Tuesday, October 18, 2011

Coordinating Construction Trades to Optimize Noise Control

Coordinating Construction Trades
to Optimize Noise Control
(Why small oversights can destroy noise control performance)
By Harry Alter & Norman Varney

 Let's say your dream listening space has been designed. Great care in the design construction has been taken to ensure  that dynamic range and low-level details are not masked by noise, nor cause distraction. Noises from outside traffic, electrical, HVAC, footfalls, motors, plumbing, etc. have all been considered. You've spared no expense to make sure your critical listening environment is designed for the most realistic experience. Ceiling, walls, doors, and floor systems have been designed to achieve a minimum STC (Sound Transmission Class) performance rating of 60 and IIC (Impact Isolation Class) of 55.  HVAC ducts were designed to make sure the ambient noise levels within the space are quiet to an NC (Noise Criteria) rating of 20. You’ve crossed your T’s and dotted your I’s, there’s nothing left to do…right?  Wrong. Because what happens in the field will determine whether all your hard design work will pay off.

  Planning to reduce potential field problems before they happen is key to your success. So what more do we plan for? First, plan for flanking noise and second, plan for the Trades in the field to work as they usually work. That means that if we want the various Trades in the field to work together and do what needs to be done, we need to provide clear and concise information and instructions (both visually and verbally) to help them through what will probably be a new and atypical construction process for them. We need everybody to understand the goal and how critical each trade is to achieving that goal.   
Here are a few basic examples of how field conditions and flanking noise can affect a room’s final noise performance level:
  1. Poor caulking around the frame of an acoustical door or along gaps at the floor plate can cut a high STC door or wall system in half.
  2. If a high STC wall assembly is built over an OSB or plywood subfloor, the performance level of the wall will (as a result of flanking noise) typically never achieve a STC rating above 50.
  3. The improper installation of plumbing lines thru wall studs and ceiling joists can take the room’s ambient noise level from a quiet NC 20 to a distracting NC 40.
  4. The direction of floor joists relative to a partition wall beneath it will affect the amount of airborne and impact noise flanking through the floor assembly to adjacent rooms.
  5. Lined duct runs alone don’t assure a quiet listening environment. Typical HVAC installations can be very noisy even with lined duct runs.
  6. Using heavy floor toppings such as Gypsum-Concrete can dramatically increase the STC (airborne) performance of a floor system, but can dramatically decrease the IIC (impact; footfall) performance when not properly addressed for noise control.

  And the list goes on. Remember, a little attention to flanking noise and the Trades can go a long way toward solving potential risks in the field. A/V RoomService is committed to making that journey for both you and/or your customer an easy one. Contact us at 740-924-9321 or at www.avroomservice.com
A few of the visible construction designs offered by A/V RoomService, Ltd.