Soundproof curtain: how to choose the right model

What is a soundproof curtain and how does it work?

A soundproof curtain is a multilayer technical curtain designed to absorb and block sound waves. It works on two complementary physical principles:

• Absorption through mass: the dense fabric absorbs part of the sound energy instead of letting it bounce back. The heavier the fabric, the more it absorbs. The acoustic mass law predicts a gain of about 6 dB each time the surface mass of the material is doubled.
• The air gap: the space between the window and the curtain (5 to 15 cm) creates a mass-spring-mass effect that dampens sound vibrations. It is the same principle as double glazing, applied to textile.

A "soundproof" curtain that relies only on the thickness of a single fabric cannot reach significant performance. It is the multilayer construction (decorative fabric + high-density wadding + acoustic membrane) that makes it possible to exceed 15 dB of attenuation. The reference standard for measuring acoustic insulation is NF EN ISO 10140.

The 5 criteria for choosing an effective soundproof curtain

Criterion 1: fabric density (the No. 1 factor)

The weight of the fabric is the first indicator of soundproofing performance. Here are the real thresholds:

• 150 to 300 g/m²: standard thick curtain. Attenuation: 5 to 7 dB (barely perceptible). Blocks light, not noise.
• 300 to 500 g/m²: mid-range soundproof curtain. Attenuation: 12 to 18 dB (clear improvement). The best-known models on the market (Moondream: 16 dB max) fall into this category.
• 500 g/m² and above: high-performance soundproof curtain. Attenuation: 18 to 25 dB (comparable to a closed interior door). This is the category Kurtens curtains belong to (620 g/m², 22 dB measured*).

Below 500 g/m², soundproofing remains limited. This threshold is not arbitrary: it corresponds to the point where the mass of the fabric becomes enough to significantly block vocal frequencies (300 to 3,000 Hz), which make up most urban noise.

Criterion 2: multilayer construction

A heavy single-layer fabric is not enough. Soundproofing performance comes from assembling layers with complementary functions:

• Outer layer (decorative fabric): absorbs the first sound reflections.
• Middle layer (high-density wadding): absorbs sound energy through friction in the fibres. This is the layer that does most of the work.
• Inner layer (technical membrane): blocks the residual waves and prevents direct transmission.

A 2-layer curtain reaches 12 to 18 dB. A curtain with 3 layers or more reaches 18 to 25 dB. The difference is significant: 6 dB more is noise perceived as half as loud.

Criterion 3: full coverage of the opening

A soundproof curtain that leaves 5 cm of space on the sides or 10 cm at the bottom loses 30 to 40% of its effectiveness. Sound, like air, slips through the slightest gap. A gap representing 1% of the surface lets through up to 50% of the sound energy.

This is why a made-to-measure soundproof curtain systematically outperforms a standard-size model by 3 to 5 dB. Exact dimensions eliminate side leaks. The curtain should extend 15 to 20 cm beyond each side of the window, the rod should be positioned at least 10 cm above the frame, and the bottom of the curtain should graze the floor (2 to 3 cm of clearance maximum).

Criterion 4: measured and disclosed performance

This is the most objective criterion and the one most sellers avoid. A soundproof curtain worthy of the name displays a measured attenuation in decibels, not just a "anti-noise" or "sound insulation" label on the product page.

The questions to ask:

• Is the figure in dB disclosed? If not, be wary.
• Does the test measure the installed curtain or just the fabric in a laboratory? A fabric can have a good absorption coefficient (sabine alpha) while still letting noise through the sides once it is hung.
• Is the figure a maximum on certain frequencies (high-pitched) or a weighted average? A curtain can attenuate 30 dB on high frequencies and only 12 dB on low frequencies.

At Kurtens, the stated attenuation is 22 dB measured under optimal test conditions*. A reproducible figure, not a theoretical maximum. To understand what decibels mean, read our article what 30 dB of attenuation really represents.

Criterion 5: complementary functions

A quality soundproof curtain does not only insulate against noise. The same properties (mass, density, multilayer) that block sound also block heat and light. The best models combine three performances in a single curtain:

• Sound attenuation: 18 to 25 dB
• Thermal insulation: 5 to 7°C of gain
• Blackout: 95 to 100%

The Kurtens made-to-measure soundproof curtains combine 22 dB of attenuation*, 100% blackout* and up to 7°C of thermal gain* in a 620 g/m² fabric. Buying three separate curtains costs more and works less well than a single multilayer curtain designed for all three functions.

Summary table: the 5 criteria to check

What a soundproof curtain can handle and what it cannot

A soundproof curtain is very effective against airborne noise that comes through windows and doors: traffic (70-80 dB), horns, passers-by's voices, street works. Windows are responsible for around 40% of a home's sound loss.

What it does not handle:

• Neighbour noise through party walls: the sound travels through the wall, not the window. The curtain can do nothing about it. Solution: heavy furniture against the shared wall (5 to 10 dB of gain).
• Impact noise (footsteps from above): it travels through the building structure. Solution: a thick rug with an acoustic underlay (10 to 20 dB on impacts).
• Very powerful low frequencies: nightclub music, heavy construction vibrations. These frequencies require much greater mass to be blocked.

For a complete guide on insulating an entire apartment without renovation work, read our article apartment soundproofing without renovation work: 5 solutions.

How to maximise the effectiveness of your soundproof curtain

The curtain alone only delivers its full potential if it is correctly sized and installed. Here are the 4 installation rules:

• Side overhang: 15 to 20 cm beyond the frame on each side of the window.
• Height: rod positioned at least 10 cm above the top of the window. The curtain should reach the floor (2-3 cm of clearance maximum).
• Glass-to-curtain distance: 5 to 10 cm between the glazing and the fabric. This space creates the mass-spring-mass effect that strengthens the insulation.
• Window seals: worn seals let noise through around the frame. Replacing the seals (5-15 euros, 30 minutes) adds 3 to 5 dB to the curtain's performance. The combined gain of curtain + new seals can reach 25 to 27 dB.

For dimensions, see the size guide. For choosing the rod (a 620 g/m² curtain needs a solid fixing), see the fixings guide.

*Data from tests carried out under optimal conditions.

Frequently asked questions