Understanding Acoustics in Glass Walls
Have you ever had a extensive conversation about acoustics & what it really involves? I am not talking about all the printed “technical” facts & brochures that we are handed but rather discussions about the true properties of an installed office wall product? I’ve had so many discussions about this subject throughout my career & I wanted to explain in laymen terms what to trust, practice & discuss as to what effects true acoustics but first let’s understand the basic “technical” definitions of the acronyms “STC” & “NRC”:
(As per Wikipedia.org)
· STC stands for: Sound Transmission Class (or STC) is an integer rating of how well a building partition attenuates airborne sound. In the US, it is widely used to rate interior partitions, ceilings, floors, doors, windows, and exterior wall configurations.
· NRC stands for: A Noise Reduction Coefficient is an average rating of how much sound an acoustic product can absorb. (How much quieter a product can make your space.) Like a sponge absorbs water, an acoustic product absorbs sound, and the NRC tells us just how much sound those products can soak up.
Prior to understanding why, I became “An Ambassador of Great Products” or why I live by the phrase “Quality over Quantity” is that for many years I was a buyer & installer of many manufactured glass walls and I’ve come to learn that not all are the same – not even close. Like many others I have managed & installed thousands of linear feet of floor to ceiling cubicle partitions to single or doubled demountable glass walls & moveable glass/wood walls. The most important thing asked of me other than "what’s the LF cost" was the tell me what the “acoustics” is. So, how well do you really know acoustics and what discussions can you have about it? Like most, we are trained to plagiarize brochures & manuals but what I found was that this isn’t a great idea because not all products are tested correctly or if at all.
My entire life belief was to “practice what you preach” and trying to answer that straight faced question “What’s that products STC”?, is daunting. Well without having the fear of misleading the listener & have it backfire on me; I've always explained it as – it's either “has none” or here is the “tested rating” as per the manufacturer, of course. The problem is that the published rating isn’t always accurate and can be misleading because no one truly understands the difference between a sound room tested product and where it’s installed, and the answer is merely explained within the simple means & methods of basic construction.
An example RFQ & issues that arise and/or are missed.
We all get this call, “I need a budget for 5 floors for a single glazed glass wall with a high STC", need it ASAP!
· The Scope: job is located on floors 2nd thru 5th in a high-rise off Broadway near Wall Street - NYC. It’s a trading floor with open cubicles, open ceilings & open stairways & the offices are 9’W x 10’H - The dream project!!
At this very moment I say to myself, YES! What an awesome opportunity, let me get this going quickly. You win the job, install the 4 floors of glass walls and everything goes well, small punch list – perfect! What might happen next is freighting & it's happens often. What do you do when you get the call a few months later from the end user who says “Is this product really rated a 38 because I’ll tell you we can hear every single word between the office walls/spaces. Well - What do we do now, the questions starting swirling in our heads…
· Was the product really tested by a certified testing facility & can we prove it?
· The brochure said it was?
· How about the response “it’s as good as the glass”?, lol
· What discussions should I have had that would properly explain the difference between the certified tested rating vs. the installed product & what can affect it?
This now has the potential of crashing down. Before you jump so quickly have that extended conversation with your audience about it and educate everyone what to really expect - post install. There are so many questions you could have asked when that scope came in.
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The difference between a certified sound room tested rating vs. what’s installed.
To achieve a rating from these certified testing facilities you will need to build your product in their facility within a soundproof room with very sensitive equipment. It’s much different from a job site, trust me.
When a reputable manufacturer tests their products which is set to be marketed with high acoustics they do 3 things, they test the door only, the door & sidelite & the sidelite only. When you test these 3 elevations separately you will find that not all 3 are recorded the same, they all have different ratings. Based on that - Do we really know which rating ones publishes, most times no & usually it’s the highest number. Not very convincing right?
I don’t do that; I never discuss the rating because it’s never real, it like taking about linear foot costs – it’s not real – it’s merely a scale & changes often. The job site isn’t a soundproof room. Shocking, no? I start by discussing the traits of people & the construction of the space and room. This is what will determine a good & true STC.
· What type of room are the demountable walls being installed into?
· Are the walls insulated, are they single or double sheet rocked, do they go way up to the deck, or do they stop just above the acoustic ceiling?
· Is there a raised floor or adequate soundproof flooring?
· Does the HVAC duct run from room to room or room to hallway?
· Who is sitting in the room or area? are they verbally loud or soft spoken?
All of these questions above effect acoustics head on, so in other words if these items are not fulfilled or corrected or built as good as the glass wall then no one should care what you install in the opening, you will not get the rating you were asking for.
So as a conclusion, have those conversations and ask those questions because our biggest fear and regret is that the customer thinks they did not get what they were told because they knew nothing about the difference between a sound room tested product vs what’s to expect post install.
Joseph P. Iannici
Sales Director - Eastern Region
Mobile: 1-646-678-1766
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