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Understanding Acoustic Curtains - Sound Absorption & Sound Proofing Insulation

Understanding Sound Proof Curtains & Sound Absorbing Curtains



Before commencing this article, we are going to be looking at the difference between 2 elements and why buying products on the internet knowledge on a subject assists you in understanding which product is best for you. The 2 different areas when it comes to acoustic curtains. Absorption and the other is insulation (sound blocking).


Sound Absorption is used to reduce echoes and sound going around a space See part 1

Sound Proofing this is to stop sound from passing/entering into a space. See Part 2




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Most curtaining products out there in the market place are beneficial to sound absorption and will have very little impact on sound insulation. Direct Fabrics offers various linings that will offer increasing amounts of sound insulation and our face fabrics are excellent for absorption. The perfect combination

  1. Unlined Curtain - Absorption ONLY - "A" to "C" Grade.
  2. Duo Lined Fleece Interlined with face fabric - Upto 7 decibels in real world test
  3. Vinyl 610gms with Face Fabric - Upto 11 Decibels in a laboratory
  4. Vinyl 610gms & Duo Lining & Face Fabric - Over 10 Decibells. in real-world office.


Understanding Sound Volumes in Decibels "DB"

Changes in STC/Changes in Apparent Loudness:

Changes in STC RatingChanges in Apparent Loudness
+/- 1dbAlmost imperceptible
+/- 3dbJust perceptible
+/- 5dbClearly noticeable
+/- 10dbTwice (or half) as loud


Defining Sound Volume in Real Life

Sound Level DBSource Sensation
130Jet Aircraft at 100ftPhysical Pain
110Thunder / Artillery / DiscoDeafening
90Loud Street / Loud FactoryVery Loud
70Cocktail Party, Noisy Office, Average Street NoiseLoud
50General Office, Noisy HomeModerate
30Private Office, Quiet Home, Empty Gym,Faint
10Russle Of Leaves, WhisperVery Faint
0Threshold of AudibilityNil


Sound Absorption – Acoustic Curtains

When working with loud echoes in spaces it can be incredibly frustrating to stop sound reverberating around the room. This is where an acoustic curtain come in. Depending on the fabric it will have a varying effect on the amount of absorption that It takes and effects the sound passing back around the room.

To see how good a fabric or product is at absorbing sound in a room then you need to complete the

Sound absorption test EN ISO 354. This grades a product between A – E based on how absorbent a material is. When sound is projected into a room it will hit the surfaces and then it will either be transmitted through things like ceilings and walls or it will be reflected back into the room. So in a basic form the test is how much sound is sent out will return.

Example Imagine. 100 units of sound are sent into a room, 80 units are transmitted out of the room and then 20 are recorded back in to the space.

Thus the sound absorption coefficient is 0,8.


How is Sound Absorption Calculated

Α = converted Energy +  transmitted energy in relation to the incident.

The incident is the sound initially sent out.

The main aim of materials hung around rooms like recording studios and theatres is to stop the sound reflecting back around and ruining the transmission of the direct sound.

By having fabrics that are highly graded like black wool serge and expression dimout fabric you are limiting the amount reverberation back into the room. This is extremely important for recording studios and also quiet spaces like offices.

Imagine being in a large gymnasium with concrete blocks all the way around the room. If you shout you will get a large amount of echo

Here are some example reports for our best selling acoustic fabrics.


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Which Fabric is Best for Sound Absorption.

Overview Direct fabrics will continue to add to the testing list. Direct Fabrics will add additional fabrics as demand for fashion products increases. However, the expression product testing has a gorgeous herringbone running through the fabric and the team feel this is a perfect example of

Working with a variety of suppliers we have tested some fashion dimout products as well as wool serge materials.

The core product for theatres, exhibition centre and performance centres is black wool serge material. This is a chosen due to being cost-effective and performance grading of "A" / "B" depending on fullness.


Direct Fabrics is now recommending a designer fabric called Acoustic Herringbone which is dimout so 90+% light stopping even when unlined., It is also a "A" Rated acoustic fabric which means that you get the highest sound absorption and also a beautiful finish with a herringbone effect for a price lower than a coloured wool serge. See Lab test result below.

Prices at the time at writing this article may vary compared date when reading

FabricApplicationFullness (How Pleated)WeightSound ClassTestAWCurtainsFabric Only
Acoustic Dimout ***Dimout100%360gmsA100mm0.95CurtainsFabric
Coloured WoolStd Shade100%565gmsA100mm0.85
Standard Wool SergeStd Shade100%400gmsB100mm0.85Curtains
Standard Wool SergeStd Shade50%400gmsC100mm0.75Curtains
Coloured Wool BlackStd Shade50%565gmsB100mm0.8Fabric
Kilo Wool SergeStd Shade100%800gmsC100mm0.65


Deciding which fabric to purchase

Very simply you have a choice of a low cost black wool serge for a quick and effective drape to reduce the transmission of sound around a space at different frequencies. Or you can use a decorative product that is slightly more expensive that will give you even more than the standard wool.

Our Hemisphere Grade B Acoustic Rated and Acoustic Herringbone Grade A Rated are both excellent value and offer a designer finish.


Understanding Gradings and Frequency Results - Acoustic Absorption.

This fabric our acoustic herringbone is the best fabric we have present and is tested to "A" rating for absorption and a 0.95 absorption coefficient.


Sound Insulation Curtains - Sound Proofing Curtains

Introduction to Sound Proofing Curtains

  1. I am trying to block sound from entering my room.

To get this result you are looking for a sound blocking curtain. In the market, there are a lot of product that state they do this but in truth, they just don’t offer it in reality. Direct Fabrics has tested all of the vinyl products to EN ISO 10140-2 which is for sound insulation (sound proofing). This means that they have a lab backed report for there applications.

See our range of soundproofing curtains

Our entry-level product is sound tested to a result of 11 decibels in a lab environment. Obviously, in a practical application, this will not be sealed on all sides but you will still get a good reduction of between 5-8 decibels. Combining this with our fleece blackout fabric you will get close to 10 decibels in a working environment. See our videos.

To be clear, it is all dependent on what your trying to do.


Sound Proofing Curtains and Different Uses & Effect

  • In a new build the windows should be of a high standard and it should mean that the they are well constructed. So sound proof curtains will not stop the road noise coming through as they are deep sounds
  • Room partitions, our curtains are ideally suited to this. Our Curtains will block upto 10db with 3 layers and with further customisations can perform even better.
  • Drum Room Studio, stop the sound passing out of the room. By covering doorways and the walls you are reducing the sound passing around and as such out of the room. This will work well for stopping the sound.


Understanding Sound Proofing / Sound Insulation / Sound Blocking

It is a common misconception that having foam egg carton shapes on the wall will stop sound coming into a wall. This is simply incorrect. Imagine sound as water, if you made a wall of sponge do you think that it will stop the water passing through. No it wont. Then imagine an aquarium tank made of thick glass, sound will work in the same way as glass and it will stay within the tank. This is the same with sound passing between spaces.

From Direct Fabrics investigation and speaking with sound labs. We have discovered that the best product for reducing sound transmission is a product that acts as a rigid barrier between spaces and is strong and dense.

Using an MLV (Mass Loaded Vinyl) combined with an absorption fabric will give an excellent sound reducing curtain. However, it should be known that even having a super thick layer of MLV or similar fabric will still let sound pass through any air gaps. But you should get a 10 to 20db reduction depending on which MLV you like.

Please speak to the direct fabrics team for specialist products that will work for you windows for a complete sound solution.

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Do Sound Blocking Curtains Work?

This subject is particularly difficult to quantify, and all environments will differ.

A particularly good analogy I like to use when thinking about partitions and blocking sound is when you are driving in your car. You have the windows closed and it is quite quiet but as soon as you open the window even as much enough to slide an envelope through you can hear a large amount of sound. This is because sound is like a liquid and flows to wherever there is a gap. It will bounce off surfaces until it finds a route to go.

When deciding to look for a sound insulation fabric it all comes down to the mass of the product and that it is tightly woven and doesn’t allow anything to pass through it.


Option 1 - Our Best Selling Curtains - Face Absorption Fabric Blackout Fleece Lining

Please see the certificate confirming the 11db reduction for this curtain.

As above remember that this material also is a grade A sound Absorber.

Acoustic Test Result 2 Layer Curtain Insulation Test Result 11db Flat

Direct Fabrics now offer 2 product in our range a lightweight PVC Vinyl that is flame retardant and has been independently tested to EN ISO 140-2. Through this test, it has received a rating of 11DB reduction in sound transfer in a space. This combined with our duo lining interlined fleece and our acoustic face fabric has given a real-world result of 10 decibels in a real situation.


If you want to retrofit you acoustic lining straight to an existing curtain, then you can purchase this product


This curtain has also been tested with a double glazed window that shows an uplift of 4db above the performance of the window.

Our other vinyl insulators for soundproofing have been brought into the range to offer heavier weight products that increase the mass in-between spaces and so insulate further. By using these materials we can reduce the sound transference between spaces. The more mass and different compositions within a substance the better it will perform.

Our 900gms vinyl will perform between the pink and yellow lines. Giving around 13 decibels of reduction, this particular weight hasnt been tested but we can estimate the result.

Heavier options are available but the heavier you go the less maluable they are and more weight to go through the curtain tracks installed.

With Curtains ensure you use quality curtain tracks to get the best and most simple operation.

Metal Curtain Tracks




Do Sound Proof Curtains Work?

In a word YES!  Direct Fabrics believe in testing our products when being used in real-world test scenarios, not just in perfect lab conditions. For the best testing, we like to test our products in laboratories and also in real world setups. For some setups we have managed to set the up in laboratories for true proven results.

Real-World Testing of our Acoustic Curtain as a Room Divider

Testing the Curtains with Double Glazed Windows

Direct Fabrics is an industry leader in the field of sound proof curtains and believe in seeing if they actually work.  In our test we saw a 4db uplift over and above the window

Curtain on Track over Window Testing Lab With Window




Test Results

OVerlay Window and Curtain test

Option- Acoustic Membrane / Mass Loaded Vinyl MLV - MLM 5kg.





















Mass loaded vinyl is a heavyweight vinyl product that has a weight generally of between 5kg and 10kg and is ideally suited for stopping airborne sound. It has a greater weight than lead and will be perfectly suited to stop sound passing between spaces when fully enclosed between objects. It is usually used a floating wall barrier between stud work and pasteboard for cinema rooms, but Direct fabrics has been trialling this in panel form. As a barrier, it is shown to reduce sound transmission by 27 DB in accordance with ENISO717-1. See Image.

Direct Fabrics current offer a 5kg Acoustic Barrier Fabric that is available in a 120cm Width. We sell this manufactured into panels with eyelets above the panel. These are Sail eyelets and are 20mm. These are ideally hung onto wall screws or tieback hooks.

Mass Loaded Vinyl 5kg per metre square has been tested to 27 DB in a lab environment.

It is an ultra heavy weight product and can provide excellent sound results. As a loose cover, it will reduce sound by 10-20 decibels depending on installation and reduction of air gaps.

Negatives of Mass loaded Vinyl.

The product is a very industrial product and is made from a mineral rough compound vinyl. It is not decorative. Where it is great is for blocking sound but please note it is very heavy and difficult to put in situation. It is ideal to mount on to walls that not going to be moved.







Installation of your Products

  • Once you have chosen your product it is imperative to ensure that it is fitted wider than the space being blocked. This will allow for the sound not to pass round the edges of the installed barrier. So if using an mlv or vinyl use some double sided velcro or tape to attach the edges back to the wall.

If using curtains then also attach the curtain edges back to the wall.

  • Where possible have an overlap of the fabrics in the middle to get maximum coverage to stop passing through
  • Room dividers are best suited to be ceiling mounted to reduce the air gap over the top of the curtain.



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