Does Wall Insulation Reduce Noise?

If you’ve ever been distracted by muffled voices through a wall or the persistent hum of traffic outside, you’re not alone. In homes, workplaces, and multi-unit dwellings, unwanted noise is one of the most common—and most overlooked—comfort issues. While most people associate insulation with keeping in warmth, the right kind of wall insulation can also soften the impact of sound.

But how exactly does it work? And can it really make a noticeable difference?

What Happens When Sound Hits a Wall?

To understand how insulation can help, it’s useful to know how sound behaves. Sound waves are vibrations that travel through air and solid materials. When these waves strike a wall, they can be:

• Reflected back into the space,
  
  
• Absorbed by the material they hit, or
  
  
• Transmitted through to the other side.

Traditional walls—especially those with no cavity insulation—tend to transmit sound more easily. That’s where insulation steps in: it works by disrupting the transmission of sound energy and dampening internal vibrations within the wall structure.

Can Insulation Really Reduce Noise?

Yes—quite substantially, depending on the construction of the wall and the insulation you select. In building science, this effect is typically measured using the Sound Transmission Class (STC) rating. A higher STC number means better sound isolation.

For context:

• A basic, uninsulated interior wall has an STC rating around 33. This allows most speech and ambient noise to pass through clearly.
  
  
• Adding good acoustic insulation, such as Premier 100% Polyester Acoustic Wall & mid-Floor blanket, or Premier Glasswool Thermal & Acoustic or Mid-Floor blanket, can boost this rating to 45 or higher—enough to reduce loud voices to a slight murmur.
  
  
• Additional strategies, like using resilient channels or double layers of plasterboard, can push STC ratings beyond 50, which is considered excellent sound control.

Which Insulation Materials Work Best?

Thickness and density are important to noise reduction.  Insulation should ideally fill the cavity and higher-density is better.

• Premier Glasswool Insulation
  Glasswool is the most common insulation material used in NZ.  It is cost-effective and will perform very well in walls and mid-floors to reduce and control noise.
  
  
• Premier 100% Polyester Insulation
  Known for being low-irritant, safe to handle, and environmentally preferable, Premier polyester products offer a unique blend of polyester fibres that maximise absorption creating quieter, more peaceful living spaces.
  
  

Don’t overlook those gaps and cracks in your walls—around outlets, windows, or between studs—because they can let sound through. Sealing these spots when you’re installing insulation really makes a difference.

So, is it worth it? 

If you like having some peace and quiet, then definitely—wall insulation helps keep the noise down. Research from BRANZ shows that well-insulated homes have better satisfaction with temperature and noise levels.

And it’s not just about comfort. Better sound control can boost your property value, reduce complaints from neighbors, and help you sleep better.

In short, wall insulation isn’t just for keeping warm. When done right, it blocks both cold air and noise. Whether you’re building new or upgrading, making smart insulation choices can create a quieter, more comfortable home.

If you need help picking the right insulation for noise control, reach out to a pro at Premier Insulation. We have options for homes all over New Zealand and can help you find something that fits your needs.