• Fan noise transmission: supply or return paths carrying sound directly into occupied rooms.
• Cross-talk: voices and activity traveling between rooms through duct runs.
• Rumble and low-frequency components: often tied to vibration, velocity, and system balance.
• Breakout noise: the duct radiates sound through ceilings and walls.

We design duct noise control so the HVAC system still functions correctly. Typical strategies include:

• Duct silencers and attenuators: used where fan noise is transmitted down the line.
• Acoustic lining where appropriate: to reduce internal reflection and breakout.
• Sound mazes / plenum strategies: to block direct line-of-sight transmission while maintaining airflow.
• Vibration isolation at connections: because vibration can excite duct walls and create breakout noise.
• Penetration sealing: airtightness matters—sound rides on air leaks.

If the duct is above a sensitive room, the receiving condition may also require ceiling soundproofing.

In some buildings, ductwork and piping run through warm mechanical zones and shafts. When durability and temperature stability matter, we use heat-appropriate detailing:

• Foil-faced insulation systems: to maintain performance and cleanability over time.
• Sealed jacketing and continuity: so the system remains intact through maintenance cycles.
• Damping where needed: to reduce panel resonance and metal “ring” on large duct faces.

Can I just add insulation around the duct? Sometimes it helps, but duct noise often needs internal attenuation (silencers/lining) plus vibration control and airtightness.

Why can I hear conversations through the vent? Cross-talk through shared duct paths is common. It requires a designed break in the sound path, not a cosmetic grille change.

Related mechanical systems:

• HVAC Unit Soundproofing
• Pump Soundproofing
• Chiller Soundproofing

External references (authority):

• ASHRAE: Noise and Vibration Control
• WBDG: UFC 3-450-01