Let’s say you’ve designed an acoustically perfect home or office, but your HVAC system is letting you down. When tackling this kind of noise pollution, you might ask “what is acoustic duct liner?”

Acoustic duct liner is a specialized solution for the problem of noise from the metal duct network of an HVAC system. 

In this article, we will discuss what this product is, how it works, how you can install it, and the best acoustic duct liner for your needs…

Skip to:

• What is acoustic duct liner?
• How does acoustic duct liner work?
• Installation guide
• The best acoustic duct liner
• Regulatory and performance standards

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What is acoustic duct liner?

An often-overlooked source of indoor noise is a building’s HVAC (Heating, Ventilation, and Air Conditioning) system. 

The network of metal ducts that distribute air throughout a structure can become efficient conductors of unwanted sound – from mechanical equipment noise to cross-talk between rooms. 

Acoustic duct liner represents a specialized solution to this problem, offering a way to reduce noise transmission while maintaining proper airflow:

Acoustic duct liner is a specialized material installed inside HVAC ductwork to absorb sound energy and reduce noise throughout a building’s ventilation system. 

It is typically manufactured from fibrous or porous materials. In this way, acoustic liners transform sound energy into heat through friction within the material’s microstructure. This is great, because it dampens noise at its source and along transmission paths. The result is a quieter home and office – job done.

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How does acoustic duct liner work?

Why does acoustic duct liner make sense for soundproofing? The fundamental principles comes down to sound physics and material science. 

So here are the clever bits to our mini guide. In this section, we dip into the science of acoustic duct liners

Sound absorption mechanisms

When sound waves hit acoustic duct liner, several processes happen at once:

1. Viscous dissipation 

As sound waves move through the small pores and passages within the liner material, friction between air molecules and the material’s fibers converts acoustic energy into heat.

2. Thermal exchange

Sound waves create minute pressure variations, which produce temperature fluctuations. The liner material absorbs this thermal energy, further reducing sound intensity.

3. Structural resonance

The fibers or structure of the liner material vibrate in response to sound waves, converting acoustic energy into mechanical energy that ultimately dissipates as heat.

Basically, the porosity, density, thickness, and fiber structure of the liner material will determine its effectiveness across different sound frequencies. So to ensure you get this absolutely right, you’ll need to determine which sounds are causing the disturbances…

Frequency response characteristics

Acoustic performance varies significantly across the sound spectrum:

• Low-frequency sounds (below 500 Hz)

 These bass frequencies with long wavelengths typically require thicker materials or specialized designs to absorb effectively. Standard liners often have limited effectiveness in this range.

• Mid-frequency sounds (500-2000 Hz)

Most conventional duct liners perform efficiently in this range, which encompasses many common mechanical and voice frequencies.

High-frequency sounds (above 2000 Hz)

These shorter wavelengths are relatively easy to absorb with even thin acoustic materials, allowing for efficient treatment of higher-pitched mechanical noises.

You’ll select specific liner types and thicknesses based on the target frequency range needed. Don’t worry, most liner types will specify the frequencies they are most effective against.

Did you know? Acoustic duct liner is also effective in providing thermal insulation, making it a great dual-benefit option for energy efficient buildings.

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Installation guide

Here is a step-by-step guide on how to install acoustic duct liner to reduce noise disturbance:

👉 Step 1: Gather your tools and materials

Before you start, make sure you have everything you need:

• Acoustic duct liner (usually made from fiberglass or foam)
• Measuring tape
• Utility knife or scissors (for cutting the liner)
• Duct adhesive or foil tape
• Gloves and safety glasses
• Respirator mask (if you’re working with fiberglass materials)
• Duct supports (if needed for extra stability)

👉 Step 2: Measure the ducts

The first thing you need to do is measure the ductwork where the liner will go. 

Take your measuring tape and measure the length, width, and height of the duct. For round ducts, measure the diameter. Write down these measurements because you’ll need them when cutting the acoustic liner.

👉Step 3: Cut the acoustic liner

Now it’s time to cut the acoustic liner to fit your ducts. Lay the liner flat on a clean surface, and using your measurements, mark where you need to cut. Use a utility knife or a pair of scissors (depending on the type of liner you’re using) to carefully cut along the marked lines. It’s important to cut the liner slightly larger than the duct dimensions so that it fits snugly inside.

👉 Step 4: Apply adhesive or tape to the duct

Once your liner pieces are ready, the next step is to prepare the ducts. If you’re using adhesive, apply it evenly along the inside of the duct where the liner will be placed. If you’re using foil tape, make sure the surface is clean, then apply the tape where the liner will attach.

👉 Step 5: Install the acoustic liner

Carefully insert the cut liner into the duct. Start at one end of the duct and work your way to the other end, making sure it fits snugly. Press the liner against the sides of the duct to ensure it sticks to the adhesive or tape. If the liner doesn’t fit perfectly, trim the edges as needed.

👉 Step 6: Secure the liner

Once the liner is in place, you’ll need to secure it so that it doesn’t move over time. If necessary, use additional adhesive or tape to keep the liner firmly in place. For larger ducts, you may want to install duct supports to keep everything stable, especially if the liner starts to sag.

👉 Step 7: Check for gaps and adjust

After installing the liner, check the duct for any gaps or loose spots. Any space where air can escape will affect the performance of the liner. If you find any gaps, use more adhesive or tape to seal them. Ensure that the liner is completely secure before moving on.

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The best acoustic duct liner 

The market offers several categories of acoustic duct liner, each with distinct properties suitable for different applications.

Fiberglass remains the most widely used duct liner material, combining excellent acoustic properties with cost-effectiveness. These products consist of inorganic glass fibers bonded with thermosetting resins and typically feature a protective airstream surface to prevent fiber erosion.

Standard fiberglass duct liners come in densities ranging from 1.5 to 3 pounds per cubic foot (pcf), with higher densities generally providing better acoustic performance. 

We’ve picked out this acoustic duct liner on Amazon as an excellent value option for noise absorption:

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Regulatory and performance standards

Acoustic duct liners must comply with various industry standards and building codes. Click on the hyperlinks below to read the full regulations:

• ASTM C1071: Standard specification for fibrous glass duct lining insulation
• ASTM E84: Surface burning characteristics (flame spread and smoke development)
• UL 181: Factory-made air duct materials and air duct connectors
• NFPA 90A: Standard for the installation of air-conditioning and ventilating systems
• ASHRAE Standard 62.1: Ventilation for acceptable indoor air quality

These standards ensure that installed materials meet minimum performance requirements for safety, durability, and acoustic effectiveness.