Dispelling the Seven Myths of Sound Isolation

Dispelling the Seven Myths of Sound Isolation

What to know from the “INCE Building Acoustics Webinar”

It is said that “silence is golden.” For those living with noisy neighbors or loud, nearby businesses – silence is also elusive. The solutions to these noise problems can be equally elusive.  Many myths have been bantered about around noise control and sound isolation.

Felicia Doggett, INCE Bd. Cert. President, CEO, and Founder of Metropolitan Acoustics and Benjamin Davenny, PE, INCE Bd Cert, EDAC, Health Care Market Leader and Principal Consultant at Acentech shared the seven sound isolation myths at a recent INCE webinar.  Here’s what they had to say. The full webinar is available for free on the INCE website.

 

Myth #1: Wood studs and heavy gauge structural studs are good for isolation.

Truth: The stiffer the stud, the more sound energy transmits through.

Think of it this way. You’re back in your childhood, playing telephone with your friends by using two tin cans and a string. If you and your friend have slack in the string, you can’t hear as well. While it may be good to hear your friend, it won’t be as nice to hear all the surrounding noises in the building that you’re in.

We’d recommend using light gauge studs as lighter gauge studs are more flexible and reduce sound energy. Another option is the use of resilient channels or isolation clips.

 

Myth #2: Putting acoustic panels on walls can increase isolation.

Truth: Because acoustic panels are porous and lightweight, they do not block sound.

While acoustic panels absorb sound due to the porosity, they don’t block sound and are best used for reducing reverberation or echoes in a space.

Instead of putting acoustic panels on walls to increase isolation, the best method is to increase the mass. This means adding more drywall, as it blocks sound and improves isolation. In addition to adding mass, the use of resilient connections and absorption in the cavity are all components of improving isolation of a wall.

 

Myth #3: Putting curtains on windows will decrease the sound coming through.

Truth: Curtains do not have much mass, and do not stop sound from coming through them.

Similarly to acoustic panels, curtains are not designed or used in best practice to stop sound. More importantly, they do not form a complete enclosure over a window or space, so sound is able to go around them, thus propagating into the space you are trying to keep quiet. Again, similarly to acoustic panels, curtains do absorb sound within a space, lessening the echo and reverberation.

When looking to reduce sound coming through windows, the best method is to add more mass, just as you would with drywall, except this time we recommend using an interior storm window spaced at least 2” or more from the existing windowpane. Air space between the two panes is especially good at reducing low-frequency sounds in space.

 

Myth #4: Spraying the underside of a concrete deck will increase sound isolation.

Truth: Acoustic spray is intended to reduce reverberant buildup, not stop sound.

As the truth states, and similarly to walls and windows with absorptive panels and curtains, a spray is not the way to go when it comes to preventing sound transmission through a deck. While absorptive spray is lightweight and porous, it will only reduce reverberant buildup, but it will not stop the sound from coming through.

There’s a common theme to solutions and truths when it comes to sound isolation, and that’s using mass, resilient connections, and absorptive insulation in the cavity to improve sound isolation. Best case for a concrete deck? Use a resiliently suspended gypsum board barrier ceiling hung below the joists.

 

Myth #5: Adding insulation (sprayed or otherwise) into a wall or floor/ceiling cavity will improve isolation.

Truth: If the ceiling is attached directly to the bottom of the joists, sound will transmit through them, bypassing the insulation.

The truth sums this myth up well, but this is especially true for impact noise. You need to use both insulation and resilient connections to improve isolation – using one or the other is not sufficient.

 

Myth #6: Concrete floor slabs are all you need for good sound isolation (watch the impact noise).

Truth: Concrete slabs are very massive and good for airborne sound isolation but not necessarily good for impact isolation.

Concrete slabs transmit impact noise fairly efficiently as they are very stiff and monolithic and are best served at stopping airborne sounds like conversation. Concrete floors should have a resilient underlayment between the finished floor and the concrete slab to reduce impact sound transmission.

 

Myth #7: Carpeting will solve all your noise problems.

Truth: Carpet noise will reduce higher frequency impact noise, but not low-frequency impact sounds.

Carpeting is great for impact sound reduction, but not necessarily for wood frame construction. Wood frame construction can be very thumpy when walked on due to its lightweight nature. You need to stiffen up the structure by using mass – often with gypsum concrete – to improve both airborne and impact isolation.

 

We hope the dispelling of these myths help you improve your noise control and better isolate sound, and if you have any questions, or would like to learn more about noise control, we invite you to visit our website’s Conferences Page, which has the upcoming conferences and events that INCE-USA will be speaking at.

 

Sustaining Members

  • Herrick
  • Scantek
  • CGA
  • NCE
  • ECORE
  • PSU
  • Illingworth
  • Wilson Ihrig
  • CT
  • Kolano and Saha Engineers, Inc.
  • CDM Stravitec
  • SVI Dynamics Logo small