pathways your flanking sound may travel and determine if anything can be done to reduce it. General advice would be to assess possible flanking pathways before treating the single wall or ceiling.
If there are too many flanking paths, the project may be bigger than you bargained for, and an acoustical consultant should be brought in. As always, if the project proves more than you can wrap your arms around, consider calling in a professional consultant from the National Council of Acoustical Consultants www.
You can get an idea of potential flanking using an inexpensive drugstore stethoscope. When the noise is occurring, have a listen to the main wall or ceiling, then listen to adjacent walls, floor or ceiling. Keep in mind that flanking sound will be reduced when you treat the main ceiling or wall. This technique will give you an idea of what you are up against.
A common noise pathway is through the floor framing system under the wall. In some construction, there is a joist system that travels under the offending wall. The floor systems on either side of the wall are connected, so while there is no open-air path from his side to yours, the floor framing itself can conduct the vibration from his side to yours.
This may or may not be a significant flanking pathway. Another similar path is through the ceiling joist system. There are times when an attic area is common to both rooms. Vibrations from the offending room are transmitted through the attic air cavity or conducted through the joists themselves. You may need to consider the option of soundproofing your ceiling to achieve the soundproofing results required. The last of the major paths is through sidewalls.
The walls in your unit are usually directly connected to the walls in the unit next door. Take a look at soundproofing your existing walls for further information and suggestions. It is important that the glazing is not continuous across the wall line between spaces and that a break is provided. This is not ideal from an acoustic point of view and additional measures to be provided to reduce flanking sound transmission. This has to be looked at on a case by case basis in coordination with a professional acoustical consultant.
In addition to horizontal flanking sound transmission, vertical flanking sound transmission should also be controlled. But what does this 8 dB improvement mean in terms of subjective perception? The subjective response for variation of sound pressure level has been investigated for a group of people and the results are summarised in the table below. People are becoming more and more demanding for acoustic privacy in their homes especially when a person is purchasing a permanent home rather than renting an apartment.
To minimise annoying disturbances caused by noise transmission between dwelling units or between noise-sensitive areas, architects and designers must have a general knowledge of the principles of sound transmission and provide proper design to mitigate any noise issues.
As seen from the test results discussed earlier, paying attention to a small detailing increased the acoustic privacy significantly. We are living in times where designers must pay adequate attention to acoustical comfort. During the design stage, there are several options for controlling noise transmission and some options may be rejected due to the requirements of different disciplines. It is during this stage where other options can be discussed, designed, and implemented on-site.
It should be noted that in addition to noise transmission between dwelling, attention shall be paid to intrusive noise aircraft and road traffic, recreational noise, etc. An ounce of prevention is worth a pound of cure. Although perimeter and flanking strips are important it is the noise that travels through the structure that is more important to treat. Hush got a call from an architects practice on the South Coast of England to help assist with a failed Sound Test.
An architect had specified a dividing wall construction to separate two residential units within an existing building. As the existing building was being converted into separate residential dwellings it had to comply with the Material Change of Use Standards of Approved Document E. The architect had specified a twin stud wall construction to divide the two residential units.
The wall construction was constructed on the existing ground floor screed. The wall construction that was specified was a twin timber stud construction comprising of two frames of mm stud work, a clear cavity between the stu frames, an insulation infill within either frame and two layers of Soundbloc Plasterboard on either side of the wall construction. This type of wall construction is standard and should have easily achieved the requirements of the Building Regulations.
It was a dramatic failure by 12 dB. We found out from the test that the wall construction was actually performing well but noise was bypassing the wall construction and was traveling though the ground floor screed.
This was an in-direct sound path flanking path causing the wall to fail a test.
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