# Acoustic Wall Panels — Absorption Classes and Use

> Acoustic wall panels absorb sound energy rather than reflecting it, reducing reverberation and improving speech clarity within a room. They are rated by absorption class or NRC, and they do not insulate: they make a room sound clearer but do not stop sound passing through to the next room.

## What it is

Panels designed to **absorb sound energy** rather than reflect it, reducing
reverberation and improving speech clarity within a room.

| Type | Construction | Typical use |
| --- | --- | --- |
| Fabric wrapped | Mineral or PET core, fabric face | Meeting rooms, offices |
| Perforated wood | MDF or veneer, perforated, fleece backed | Boardrooms, auditoria |
| PET felt | Recycled polyester, moulded | Open plan, screens, baffles |
| Baffles and rafts | Suspended vertical or horizontal | High ceilings, open plan |
| Micro-perforated metal | Metal with fine perforation | Corridors, durable areas |

## Specification at a glance

| Property | Typical specification |
| --- | --- |
| Absorption | αw class A to E per EN ISO 11654, or NRC |
| Thickness | 25mm — 50mm typical |
| Mounting | Direct fixed, or on battens with an air gap |
| Core | Mineral wool, glass wool, or PET |
| Fire class | Named EN 13501-1 class |
| Facing | Fabric, veneer, perforated sheet |

## Specifying it properly

State the **absorption class or NRC**, the **mounting condition** including any
air gap, the **fire class**, and the **area and placement**. A panel's published
absorption figure assumes a particular mounting; quoting the figure without the
mounting is how a specified class A build-up becomes a class C installation.

## Where projects go wrong

- **Panels expected to give privacy.** They do not insulate.
- **Mounted flat to the wall** when the rating assumed a cavity.
- **Fire class ignored** in escape routes and high-occupancy rooms.
- **Placed decoratively** rather than at reflection points.
- **Fabric chosen for appearance** without checking it is acoustically
  transparent — a dense fabric over an absorber blocks it.

## Standards referenced

Sound absorption rating under **EN ISO 11654** and **ASTM C423**.
Reaction-to-fire classification to **EN 13501-1**.

## Frequently asked questions

### What is the difference between absorption and insulation?

Absorption reduces reverberation inside a room by soaking up sound energy; insulation stops sound passing between rooms. Acoustic panels do the first, not the second. Adding panels to a meeting room makes it sound clearer and less echoey, but it does nothing to stop conversation being heard next door — that needs partition mass, sealing and careful treatment of the ceiling void.

### How much wall area needs to be treated?

It depends on the room volume, the surfaces already present and the target reverberation time, but as a working rule 15 to 30 percent of wall area with a high absorption class transforms a hard-surfaced meeting room. Placement matters as much as quantity: panels on first-reflection points and on opposing parallel walls kill flutter echo far more efficiently than the same area spread evenly.

### Why does the air gap behind a panel matter?

Because absorption at low frequencies depends on panel depth plus the cavity behind it. A 25mm panel mounted tight to the wall absorbs speech frequencies reasonably but does little lower down. The same panel mounted on battens with a 50mm air gap absorbs substantially more at lower frequencies, which is where room boom and HVAC rumble sit. The mounting condition should be specified alongside the panel.

## Sources

- [EN ISO 11654](https://www.iso.org/standards.html) — Sound absorbers — rating of sound absorption
- [ASTM C423](https://www.astm.org/products-services/standards-and-publications.html) — Sound absorption and sound absorption coefficients
- [EN 13501-1](https://standards.cencenelec.eu/ords/f?p=CEN:105) — Reaction to fire classification

---

Source: https://hagerstone.com/materials/acoustic-wall-panel