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Norsound’s NOR400 acoustic letter plate comes acoustically tested up to 40dB whilst also being fire resistant up to 60 minutes and compliant with British Standard BS 476 Part 31.1 cold smoke leakage regulations.

The NOR400 has passed stringent durability measures. It is supported by the 'Secured By Design' UK Police flagship initiative and has been salt spray tested up to 480 hours, which follows the European standard BS EN 1670: Class 5. It is also PAS23 and 24 compliant, with a cycles test up to 30,000 cycles.

The NOR400 has been specifically designed to rectify the problem of unwanted sound being transferred in doors where cutting a hole in the centre of the door for a letter plate is a necessity. Previously this may have caused significant damage to the soundproofing of the door set but the NOR400 aims to protect its acoustic properties.

Available in Gold as well as satin and polished chrome, this high quality letter plate is the perfect solution for those wanting to not only secure a fire door but are also concerned with keeping unwanted sound to a minimum.

Screen colour may differ from actual product colour. All technical information is given as guidance only. Due to the technical nature of our products they are designed to be installed by a professional.

An acoustic, fire-rated letterbox? Is it really necessary?

After spending the time looking for, then specifying the right combination of seals to get the optimal decibel reduction and fire ratings for your door system, cutting a hole to fit a standard letterbox would seriously compromise the acoustic and fire-rated properties.

To remedy this, the NOR400 is cleverly designed to provide an effective smoke and acoustic seal, whilst the included intumescent liner maintains the integrity and rating of a 60 minute fire-rated door.

Do I need anything else with this product to fit it?
An intumescent mastic is a necessity in fitting this product. A tube of either the NOR115 Acoustic fire rated mastic or the Fire Wizard intumescent mastic would be suitable and can also be bought from us.
What aperture size shall I cut to house this product in the door?
We recommend against cutting out a hole in your door until receiving the Norseal Advantage letter plate. This is because the liner surrounding the product will cause the raw dimensions of the letter plate’s centre part to be inaccurate, and often there won’t be an exact figure for the size including liner.
Size Colour Code
12" Gold TBC
12" Satin chrome TBC
12" Polished chrome TBC