Does triple glazing stop motorway noise from the M3?

For the constant M3 or A34 'drone', usually no. Standard triple glazing is designed for heat retention. If the glass panes are the same thickness, they can actually vibrate together (resonance), letting low-frequency noise pass through.

What is the best glass for stopping traffic noise?

For replacement windows, you need 'Acoustic Laminate' glass (like Stadip Silence) which uses a plastic interlayer to dampen vibration. However, the ultimate solution is Secondary Glazing with a 100mm+ air gap installed by a specialist.

Do I need planning permission for soundproof windows?

If you use Secondary Glazing, usually no—even in Listed Buildings—because it is reversible and sits inside the property. If you want to replace the windows entirely, you must check if you are in a Conservation Area (like Upper Clatford or Winchester) where Article 4 directions may apply.

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Battling the Traffic Drone: A Local’s Guide to Silencing the A303, A34 & M3

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Battling the Traffic Drone: A Local’s Guide to Silencing the A303, A34 & M3

Battling Traffic Noise: A Local’s Guide to Silencing the A303, M3 & M27 | KJM Group

📍 Winchester 📍 Andover 📍 Salisbury 📍 Basingstoke 📍 Southampton

From the constant hum of the M3 near Winchester to the heavy drone of the A303 past Andover and the M27 corridor in Southampton, our region is defined by its busy transport links. It’s not just traffic; it’s a low-frequency sound wave that standard windows simply cannot block.

🚦 The Hampshire Reality Check

Many new builds across Andover, Basingstoke and Winchester Were fitted with standard “Thermal” double glazing. While excellent for keeping heat in, these units are often acoustically transparent to Heavy Goods Vehicles.

The hard truth: Simply upgrading to standard triple glazing is usually a waste of money for this specific problem.

At KJM Group, we often visit homes where owners have spent thousands on new windows, only to find the 4am lorry noise is exactly the same. This guide explains the physics of sound and how to actually stop it.

1. The Science of Silence: Understanding Decibels

Most people don’t realise that sound is not measured linearly. It is a logarithmic scale. This means a small number change represents a huge physical difference.

-3 dB Just noticeable

-5 dB Clearly quieter

-10 dB Half as loud

The Goal: An open window lets in about 70dB of street noise. Standard old double glazing might reduce this by 25dB. To make a busy road sound like a quiet library, we need to aim for a reduction of 40dB to 50dB.

2. Why Your Current Windows Are Failing

To fix the noise, you first have to diagnose the frequency. As shown on the Defra Strategic Noise Map, major arteries like the A34 and M3 generate a specific sound profile:

High Frequency (Whine): Tyres on wet tarmac, wind noise, sirens. Standard double glazing blocks this reasonably well.
Low Frequency (Drone): HGV engines, exhaust rumble, the steady A303 “hum”. This is a long sound wave that passes straight through standard glass.

💡 The “Triple Glazing Trap”
Standard triple glazing often uses three panes of 4mm glass. Because they are all the same thickness, they vibrate at the same frequency (Sympathetic Resonance). Effectively, the sound wave uses the middle pane as a bridge to cross into your bedroom.

🔊 Tool: The Noise Diagnosis

Answer 2 questions to find your specific fix.

What does the noise sound like?

Are you in a Conservation Area?
(e.g., Winchester City Centre, Salisbury?)

✅ Recommendation: Secondary Glazing

Why: The A303/M3 drone is best killed by a massive air gap (100mm+). Secondary glazing “decouples” the sound.

The Fix: Keep your original timber windows (preserving the look for planners) and install a slimline aluminium unit inside.

Expected Reduction: 50dB+ (Massive difference).

View Secondary Glazing Options →

🛠 Recommendation: Acoustic Laminate Replacement

Why: Since you aren’t restricted by planning, you can replace the frames, but avoid standard triple glazing.

The Fix: You need Asymmetric Glazing (e.g., 6mm Stadip Silence + 4mm standard). The different thicknesses disrupt the sound wave, and the PVB plastic layer absorbs vibration.

Expected Reduction: ~40-42dB (Significant improvement).

Get a Quote for Acoustic Glass →

3. The “Magic 100mm” Air Gap

For residents in historic areas like Salisbury or Winchester, where heritage is key, Secondary Glazing is actually scientifically superior to replacement windows for noise.

Sound waves struggle to jump across large spaces. Double glazing has a gap of 16mm-20mm. Secondary glazing creates a gap of 100mm to 200mm. This “dead air” acts as a massive shock absorber.

Diagram showing the 100mm air gap created by secondary glazing to stop sound

The “Magic 100mm Gap”: Why Secondary Glazing beats Triple Glazing for noise.

Solution	Typical Cost	Noise Reduction (dB)	Real World Feeling
Standard Triple	£££	~32dB	Slightly muted
Acoustic Double	££	~42dB	75% Quieter
Secondary Glazing	£	50dB+	95% Quieter (Library Quiet)

4. A Warning: The Planning Trap

Before you rush to replace your windows, check your postcode. Many parts of Winchester and Salisbury are Conservation Areas, or subject to Article 4 Directions.

In these scenarios, Secondary Glazing is a lifesaver. Because it is installed on the inside of your home, it does not require planning permission in 99% of cases.

Ready to sleep past 5am?

We are a local Hampshire business. We drive the A303, A34 and M3 every day. We know exactly what that noise sounds like, and we know how to stop it.

Book a Free Acoustic Survey

We’ll come out, listen to the noise, and give you an honest solution.

About
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Mark Pearce

With over four decades in the glazing industry, Mark Pearce has been at the heart of KJM Windows & Conservatories since 1983. Starting as a building labourer, he quickly rose through the ranks, working as a window and door installer from 1984, a factory operator manufacturing windows later that year, factory manager in 1992, and joining the sales team in 1994. Becoming a Director in 2002, and finally, the sole owner in 2010, Mark Pearce is truly a double glazing expert and has led KJM to become a leading supplier of high-quality windows, doors, and conservatories across Andover and the South of England.

Mark Pearce is a highly experienced specialist in the double glazing industry, having built his knowledge from the ground up through hands-on experience in installation, manufacturing, sales, and business management. Beyond his role at KJM, Mark is a keen blogger, writer, and traveller, often sharing insights on the latest innovations in the home improvement industry.

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Timber - PVC - Aluminium - Windows, Doors & Conservatories in Hampshire

Battling the Traffic Drone: A Local’s Guide to Silencing the A303, A34 & M3

Battling the Traffic Drone: A Local’s Guide to Silencing the A303, A34 & M3

1. The Science of Silence: Understanding Decibels