Acoustic sound panels: how they cut echo and what the ratings mean

What acoustic panels do and do not do

Acoustic sound panels are made to absorb part of the sound that reaches them instead of reflecting it back into the room. Danish maker WoodUpp, for example, sells its panels to calm echo in living rooms, offices, kitchens and home cinemas.

Absorbing sound inside a room is a different job from stopping it reaching the next room. The product page of Rockfon Sonar dB 43, a stone wool ceiling tile, shows the two as separate figures: a sound absorption rating of αw 0.90 for the room itself, and a room-to-room sound attenuation of 43 dB measured to a different standard, ISO 10848-2. So a panel chosen for its absorption figure says nothing about how much noise it keeps out of a room.

Types of acoustic sound panels

Types of acoustic sound panels

Type	What it is made of	Example from a maker’s listing
Mineral or stone wool panels and tiles	stone wool	Rockfon Sonar dB 43: 40 mm stone wool, fire class A1 under EN 13501-1
Acoustic foam	polyurethane or melamine resin foam	foam and Basotect tiles in the Addictive Sound range
Wood slat panels	veneer or wood-look slats fixed on black or grey felt	WoodUpp Akupanel, 240 × 60 cm, which the maker sells as a class A system
Felt panels	pressed felt boards	felt acoustic panels in the Addictive Sound range
Bass traps and diffusers	various	sold as separate product groups by Addictive Sound

Sources: Rockfon product page; Addictive Sound acoustic panels, which also states that the mineral wool it uses carries an A1 fire certificate; WoodUpp acoustic panels.

Reading the ratings: αw, class and NRC

Sound absorption is measured in a test room under ISO 354 and reported as a coefficient for each frequency band. Two single-number ratings are then worked out from those values:

• αw and class. EN ISO 11654 turns the measured curve into one value, αw, and sorts absorbers into classes A to E, as Ecophon’s guide to sound absorption classes explains. Class A absorbs the most.
• NRC. The noise reduction coefficient under ASTM C423 is the average of the absorption coefficients at 250, 500, 1000 and 2000 Hz, rounded to the nearest 0.05. That definition is spelled out in a laboratory test report by Peutz for Rockfon.

The two do not always move together. Rockfon lists its Sonar dB 43 at αw 0.90 and NRC 0.85, so when comparing two panels, compare like with like: αw with αw, NRC with NRC.

Why the mounting changes the numbers

An absorption figure belongs to a panel mounted in a particular way, not to the material alone. The Peutz report says so directly: the absorption coefficient is not a property of the material, and it depends on the size of the panel, how it is mounted and where it sits in the room. Its own test hung the panels 200 mm above the floor of the test room.

Ecophon makes the same point from the buyer’s side: absorption values given without the overall depth of mounting cannot be used for comparison. Rockfon’s Sonar dB 43 figures, for instance, apply to a suspension height of 200 mm. A panel glued flat to a wall may not reach the figures printed for the same panel with an air gap behind it.

What to check before you buy acoustic panels

1. The class or αw, with the mounting depth. “Class A” means little unless the sheet says how the panel was mounted for the test.
2. The test standard and laboratory. ISO 354 for the measurement, ISO 11654 for αw and class, ASTM C423 for NRC.
3. Fire classification. Stone wool products such as the Rockfon tile above are given as A1 under EN 13501-1; foam and felt products should state their own class.
4. Size and fixing. Panel format and whether it is screwed, glued or hung affect both the look and the result.

Kitovu does not sell acoustic panels. Decorative PVC and other wall boards, which are a different product, are covered under wall panels, and carpet tiles with a cushioned acoustic backing under carpet tiles.