What an Acoustic Panel Actually Does
Acoustic wood slat panels are one of the easiest decorative products to sell and one of the easiest to mis-specify. Buyers often treat "acoustic" as a single property, when in fact a panel system absorbs a certain range of frequencies, reflects others, and can also be specified for sound insulation, which is a completely different performance.
The practical distinction:
- Absorption reduces reflected sound inside a room. It is measured by the noise reduction coefficient (NRC) and by the weighted absorption coefficient (Alpha W). This is what slat and felt panels do.
- Insulation reduces sound passing from one room to another. It is measured by Rw or STC, and it depends on the whole wall build-up, not on the decorative panel.
A slat panel will not stop noise from the room next door. Sold as absorption, it is an excellent product. Sold as insulation, it produces a complaint.
Understanding NRC
NRC is a single number averaged from absorption coefficients measured at 250, 500, 1,000 and 2,000 Hz, rounded to the nearest 0.05. It runs from 0 (perfectly reflective) to about 1.0 (fully absorptive at those frequencies).
| NRC | Classification | Typical build-up | Where it is appropriate |
|---|---|---|---|
| 0.35 to 0.50 | Low absorption | 12 mm slats, no felt, direct fixed to wall | Feature walls where appearance is the priority |
| 0.50 to 0.65 | Moderate | Slats on 9 mm PET felt, 20 mm cavity | Offices, meeting rooms, restaurants |
| 0.65 to 0.80 | Good | Slats on felt, 50 mm mineral wool behind | Conference rooms, classrooms, clinics |
| 0.80 to 0.95 | High | Slats on felt, 50 to 100 mm mineral wool, air gap | Studios, auditoria, open-plan call centres |
Two details matter more than the headline number. First, most slat panels absorb well above 500 Hz and less well below 250 Hz, so they control speech and treble but do little for bass. Second, NRC is measured in a laboratory reverberation room on a specific mounting; the same panel fixed directly to a plaster wall performs noticeably worse than the test suggests.
Always ask which mounting the report used: type A (direct fixed), type C (with an air cavity), or with additional insulation. The same panel can differ by 0.15 to 0.25 in NRC between mountings.
MDF Slats Versus Solid Wood Slats
| Factor | MDF slats | Solid wood slats |
|---|---|---|
| Core material | Medium density fiberboard, 1,200 to 1,500 mm sheets | Paulownia, pine, rubberwood or oak |
| Density | 700 to 850 kg/m3 | 350 to 700 kg/m3 depending on species |
| Weight per m2 | 4 to 8 kg | 3 to 7 kg |
| Dimensional stability | Good in dry interiors; swells with moisture | Good if kiln dried to 8 to 12 percent moisture content |
| Fire treatment | Can be treated to B1; verify report | Requires impregnation or coating; harder to certify |
| Acoustic performance | Similar in the mid and high frequencies | Similar; low-frequency behavior depends on cavity |
| Appearance | Consistent, wide finish range including veneer and laminate | Natural grain variation, premium feel |
| Price per m2 FOB | USD 12 to 28 | USD 20 to 45 |
| Best for | Commercial projects needing consistency and fire documentation | Premium hospitality and residential where grain matters |
For most export projects, MDF with a quality finish and a proper fire report is the pragmatic choice. Solid wood sells on appearance, not on acoustic advantage.
Felt Backing: The Part Buyers Underestimate
The backing material is doing much of the acoustic work and all of the safety work. Options:
- PET felt, 9 mm. The standard. Made from recycled bottles, typically 60 to 80 percent recycled content, density around 200 to 300 kg/m3. Provides moderate absorption and a clean edge.
- PET felt, 12 mm. Higher absorption, stiffer, better for wide slat spacing.
- Recycled cotton felt. Good absorption, but check fire performance and moisture behavior carefully.
- Mineral wool behind the panel. Adds the most absorption per dollar, especially below 500 Hz. Not part of the decorative panel but essential for a good NRC claim.
Ask for the felt's fire certificate separately. A panel that carries a B1 result for the slats and no documentation for the felt is an incomplete specification.
Slat Spacing and Geometry
Slat spacing changes both the look and the acoustics.
- 9 to 13 mm slats with 9 to 13 mm gaps is the classic 3D slat wall. Around 50 percent open area, good mid and high frequency absorption, and the strongest visual rhythm.
- Wider slats, 20 to 40 mm with 10 to 20 mm gaps look calmer and read better on very large walls, but achieve slightly lower absorption.
- Narrow slats at 6 to 9 mm with wide gaps maximize open area and absorption, and suit acoustic-critical rooms, but they look busier.
Open area is a useful proxy: 40 to 60 percent open area with felt behind is the sweet spot for speech-range absorption in offices and restaurants.
Installation
- Fix battens or a subframe at 400 to 600 mm centers. Direct fixing to a solid wall loses 0.10 to 0.20 NRC compared with a cavity mounting.
- Leave a cavity of 20 to 50 mm where absorption matters, and fill it with mineral wool for the best result.
- Orient the panels consistently. Vertical slats make rooms feel taller; horizontal slats make them feel wider. Do not mix directions on one elevation unless it is deliberate.
- Set out from the center so both edges are equal. Slat walls make an uneven edge gap very obvious.
- Cut with a fine blade and keep the felt clean; compressed or dirty felt looks bad at the joint.
- Detail the corners. Use matching corner profiles or a shadow gap; butt joints between two slat directions never look right.
Typical Projects and What They Specify
| Project type | Typical specification | Target NRC |
|---|---|---|
| Open-plan office | MDF slats 27 by 12 mm, PET felt 9 mm, 30 mm cavity | 0.60 to 0.70 |
| Conference room | MDF slats, felt 12 mm, 50 mm mineral wool | 0.75 to 0.85 |
| Restaurant | MDF or wood slats, felt 9 mm, cavity 20 to 30 mm | 0.55 to 0.70 |
| Hotel corridor | Decorative slat panel, felt backing, direct fix | 0.35 to 0.50 (appearance-led) |
| Classroom | MDF slats, felt, 50 mm mineral wool in cavity | 0.70 to 0.80 |
| Studio or auditorium | Engineered absorber build-up, slats as facing | 0.85 to 0.95 |
What to Put in the Specification
- Slat material, dimensions, spacing and open area percentage.
- Felt type, thickness, recycled content and fire certificate number.
- Cavity depth and whether mineral wool is included.
- Mounting type used in the acoustic test, with the report reference.
- Fire classification for the complete assembly, not just the slat.
- Formaldehyde class of the MDF (E0 or E1) and the test report number.
- Color, finish, batch tolerance and packing method.
The most common acoustic mistake in project sales is promising a quiet room because the wall panel says NRC 0.85. Absorption and insulation are different physics. Sell the panel for what it does, add the mineral wool and the cavity, and put the test report in the submittal.
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