Interior · SERVICE · REV 2026-10-06
Wall cladding
The face of the wall is not its behaviour. Solid wood of enough mass reflects in the speech range. The same wood, perforated, with an absorber and a cavity, absorbs in a band set by hole diameter, open area, and depth. Without those three the hole is ornament. Thin PET felt on a hard wall is weak at low frequency.
Definition
Cladding is a visible layer on a support. Acoustics ask whether the face is open to air, how thick it is, and what is behind it. The coefficient α comes from ISO 354 for a named mounting, with its frequencies. An open-area percentage on a drawing with no diameter and no cavity is not a specification. This page publishes no coefficient for any product and none for PET felt. At 100 Hz the wavelength is about 3.4 m, so a thin layer hard against the wall is not a bass tool.
Fire is the report of the assembly: face, adhesive, core, and substrate. A handsome veneer on an untested core inherits no class. The lower wall in an aisle is hit by a trolley and a chair. The impact layer may be acoustically harder than the upper wall, and the difference is calculated instead of assuming the whole wall absorbs. This page gives neither a fire class nor an impact joule.
When is this service needed?
Before the face is approved
The cavity and the absorber can still be drawn. The picture alone is late.
A rear wall that echoes
Cladding there is absorbent or tilted. On the side it may stay reflective to support speech.
An aisle that gets hit
The lower wall is a layer that takes impact. The fragile acoustic face sits above hand height.
A fabric substitution
It seals the pores or changes the fire behaviour. The report is tied again.
Where it is used
Hall walls
Side, rear, and a low ceiling. The acoustic role differs in each place.
Public corridors
Impact, cleaning, and exit fire. Absorption is secondary if it conflicts with those.
Rear theatre walls
A late echo. Perforation without an absorber is not enough.
Short-life exhibition walls
A visual skin may be enough. Do not call it acoustic without a build-up.
Parts of the solution
The face
Wood, perforated metal, fabric, or PET. Open area and diameter if there is a hole.
The cavity
A spacing off the hard surface. Changing it changes the band. It is written in millimetres on the detail, not here as a product figure.
The inner absorber
Fibre or felt at the tested thickness. Its absence makes the hole a texture.
Support and fixing
A frame that does not close the cavity and does not form a hard bridge over the absorber.
The impact layer
At the bottom of the aisle, denser, to a height above the line a trolley hits.
Engineering considerations
The hole is not absorption
Without a cavity and an absorber, energy returns from the hard back.
Low frequency
It needs thickness or spacing. Thin PET on the wall does not treat 100 Hz because the wave is long.
Distribution
A fully absorbent wall can kill a useful early reflection. Position comes from the section.
Fire for the assembly
Face, adhesive, and core. This page has no class.
Impact
The lower zone is separated on the detail. Assuming the same face from floor to ceiling breaks the bottom and changes the sound.
Materials
PET
A common porous felt. α comes from the report of its thickness and mounting. The name is not enough.
Wood
Solid and reflective, or perforated on condition of a cavity. A heavy varnish can seal the pores.
Fabric
Open or closed. A closed weave kills the absorber behind it. The tested one is the one installed.
Related systems
Treatment and RT60
Cladding is one way to change A. Coverage is not the time.
Isolation
Internal cladding does not close flanking. Do not mix the two pages.
Lighting
A spotlight punches the cavity or closes it. Its place is coordinated.
Furniture
A cupboard in front of the absorber removes it from the calculation. The free face is the area.
Design sequence
- 01
Decide the position: early support, killing an echo, or protecting an aisle.
- 02
If it is absorbent, write open area, diameter, cavity, and absorber, then ask ISO 354 for that.
- 03
Separate the lower impact metre from the upper face.
- 04
Tie fire to the report of the full assembly.
- 05
Do not turn an open-area percentage on the plan into an RT60.
Delivery sequence
- 01
The cavity is kept as drawn. Felt stuck flat is another build-up.
- 02
The tested face is installed, not a fabric that is “close”.
- 03
The impact layer is finished at its height. It is not replaced by an extension of the fragile face to save an item.
- 04
The fixing does not compress the absorber until it becomes solid.
- 05
The build-up is photographed before the face is closed, so it can be checked against the report.
Testing
Build-up match
Cavity, absorber, and face as in the report. A difference cancels the transfer of α.
Impact
The lower sample is inspected visually after early use. This page gives no impact energy.
No on-site α as a certificate
Inferring the coefficient from one room is an estimate. The certificate remains ISO 354.
Commissioning
A handed-over detail
Open area, depth, and material. Without them the wall is decor.
Fire and absorption reports
For the installed assembly only. This page adds no figure.
A free zone
What furniture covers is deducted from the acoustic area in the final calculation.
Maintenance
Painting the holes
It fills the opening and kills the role. Forbidden unless the design is redone.
Replacing PET or fabric
The same thickness and openness, or a new report.
Aisle impacts
Repair the lower layer before the face tears and exposes an untested core.
Common mistakes
Perforation with no absorber
A texture. Energy returns from the back.
PET as bass treatment
A thin layer is not enough against the wavelength at 100 Hz. No coefficient on this page proves otherwise.
A class from a picture of the veneer
Fire belongs to the assembly. The picture has no report.
An absorbent wall where a reflector is needed
Speech goes dry. Position matters more than covering every metre.
Short comparison
The comparison is a way to choose a path. It is not a product recommendation and it is not a code.
| Path | Fits when | Weakens when |
|---|---|---|
| A solid face | An early reflection is wanted and the mass is enough in the speech range. | When the rear face echoes. Solid cladding there makes the path worse. |
| Perforated with a cavity and absorber | Absorption in a band is wanted, and the build-up has a report. | With no cavity or no report. The hole is ornament and the coefficient is invented. |
| PET felt applied flat | Mid and high treatment with enough thickness, and a report for that thickness. | When the need is bass. A thin layer on the wall does not approach a quarter wavelength. |
Discussion ranges
Any number here is a preliminary discussion range from practice or a named reference. Replace it with the project criterion, laboratory data, and on-site measurement.
| Item | What is discussed | Limit of this page |
|---|---|---|
| Open area | Hole area over face area, with hole diameter and panel thickness. | It is not an α. Without a cavity, an absorber, and an ISO 354 report it does not enter an RT60 calculation. |
| The cavity | The spacing off the hard surface that changes the absorption band. | No product millimetre on this page. The figure is on the built detail, to the report, not to a guess. |
| The 100 Hz wave | About 3.4 m at 343 m/s. A picture of why a thin layer is weak at low frequency. | It is not an absorption coefficient. Temperature changes the speed slightly. ISO 354 for the mounting is the evidence. |
| Fire class and impact | From the assembly report and from the lower-layer specification if one exists. | No class and no joule on this page. A picture of the veneer does not carry them. |
What this page does not claim
No fire classification, absorption coefficient, sound pressure level, or legal capacity on this page may be copied into a quotation. Those values come from a product test report, a measurement, or the local code adopted for the project.
Questions designers and owners ask
Why does the perforated wall not absorb?
Because behind it is hard, or there is no absorber in the cavity. The hole alone is a texture. The report names the build-up that absorbs.
Does PET treat bass?
Thin felt hard against the wall does not. Low frequency needs thickness or spacing. The coefficient comes from ISO 354, not from the name.
Where do I take the fire class?
From the report of face, adhesive, and core together. This page does not give it.
Why is the bottom of the wall different?
Because it is hit. A harder layer protects it and may reflect more. Do not assume the whole wall absorbs.
Does cladding isolate the neighbour?
No. That is isolation and paths. Cladding is inside the room.
Technical sources
- ISO 354
Absorption of the named mounting. This page carries no coefficient.
- The assembly reaction-to-fire report
The class for face and core together. This page has no certificate.
- ISO 3382-1 after installation
The wall’s effect on the room. Open area is not that measurement.
Last editorial review: 2026-10-06. Review means the text was checked, not that a project was measured.
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A study starts from room volume, use, and existing condition, not from a product name. Fill the brief and copy it.
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