For those of us in the construction and furniture industries avoiding STC’s is often a challenge. Once contracted they are difficult to get rid of and quickly become resistant to most known treatments. If you’re not involved in furniture or construction, read on, so you are able to recognize the symptomology in friends, loved ones or yourself should the infection of STC’s spread.
STC stands for ‘Sound Transmission Class’ and is not a medical condition, but a methodology for measuring the amount of sound transmitted through something – in the case of construction, usually a wall; in the case of furniture, that something is a panel or partition that divides a space. STC measurements usually range from 25 to 72 and are established based on testing results performed in a laboratory.
Say I told you it was 10 degrees Celsius (50 degrees Fahrenheit for our American friends) outside. You’d know exactly how warm/cold that is and you would dress accordingly. This system works precisely because it is a universally accepted measure that has been consistently applied for generations. Now, say I told you I was going to build you an office with an STC rating of 30. You likely wouldn’t have a clue as to what that means. Even if I told you it would be acoustically appropriate for your needs you wouldn’t know if I was telling the truth or not.
Ah, but you’re a resourceful lot and you do some research. You now know that the onset of “Privacy” does not occur below an STC rating of at least 40. Say you call my bluff, so I add some insulation or other technology, not to mention an increase in price, to my solution in order to get you that coveted score.
We build the office, and guess what? You can hear your neighbours’ voices even if you can’t make out what they’re saying. You can hear the music from the restaurant downstairs, the buildings mechanical noise, even traffic outside. Not what you were expecting.
So what went wrong? For starters that STC rating was tested in a laboratory environment that did not take into account “other” factors or sound frequencies outside of a 125 Hz – 4,000 Hz range. The rating likely did not take into account the doorway (did you really need that option?), windows, electrical outlets or other breaches in the wall and how they were not sealed. It did not take into account the acoustical properties of the ceiling or floor.
An STC rating is a number that is often thrown down like a gauntlet, a challenge to see who can offer the highest number. What STC ratings can’t do is inform you fully about what your environment is going to feel and sound like once it’s built. You’re asking for the measurement of something that does not yet exist. That’s like trying to determine the quality of a future model cars ride by telling you that the tires will hold 50 PSI (pounds per square inch) = 340 kPa (kilopascals).
Realistically, all aspects of the built environment and exterior environment need to be considered. Second, even though it is possible to measure most of these factors, it is often not practical or possible, especially when new methods or techniques of building are being contemplated.
So is there a cure? As with any disorder, the best course of action is to be proactive first, and to use common sense:
- If it (the STC rating) sounds too good to be true it probably isn’t.
- Visit a similar environment and see/hear for yourself.
- Deal with reputable builders and manufacturers who can credibly back up what they say and be prepared to challenge their claims.
- Go to the source. Visit the manufacturer/builder to see how it’s built and what’s really behind that pretty finish.
- Be prepared to pay for quality, go beyond base grade specifications and finishes. You’ll get a lot higher level of performance and future proofing.
This may not be a guaranteed cure for STC’s, but it’s better than the alternative mathematical suppository.
Hope you’re feeling better soon.