The National Company With A Local Reputation - 1st Secondary Glazing!

Residential Installation or Supplied to your doorstep - Commercial Installation, Trade & Specifiers

Home     Products & Services     Technical & Test     Information     Gallery     Other     Contact     Site Map
London Art Gallery - Internal Secondary Glazing for Noise with Gothic Arched Heads

Sound & Noise Reduction

Please - Bear With Us - this Section is necessarily lengthy - Good Noise Insulation is a complicated subject - even for us!

If you would prefer to have a chat with someone, feel free to give us a call.

For Quick Navigation of this section

We live in an increasingly Noisy Society.

Not only in the Major Cities, but across the Country in Towns & Villages everywhere - Intrusive, Irritating, Stressful and Sleep Disturbing - Noise is coming at us from All Directions.

Road Noise from Cars & Motorbikes, Buses, Lorries & Taxis - Railway Station & Train Noise - Aircraft & Airport Noise - Pubs, Clubs & Discos - Ambulance, Police & Fire Engine Sirens - People Shouting & Talking Loudly in the streets at All Hours - Car & Burglar Alarms - Dogs Barking - Noisy Neighbours.

The List is Endless & Seems to be Growing Longer by The Day.

For many people, a Good Nights' Sleep is a Thing of The Past & the Simple Pleasure of a Quiet Evening At Home no Longer Exists.

Why Secondary Glazing?

The Majority of Intrusive Noise enters a building through its' Most Vulnerable Point - the Windows & Doors.

Effective Noise Insulation is achieved by creating an Additional Barrier - a Second Layer of Glass.

However, Noise is not So Easily Defeated!

Other Factors play a Significant Part in Effectively Eliminating or Reducing Noise To a Tolerable Level:

  • The Cavity between the Two Layers of Glass
  • Correct Specification of the Glass Type
  • Framing
Waldorf Chambers, London - Bespoke Internal Secondary Glazing for Noise

Secondary Glazing, despite what your friendly neighbourhood Double Glazing Representative may tell you, is by far & away the Most Effective Solution for Combating Noise, for the following reasons:

  • The gap between the two layers of glass when installing Secondary Glazing inside the Existing Window is always greater than when fitting Sealed Unit Replacement Double Glazing - and the gap plays a crucial part in effective Noise Reduction - for 4mm Glass each increase in the gap of 25mm (1 inch) approximates to an increase in Noise Insulation of 0.75dB Rw - for 6mm Glass each increase in the gap of 25mm (1 inch) approximates to an increase in Noise Insulation of 1.25dB Rw (See explanation in the next section for dB Rw)

  • It is important to Correctly Specify the Glass - in general, the thicker the better - but it is also relevant, dependant upon the Type and Frequency of the Noise, to use Different Thicknesses of Glass for the two layers of glazing in order to tackle Acoustic Resonance which results in Vibration - nobody wants to cut out the Noise of a Passing Lorry only to have to Listen to the Glass Vibrating! Laminating either one of the Glass Layers further reduces Sound Transmission.

  • Both the Glass & the Framing are Helping to Control the Noise - if a Solid Timber Framed Window is removed & Replaced with a Hollow Framed PVC-U Replacement Window, the New Frame will be a Less Effective Barrier - so you end up Gaining a Bit by having the Sealed Unit and Losing a Bit because of the Less Effective Frame.

  • Government (or other similar work such as Airport Sound Insulation Schemes) Funded Noise Insulation work around New Roads, etc, is always Secondary Glazing, never Replacement Windows.

  • A large proportion of our work involves fitting Secondary Glazing inside Replacement Sealed Unit Double Glazing.

^ Top of Page

The Facts & Figures - An Explanation of Noise & Its' Measurement - With Sources & Links

  • What is noise? Noise is 'sound which is undesired by the recipient'. In other words noise can be any sound that intrudes or disturbs or annoys.

  • How is it measured? - Sound levels are measured in decibels (dB) However, the human ear is not equally sensitive to all frequencies or types of sound.

  • A-Weighting [dB(A)] - An electronic filter that approximates the frequency response of the human ear. A-weighting is used to measure average noise levels. A-weighting is usually referred to simply as dB.

  • Rw Weighted Sound Reduction Index - R-values are measured in tests of octave or 1/3rd octave bands. The resultant curve is adjusted so that any shortfall of the actual measurements below the standard curve, averaged over all the octave or 1/3 octave bands, is not greater than 2dB. The resultant value of the curve at 500Hz is the Rw. General Sound Reduction is expressed as dB Rw General Rated Reduction [Rw].

  • dB Rt - Measurement used for the Interior Noise Levels coming from Outside Typical Road Traffic Noise in City & Town Centres. Rtra (Reduction of road traffic noise) is expressed as dB Rt. This is an Index used for measuring a windows' specific performance in Reducing Road Traffic Noise from Outside.

  • The three-decibel rule The decibel is a logarithmic measurement; sound intensity doubles with every 3 dB increase. Thus sounds at 88 dB are actually twice as intense as they are at 85 dB and 115 dB is 1000 times as intense as 85 dB. Conversely, a 3 dB decrease in sound intensity represents a halving of the noise.

  • An average single glazed window - Achieves around a 25 dB Rw Noise Reduction over & above just having a hole in the wall!

  • dB Rw & dB Rt - Are always expressed as the Combined Noise Reduction of the Glazing System - so a typical single glazed Primary Window + standard Secondary Glazing = a Combined Noise Reduction of 37 dB Rw.

  • A comfortable (inside) sound level is around 35dB in daytime and 30dB at night.

Balanced Tilt In Vertical Sliders over Georgian Sash Windows - London for Noise

Information from

^ Top of Page

The Solution

We have been dealing with both Residential & Commercial Noise Reduction for many years & it is the fastest increasing sector of our business.

Standard Secondary Glazing primarily designed for Thermal Insulation will as standard give Excellent Noise Insulation.

To put this into perspective,

  • A 1st Secondary Glazing Unit with 4mm Low E Glass and 85mm cavity inside a putty glazed timber window with a single pane of 4mm Float Glass achieves a 37 dB Rw General weighted reduction & a 31 dB Rt Traffic Noise Reduction.

  • A 1st Secondary Glazing Unit with 6mm Float Glass, a 150mm cavity and fitted inside a 4mm single glazed primary window achieves a 45 dB Rw General weighted reduction.

^ Top of Page

  • Things have now moved on even further since we started Importing Stadip Silence laminated glass from Saint-Gobain Glass in France.

    This Exceptional Glass has been developed Specifically for Noise Reduction.

    Using this glass we are able to achieve in the region of a 48 dB Rw Noise Reduction with a 150mm cavity & a 45 dB Rw Noise Reduction with a smaller, 75mm cavity.

    This means that we can now carry out Noise Reduction Installations that are both More Effective and much more Aesthetically Pleasing.


Vertical Slider over Arched Head Sash - London for Noise

^ Top of Page


  • When opening Primary & Secondary Windows for Ventilation ensure that you open them in the staggered position, i.e., if the Left Hand side of a Casement Window is opened, then open the Right Hand side of the Secondary Unit - this will improve Sound Reduction by 15 - 25 dB Rw depending upon the Noise Source/s, window size & exact configuration. (Pages 4 & 5)

^ Top of Page

Road, Rail & Aircraft/Airport Noise

Our Secondary Glazing Systems are effective for all types of noise. However, applications differ slightly & other factors also play a part:

  • Road & Rail Noise - It is important to use an Asymmetrical Glazing System, i.e., 1 pane of 4mm glass coupled with 1 pane of 6mm glass - this is effective in Reducing the Resonance & Vibration caused by the Lower Frequencies produced by Diesel Engines & Trains.

  • Aircraft & Airport Noise - The same Principles apply but dependant upon the Direction & Altitude that the Noise is coming from you should also consider Improving Your Loft Insulation.

^ Top of Page


People in 23 urban areas can now see a snapshot of noise levels in their neighbourhoods.
A new Defra (Department for Environment, Food & Rural Affairs) website launched today, provides maps showing the level of environmental noise from major industries, road and rail networks & airports in 23 urban areas in England. The information, covering 80,000 km of roads within urban areas, 28,000 km of major road networks, major airports and almost 5,000 km of railways, will be used to draw up action plans to reduce unreasonable levels of noise, where practical. In urban areas these will also include measures to protect designated quiet areas.
Users are able to search by postcode to access maps that show noise levels over an average 24 hour period, as well as during night time hours only. The site also includes information on the number of people exposed to these levels of noise. All member states have to produce maps under the EU Environmental Noise Directive.

^ Top of Page

Useful Links

^ Top of Page