A Guide To Steel Acoustic Doors

What is an acoustic door?

Acoustic doors are primarily used to aid in the soundproofing of rooms in order to keep external noise out or internal noise in. Their unique internals reduce amplitude and lower the transmission of sound by absorbing soundwaves. Generally speaking, an acoustic door forms just one aspect in part of a bigger plan to soundproof a whole building or room.

Acoustic values explained

Acoustic values are logarithmic; the difference between a 20db & 40db rated door isn’t simply “twice as much”. Each 10dB increment roughly increases the intensity by 10x and sounds twice as loud. Therefore, a 10dB improvement of your door rating means that you will hear roughly 50% less sound. A 20dB improvement will give another 50% of 50% on top = 75% less sound. As the decibel value gets higher, it becomes increasingly more difficult to soundproof against.

TOP TIP: don’t specify a 50dB door because you require it to be ‘really soundproof’. In many circumstances its overkill and you will pay a huge amount for it. 35-45dB is usually adequate for most acoustic setups.

How are steel acoustic doors tested and certified?

UK requirements for measuring sound intrusion are very specific. Doors are tested independently at a UKAS accredited laboratory to BS EN ISO 140-3 or equivalent.

On testing, with the door installed in an acoustic wall, sounds of all frequencies are played on one side with a microphone on the other. Typical sounds like road noise and traffic play to replicate real world conditions. The results are all collated to produce a dB value.

What is the purpose of your acoustic door?

Acoustic doors are used for many purposes within many different sectors. From recording studios and cinema rooms to plant rooms and engine rooms. The purpose of the door will determine the specification. If you’re installing the door on a home studio or converted shed, the likelihood is that a standard acoustic door will suffice. For larger industrial and commercial premises, other regulations may need to be complied with.

What specification do you require?

First of all, what Decibel or ‘dB’ rating do you need? It is unlikely you will achieve absolute silence from one side of the door to the other, so consider more-so the sound reduction you’d like to achieve. To put things into perspective, here is a chart of dB ratings and comparable sounds:

Decibel Example
25-30dB Loud talking is audible
30-35dB Loud talking is audible but difficult to distinguish
35-40dB Loud talking is faintly audible but cannot be distinguished
40-45dB Shouting is audible but cannot be distinguished
45-50dB Shouting is barely audible
50-55dB Shouting is not audible

Approved Document E – resistance to the passage of sound, quotes:

”Corridor walls and doors – 2.26. Ensure that any door has a good perimeter sealing (including the threshold where practical) and a minimum mass per unit area of 25kg/m2 or a minimum sound reduction index of 29db Rw”

Source: https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/468870/ADE_LOCKED.pdf

The spec of your door may need to comply with other regulations as well as its acoustic ability. Ask your architect or building control to advise you:

  • Is there a legal requirement for a certain dB rating?
  • Does the door also need to be fire rated?
  • Is the door a fire escape and will it need a push bar?
  • Does the door need to be of high security?
How much does an acoustic door cost?

From £150 stock doors, to bespoke acoustic doors costing upwards of £3,000, it all depends on the specification of door. This cost can fluctuate as a result of the following:

  • Acoustic rating – The higher the dB, the higher the cost. To improve the acoustic values, more and more varied materials are put inside the door leaf and frame. This increases the cost of materials and labour when in manufacture.
  • Fire rating – Fire rated doors cost more than non-rated doors, since the materials used must be fireproof. Not to mention the extra costs for R&D and testing, expect for this to almost double the cost of your acoustic door.
  • Door hardware – If the door is a fire escape, the price will be more than if it were a personnel door. Other hardware like door closers and d-handles will also increase the price.
  • Security level – The higher the level of security, the higher the cost of the door. Most acoustic doors hide something of high value behind them. The value of the goods should determine the security level of the door. Sometimes insurers specify certified security doors; speak with your insurer for advice.
  • Door size – The bigger the door, the bigger the cost. A double door costs more than a single door, too.
  • Finish – If you choose a special finish, like wood veneer for example, expect to pay a premium. Most steel doors are powder coated as standard.
An economical acoustic door

Most steel doors are manufactured with a honey-comb filling which offers no real acoustic value by itself. Just the general makeup of the steel door and frame with standard seals can achieve a value of 20-30dB.

Take our budget steel door, from just £189.99+VAT for instance

Rockwool insulated doors and frames can usually achieve 33-38dB. That is depending on the thickness of the door leaf and frame. The thicker the door, the more space to house insulation.

See our high security steel acoustic doors (38dB), from £349.99+VAT

For doors rated over 39dB, a more specialist combination of materials is used and will require a custom made door.

Spec your bespoke door here

DIY Acoustic Door Tips

Here are some cost effective ways to create your own acoustic door:

  • Install 2 cheaper doors back to back, with an air gap between. The doors must open away from each other. Therefore, ensure you have clear space to open the first door outwards and the second door inwards. There is no data to calculate what the dB will be if you fit 2 x 25dB doors back to back, but it will be a significant improvement. Hardwood doors are preferable over hollow doors.
  • Apply dense sound deadening material to the inside of the door and frame. Dense vinyl or MDF is particularly effective.

*A quick note at this stage*

Some suggest adding sound proofing foam to your door to help soundproof it. This does not work. This will only reduce echo within the room, it won’t stop sound from getting through the door.

  • Adjust your door so that it closes as tightly into the frame as possible. Any gaps are spaces for sound waves to get through.
  • Add self-adhesive seals between the door and frame to make considerable acoustic improvements. A brush seal or drop-seal at the bottom will help create a seal between the bottom of the door and the floor, too.
  • Add expanding foam into the frame cavities and apply silicone sealant over all gaps. This will reduce the sound waves travelling around the door frame and through cavities.
  • Drape a thick, multi-layered curtain over the door. Simple but extremely effective and underestimated.

Featured image “Small Bedroom Recording Studio”, by Dejan Krsmanovic, licensed under CC BY 2.0

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