Why doesn’t my wall stop the noise?

Why doesn’t my wall stop the noise?

Did you know that sound leaks can destroy the soundproofing of a wall?  If the wall leaks, it won’t work. What is a sound leak?  A sound leak is any gap or hole in a wall where air can pass through.  If air can get through, noise will get through.  So what? A gap that is equal to 1% of the wall area can lower the Sound Transmission Class of a partition from STC 50 to STC 40.  A reduction of 10 STC points means the sound coming through the wall seems about twice as loud.  A 1% gap is less than 1/8” wide across the bottom of a typical apartment wall. So what should you do about it? Any hole, gap, or joint must be sealed airtight.  Gaps often occur where the wall meets the floor and the ceiling, around pipes, ducts, and conduits, and around joists or beams that cross the wall.  Acoustical engineers usually recommend non-hardening sealants because other sealants will crack over time. Make sure that you get the sound isolation that you expect and pay for.  Specify that the wall be sealed well on both sides.  ASTM C919 Standard Practice for Use of Sealants in Acoustical Applications contains additional information....
What Makes Better Neighbors?  Better Sound Isolation of Course.

What Makes Better Neighbors? Better Sound Isolation of Course.

Residents with poor sound isolation are more likely to want to move, have their sleep disturbed, and to think their neighbors are inconsiderate.  That’s what a detailed Canadian survey of townhome and multi-story apartment building residents found. Acoustic engineers evaluated the apparent Sound Transmission Class (STC) of the party walls and found that resident’s desire to move dropped significantly as the STC rating and soundproofing increased. Satisfaction with sound isolation begins with walls above STC 50 and continues to improve as the STC rating increases. Increase the satisfaction and retention rate of your tenants…current and future.  Call or email us to discuss your building! Reference:  “Deriving Acceptable Values for Party Wall Sound Insulation from Survey Results”, J.S. Bradley, Inter-Noise 2001 Proceedings, The Hague, The Netherlands, 2001....
The Impact of a Poorly Isolated Floor

The Impact of a Poorly Isolated Floor

Do you need an IIC test? Do your tenants complain of hearing their neighbors above?  Does your old building meet modern building codes for sound isolation?  Do you want to make sure that you have the sound isolation that you paid for?  Maybe you need an IIC test. What is an IIC rating? The IIC (Impact Insulation Class) is a rating of the impact sound on a floor that is audible in the room below.  A higher number means better impact sound insulation. What is an IIC test? An IIC test is done by an acoustic engineer using ASTM Standard E1007 – Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures.   The test can determine the IIC of the floor-ceiling that separates condominiums, apartments, or offices. How is an IIC test done? The test requires access to the both rooms – the one above the floor and the one below.  A standard tapping machine bangs on the floor to generate impact sound (see ours in action).  First, while the tapping machine is banging away, the sound level is measured in the room below.  This is repeated with the machine in four different positions on the floor. Then the reverberation time, or T60, is measured in the room below.   The T60 is used in IIC calculation to “normalize” the measurements to a standard condition.  This allows us to compare an IIC measured in a “dead” room to one measured in a “live” room. Next, the airborne sound isolation of the floor-ceiling is measured.  Usually a loudspeaker and amplifier generate pink...
What’s a Tapping Machine?

What’s a Tapping Machine?

The new Tapping Machine is here!  The new tapping machine is here! Okay, maybe you’re not an Acoustic Engineer and not as excited as I am, but just look at this beauty in action. What is a tapping machine?  It’s only purpose in the world is to measure the Impact Insulation Class (IIC) of a floor-ceiling.  The IIC is a measure of how much you hear someone walking around in the condominium or apartment above you.  The machine bangs on the floor by dropping five metal “hammers” over and over again.  If you look close you can see the hammers dropping under the machine. The weight of the hammers, the hammer spacing, the height from which they are dropped, and the time between impacts are all defined in ASTM Standards E492 and E1007, and ISO Standard 140-6.  ASTM E1007 is the Standard Test Method for Field Measurement of Tapping Machine Impact Sound Transmission Through Floor-Ceiling Assemblies and Associated Support Structures.  This is the standard we use to do field tests in apartments, condos, and other buildings. Now don’t you wish you had a tapping...
How Can I Improve The Sound Transmission Class Of A Wall?

How Can I Improve The Sound Transmission Class Of A Wall?

That depends….on many different things.  Some are obvious, some are not. The Sound Transmission Class (STC) is a rating of airborne sound insulation.  The STC is good at rating sound isolation when the sound is a person speaking, but has limitations when used for sound with lots of low frequency energy, like music.  It is important to understand that the STC of a wall depends on the entire wall assembly….how many layers of drywall?…how thick are the studs?…is there insulation in the wall cavity? However, there are less obvious things that affect a wall’s STC.  Here are a few things you may not have realized. using light gauge steel studs can give you a much higher STC than using wood studs or heavy gauge metal studs. studs spaced 24″ on center will perform better (with a higher STC) than studs 16″ on center. with a double stud wall (two separate rows of studs), placing two layers of gypsum board on each side of the wall (four layers total) is better than placing one layer on each side of each row of studs (same four layers total).  Usually the STC will be higher, and low frequency sound isolation will be better. The STC of individual components of a wall cannot be added together.  The rating of the assembly depends on how the components work together.  When evaluating the STC  of an assembly, remember to consider the entire assembly, not just individual...
What Is My Floor’s Impact Insulation Class (IIC)?

What Is My Floor’s Impact Insulation Class (IIC)?

Impact Insulation Class, or IIC, is a rating of impact sound insulation. Impact sound is the sound of impact on a floor surface, like the sound of footsteps on the floor above. It only applies to sound transmitted down through a floor and ceiling. It does not apply to walls.  The International Building Code (IBC) requires that a floor-ceiling separating condominiums, apartments, hotel rooms, or other dwelling units be designed for an IIC of 50 or higher.  If the floor-ceiling is tested in the field, a field IIC, or FIIC is allowed to be 45 or higher. I’m often asked “What product will achieve an IIC 50?”  IIC ratings can be confusing.  Information published by floor product manufacturers can be even more confusing. One way to increase a floor-ceiling assembly’s IIC rating is to put a “soft” underlayment under a hard floor.  For example, there are many resilient mats that are designed to be placed under ceramic tile, under wood laminate, or under vinyl flooring. The most important thing to remember is that none of these products have an IIC rating by themselves.  The IIC rating is a rating of the entire assembly.  If you are considering the IIC rating of a tile floor on a resilient mat underlayment with a gypsum board ceiling below, the rating is dependent on all of these components.   What is the subfloor?  …plywood (one layer or two)? …gypsum concrete (how thick)? … concrete?  These things make a big difference.  How is the gypsum board ceiling mounted? …directly on joists? …on resilient channels? …on resilient clips?  This makes a big difference too. A common mistake is...