acoustic curtain Certified: 3 Ways to Tell If a Lab Report Is Genuine

The term "soundproof" appears on thousands of curtains sold online. However, there are no regulations governing its use: any seller can apply it to any fabric, even a sheer curtain weighing 150 g/m². This guide explains how to distinguish, through three simple checks, between a " acoustic curtain " with truly measured performance and a mere marketing claim.

What You'll Learn

Why the law of mass is the first filter to apply
The 3 Essential Pieces of Evidence to Check Before Making a Purchase
How to Interpret an Rw Index Without Being Misled by the Maximum Value
The 5 Questions You Should Always Ask a Salesperson

Why the term "phonic" doesn't guarantee anything

Unlike fire-safety certifications (M1 classification, Euroclass) or thermal performance labels (EN 14501), the term “soundproof” is not governed by any mandatory labeling standards in France. A seller can use it freely, without ever having subjected their product to any laboratory testing.

This regulatory loophole is widely exploited in e-commerce: product descriptions claimto “reduce unwanted noise by up to 30 dB” without citing any source, report number, or standard. Under French law, such a claim constitutes a deceptive commercial practice (Article L121-1 of the Consumer Code) if it cannot be substantiated.

The Law of Mass: The First Physical Filter

Even before opening a laboratory report, one principle of acoustics stands out: the law of mass. The heavier a material is per square meter, the more it attenuates sound transmission. This relationship is linear and inescapable.

A curtain weighing 0.3 to 0.5 kg/m² (the typical weight of so-called “blackout” curtains sold in big-box stores) physically cannot provide the same light reduction as a fabric composite weighing 1.35 kg/m². It’s not a matter of brand or secret technology—it’s physics.

💡 A habit to adopt

Before checking anything else, ask for the weight per square meter of the finished product. If the seller cannot provide a specific figure, that is a red flag in itself.

"Reduces noise" vs. "Rw measured in the lab": the key distinction

Certified acoustic performance is defined in a specific way:

  Rw(C;Ctr) = 14(−1;−3) dB

  Maximum attenuation: 28.2 dB at 5,000 Hz

  Standard: NBN EN ISO 10140-2:2010

  Laboratory: Daidalos Peutz — BELAC ISO/IEC 17025 Accreditation

  Report No. A-2020LAB-060-I766-44092_E

The 3 pieces of proof you should request before making any purchase

The accredited report number

An acoustic laboratory report bears a unique number, assigned upon completion of the tests. This number must be provided upon request. The report must be issued by a laboratory accredited to ISO/IEC 17025 —in Belgium: BELAC; in France: COFRAC.

Red flag: "internal tests," "proprietary certifications" — none of these can replace third-party accreditation.

The applicable test standard

NBN EN ISO 10140-2: Sound attenuation (sound passing through the curtain) — effective against outdoor noise.
ISO 354: Sound absorption (reduction of indoor echoes) — two different requirements.

Warning: Absorption and insulation are used interchangeably without distinction, or the standard is not cited.

The Rw/maximum frequency value ratio

The Rw index is an overall value (125 Hz to 3,150 Hz). The maximum value corresponds to the frequency at which the curtain performs best—often between 3,000 and 5,000 Hz. It is misleading to present them as identical.

Example: Rw 14 dB (certified overall) + maximum 28.2 dB at 5,000 Hz. These two values do not describe the same thing.

Warning: a single "X dB" value with no frequency or Rw/max distinction.

What does a real lab report look like?

Parameter	Certified Value
Report Number	A-2020LAB-060-I766-44092_E
Laboratory	Daidalos Peutz — BELAC ISO/IEC 17025 Accreditation
Standard Applied	NBN EN ISO 10140-2:2010
Overall Rw Index	Rw(C;Ctr) = 14(−1;−3) dB
Maximum attenuation	28.2 dB at 5,000 Hz
Weight of the complex	1.35 kg/m²

5 Questions to Ask Any Salesperson

Question	Serious response	Warning Signal
Weight per square meter of the finished product?	Value expressed in kg/m²	"Heavy fabric" with no number
Which laboratory conducted the testing?	Name + BELAC/COFRAC Accreditation	"Internal Tests"
Test report number?	Number available upon request	No number
Which standard is applied?	ISO 10140-2 or ISO 354	No standards cited
Is Rw different from the maximum value?	Global Rw + max with frequency	A single value of "X dB"

Frequently Asked Questions

Does a " soundproof curtain " really reduce noise without any construction work?

Yes, within certain physical limits. It reduces sound traveling through a window or a lightweight partition. An ideal, reversible solution for renters. It is most effective against traffic noise (midrange and high frequencies), but less so for deep low frequencies.

How can you read an Rw index correctly?

The Rw value summarizes measurements from 125 Hz to 3,150 Hz. Rw(C;Ctr) = 14(−1;−3) dB means: 14 dB overall, 13 dB for music, and 11 dB for urban traffic.

Sound Absorption vs. Sound Attenuation: What's the Difference?

Absorption reduces internal echoes (ISO 354). Attenuation reduces the sound that passes through a wall (ISO 10140-2). Two distinct measurements for two different purposes.

Why do some curtains claim to be "30 dB" without any evidence?

There is no rule requiring prior verification before displaying a figure online. However, Article L121-1 of the Consumer Code requires that any performance figure displayed be verifiable upon request. Without an accredited report, such verification is impossible.

Laboratory Evidence