The “Soundproof” Myth
My first wristwatch when I was a kid was a “waterproof” Timex. The TV commercial even featured one strapped to a speedboat propeller. In spite of the march of technology the 21st century has yielded only “water resistant” watches. One simple reason: “waterproof” Timex-es kept getting broken by water pressure at sufficient depth, leading to warranty returns and damage to the brand.
The problem word: In acoustics, the analogous word is “Soundproof”. It makes for compelling marketing: it’s compact and dramatic, and conveys a high degree of sound reduction. The problem is that, as with waterproof watches, people take it quite literally.
“Soundproof” is an auditory mirage: Close a recording studio door, for instance, and we may experience that the sound has completely vanished. It’s actually still there, just reduced below the threshold of hearing or masked by other sounds. The experience is powerful, as if the door intrinsically possesses infinite sound isolation – the ability to completely eliminate ANY sound under ALL circumstances. Nevertheless, under some combination of high sound levels, quiet background, and finite sound isolation, the “soundproof” property evaporates like a mirage. When this occurs, adherents react most often with indignation, denial, or gaslighting – enlightenment is rare.
But wait, there’s more: There’s even a “compound myth” built atop the first: a rating of STC 50 or better is commonly referred to as “soundproof”. What could possibly go wrong? A band director was irate because musicians could be heard through his new music practice rooms’ “soundproof” STC 50 doors which, of course, must be defective.
Myth vs. Reality: I explained to him what STC 50 really means in practice – that a 90 dBA trumpet attenuated maybe 50 dBA would end up about 40 dBA, plainly audible in a quiet band hall, and that the tuba player would be even louder. You could see the gears turning briefly, then human nature intervened and he “recovered” his equilibrium: the band hall design (his) relied entirely on “soundproof” doors, so they must perform! (Of course, he didn’t want to hear about the shared, untreated HVAC ductwork either.) To my knowledge the door manufacturer never got paid, even after numerous futile seal adjustments and onsite tests.
My advice is to banish this word from your vocabulary! If anyone on a project you’re supporting uses it, take action immediately to promote realistic expectations. If that causes you to lose work, it’s probably better than being obliged to deliver a miracle.
Nelson Acoustics has extensive experience assessing and improving the acceptability of products, machines, equipment, facilities, and buildings. For best results noise emission and sound quality can and should be considered at the outset.
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