Saturday
Jul172010

Soundproofing Ducts

Acoustic Challenge

Your home furnace is designed to circulate airflow throughout your home to help regulate room temperature.   Noise is generated both by the motor fan noise from the furnace and the air flow noise moving through your duct system.   If your ductwork is undersized based on the power of your furnace system, this increases your velocity pressure as sound waves begin to break out through the walls of your duct system.   Our goal is to protect the rooms in your home from the noisy ducts and furnace noise.

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Soundproofing Treatment

If you are here in advance of new construction or a tear-out remodel project, you can replace standard ductwork with ductwork that is lined on the inside with sound insulation material.   If you are treating existing loud ductwork with no access to the interior of the duct, jacket the exterior of the duct with lagging material designed to hold the noise inside.   Either of these HVAC soundproofing treatments will help contain the noise to within your system and guard against the bleed out through the walls into the room you seek to protect.   Your product options for these treatments are listed in here in our Product Bin, and also featured in our section on Furnace noise in our Applications Guide.

Acoustic Results

By lining either the interior of exterior of your ductwork, you are better able to contain the unwanted sound from air flow noise or motor fan noise that is otherwise breaking out through the walls of your ductwork.   The sound proofing treatment for noisy ducts and ventilation noise can typically trigger an average 10-12 decibel level drop.   These results for soundproofing ducts are simulated in our Sound Chamber for your reference.

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Start Smart:     Good Decision Making Will Save You Money


Making good decisions will save you time and money.   Nothing is more costly or pocketbook-draining than to discover that the wrong product, the wrong treatment, or the mis-installation of your order forces you to start over,  accept inferior results, or suffer from buyer's remorse.


To help avoid missteps and protect your investment, NetWell Noise Control
offers its famous, safe, and secure email course called StartSmart.   It is filled with valuable insider tips on saving money with your soundproofing treatment.   This popular teaching tool is your guide to a successful
soundproofing outcome.   The eCourse is free, and enjoyed by more than
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Sign up today and check your email for StartSmart!

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There are two sources of noise related to your ductwork.   The fan noise generated within the furnace itself, and the noise resulting from constricted airflow hustling through your ductwork.   To quiet your furnace room itself, visit the Furnace section of this website.    Here we deal with the ductwork only.

If your furnace emits a higher velocity of airflow than the diameter of your ductwork wants to allow, you will create noise that will vibrate along the metal surfaces of your ductwork as a result of the constriction of the air movement..   As the metal vibrates, the noise begins to break out through the walls of the duct out into your room.   To treat this, simply wrap NetLag around the duct and seal the wall off.    If your wall is already finished, line the common wall with dB-Bloc, frame out over this surface, and apply a new layer of drywall as outlined in our Walls section of this Applications Guide.   In either case, you will be able to eliminate a good portion of the noise that you will otherwise be exposed to.

For noise bleeding out the mouth of your supply or return vents, consider replacing a section of your ductwork with insulated ductwork lined with fiberglass and designed to control spillage.   Or consider an Induct Silencer designed to allow for the free movement of airflow but will serve to attenuate the noise that wants to bleed out with it.