Mike Holmes is one of Canada’s most respected contractors and TV personalities. He is known by the slogan “Make it right”. I am a fan of his, he really knows renovations and he describes his approach well in his book. He is not a soundproofing contractor, yet, he promotes soundproofing myths.
However, his knowledge of soundproofing has many gaps. He is not a soundproofing contractor, nor he claims being one. He has several articles and YouTube videos where he dispenses soundproofing advice. In his recent article in the National Post he propagates not less than six soundproofing myths that circulate on the Internet. Many so-called soundproofing contractors pickup similar myths.
The sentences in quotes are almost verbatim from the noted article.
Soundproofing myth #1:
Fact: Adding a reasonable amount of sound absorption in a typical residential room has only a small effect on noise level in that room. Hardly worth the effort as documented in reference .
Fact: This is not correct, because there are gaps between the wall and the furniture. These gaps, and the fact that you cannot cover the whole wall, negates the effect of noise reduction . The only exception is a built-in furniture covering the entire wall that is sealed against the wall. Then the noise reduction can be noticeable to significant, depending on how the furniture is constructed.
Soundproofing Myth #3:
“Carpets can reduce noise from downstairs neighbours”.
Fact: The only way that sound attenuation of a floor can be increased is by adding mass to the floor that significantly increases (doubles of more) the mass of the existing floor . Carpet and underlayment certainly cannot do it in most situations.
“Insulation in walls helps a lot”.
Fact: This is the most common misconception promoted by many a soundproofing contractor. Adding insulation to an existing hollow wall reduces the sound reduction only a little. For example, if you add insulation to a standard wall with 3.5” wood studs and 5/8” drywall on each side, the STC value is increased from STC 32 to STC 36 , a modest improvement, insufficient in most situation.
Soundproofing myth #5:
“Sound reducing drywall is as good as 8 layers of regular drywall”.
Fact: This is a widely circulated myth, probably originated by a manufacturer of sound reducing drywall. It is meaningless to evaluate a noise reduction of a sheet of drywall, any type of drywall, because it is only used in assemblies.
As an example, enhancing sound attenuation of an existing wall consisting of 3.5” steel studs on 24” centers and insulation in cavities. If you replace a standard drywall on one side of this wall, with a sound reducing drywall, the STC value will increase from STC 38  to STC 52 . The same wall, but with two layers of standard drywall on each side, provides STC 54 . You get better result with adding a new sheets of drywall on each side, than replacing one sheet with sound reducing drywall. Where is the myth of 8 sheets coming from? If you know, submit the feedback form at the end of this article.
“Adding blown in cellulose insulation into walls adds a lot of echo-dampening power”.
Fact: I am not sure what “echo dampening power” means, but I do not recommend blowing insulation into existing walls. Many so-called soundproofing contractors recommend it. As explained previously, the effect of insulation in wall cavities is only modest, if the wall is filled perfectly. Perfect fill cannot be guaranteed with blowing insulation into cavities.
In conclusion, you cannot rely on soundproofing advice from a respected celebrity contractor. You should not rely on advice of a so-called soundproofing contractor either. A badly implemented soundproofing project is awfully expensive. The soundproofing contractor does not pay for it, he makes his profit. The customer must live with noise after paying for soundproofing, or rework the soundproofing job, doubling the cost of the project. I have many clients with this unfortunate experience, an example is described in this article.
Good soundproofing advice by a professional building acoustics engineer is not expensive, it should be a part of each well-done soundproofing project. You will find more information about what a soundproofing cosultant does in this article. To reqeust a quote from the author, submit the button below.
I always appreciate a reader's comments. If you have a comment, suggestion or a critique, please submit the form below. Your email address and message are completely private, accessible only by me.