Those Pesky Neighbors…

We’ve all been in scenarios where we have heard unwanted noises leaking into the rooms we’re occupying. In the business world, this might come during an important meeting in the conference room when you’re with a client and the company clown tells a joke outside the door and everyone laughs except for you; the one giving a presentation. Or for a recent partner, hosting a meeting when classes end and a stampede of college students pass on the floor above. Most of the time it’s not difficult to determine what the noise is that’s entering the space, but it is hard to figure out how to stop it. To get you pointed in the right direction, let’s first understand how noise can travel and then where to look to solve it.

In general, sound travels into your space either through the air or by vibrations started from an impact. Spoken words, loud music, or a ding from a microwave, are all examples of airborne noise. Each sound is created with many frequencies that travel through the air at the same speed, but a different amplitudes (volume). The question is, what happens to those frequencies when they run into something like a wall, door, or ceiling? Well, it all depends on the materials, air gap, insulation, and thickness of the barrier as they all play a part in attenuating the different frequencies that pass through. High frequencies can be blocked or attenuated by basic wall construction. However, with low frequencies (long wave forms), required thicker, denser, or larger barriers to stop the sound from getting through. Think of it like Chuck Norris karate kicking through the barrier. A thin wall with little density is no match for the master. But something with multiple layers of drywall, or solid block, might make it a bit tougher (though Chuck Norris can roundhouse kick through anything!) In general, the more mass you have, the better chance you have at stopping all frequencies of the noise.

The second type of noise transmission is through vibration of materials. This is what you hear when the basketball team is practicing above you. What happens is that the ball (source) impacts the floor causing it to vibrate. The floor material then passes that vibration into the joist or other structural element, which could then pass it to the ceilings or walls of your space. These surfaces then tend to act like loudspeakers, vibrating and producing the noise in your room. Vibrational noises can even come from devices that are attached to walls and excite the structure, like a hand dryer or exhaust fan.

Some vibration issues can be easily fixed by placing a thick rug where people are walking. However, most vibration noise issues are much tougher to eliminate as you have to find a way to isolate the materials. The best time to work through this is during new construction when it’s easiest to include isolators or floor treatments that will reduce or eliminate the hand off of vibrations. If you’re already well past that point, then having the space evaluated and setting expectations is suggested so that if a renovation is needed, it takes care of the issue the first time.

For both airborne and vibrational issues, there are tests that can be performed to get a baseline of how the construction is performing. This allows designers to determine what the best next steps are and can help guide you into making the most worthwhile choice for your space. If we find that a wall isn’t performing as it should be, it might be that there are gaps, cracks, or openings in the barrier that need attention. Or possibly that the current construction just isn’t correct for what your goal is of the space. Hopefully it will be an easy fix, but if not, at least you have a better sense of why unwelcomed noises can be so troublesome and why the solution may not be an obvious one!

Kevin Watson, CTS-D

Kevin Watson is currently an AVL-Engineer for ESCO Communications and brings 12 years of experience in AV system design and acoustics. His certifications include a CTS-D (Certified Technology Specialist in Design) from Avixa (new name for InfoComm International) and an EIT (Engineer in Training) by National Council of Examiners for Engineering and Surveying (NCEES).

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