Guides / Ceiling Systems
A perforated ceiling panel is a sheet with holes punched through it, and the holes are only the front door: the absorption happens in what sits behind them and in the cavity the panel closes. This guide sets out how the pattern is measured, how open area follows from hole diameter and hole centres, what belongs behind the panel, and what to put on the drawing so the acoustic build-up survives quotation, production and delivery.
Perforation does not absorb sound by itself: it makes the panel transparent to the absorber behind it. A perforated sheet over a sealed void behaves as a resonator and absorbs in a narrow band; the same sheet over mineral infill in a cavity of the right depth absorbs across the speech range. So the two things a drawing has to carry are the open area, which is pure geometry — for a 60° staggered pattern, 90.69 × (hole diameter ÷ centres)², read as a percentage — and the build-up behind the panel.
No panel, and no hole pattern, can be given an absorption figure on its own. The figure belongs to a tested assembly, and the rest of this page is about getting that assembly onto the drawing rather than losing it somewhere between the quote and the container.
On an aluminium ceiling the word covers a family rather than one product. The ceiling and facade systems range lists perforated panels alongside solid, corrugated and watchband profile panels, and within the perforated family it separates three levels of pattern:
In the specification table, perforation is listed as optional across the standard modules — 300 × 300, 300 × 600, 600 × 600, 600 × 1200 and 800 × 800 mm — with edge heights of 20, 24, 28 or 30 mm. That matters acoustically: the module decides how much of the face can be perforated and how much has to stay solid at the edge, and it decides which grid the panel hangs from.
Two neighbouring systems are often confused with it. An open cell ceiling is not perforated at all — it is a grid, mesh or woven-strip structure with a free area of 50 to 90 per cent and no panel face to punch. A baffle ceiling puts the absorber inside vertical blades, so its acoustic figure is attached to blade depth, spacing and infill rather than to a hole pattern. The differences are set out in the linear, baffle or cell comparison.
Open area — the proportion of the sheet that is hole rather than metal — is the one part of a perforated ceiling that is not a matter of opinion. For round holes on 60° staggered centres, the industry formula is:
open area (%) = 90.69 × (hole diameter ÷ centre spacing)²
For straight or 45° centres the constant is 78.54 instead of 90.69. Because the ratio is squared, tightening the pitch moves the number much faster than enlarging the hole: going from 6 mm to 5 mm centres at a 3 mm hole takes the open area from 22.7 per cent to 32.6 per cent, while going from a 3 mm to a 4 mm hole at 6 mm centres takes it to 40.3 per cent.
| Hole | Centres | Open area | Weight of 1.0 mm sheet |
|---|---|---|---|
| 1 mm hole | 3 mm centres | 10.1% | 2.43 kg |
| 1.5 mm hole | 4 mm centres | 12.8% | 2.36 kg |
| 2 mm hole | 5 mm centres | 14.5% | 2.31 kg |
| 3 mm hole | 6 mm centres | 22.7% | 2.09 kg |
| 3 mm hole | 5 mm centres | 32.6% | 1.82 kg |
| 4 mm hole | 6 mm centres | 40.3% | 1.61 kg |
The open area column is arithmetic from the formula above. The weight column applies that same open area to solid aluminium at 2.70 kg per square metre per millimetre — the density of aluminium, 2,700 kg/m³, in EN 1999-1-1 — and is the flat face only, without the downturned edge. The full build-up is covered in what a suspended ceiling weighs per m².
Two habits follow from this. First, an open area on its own is not a specification: 22.7 per cent made of 3 mm holes at 6 mm centres is a different absorber from 22.7 per cent made of 1 mm holes at 2 mm centres, because the hole is the entrance to the cavity and its size sets which frequencies pass. Second, a pattern image cannot be quoted — the drawing has to state the diameter, the centres and the pattern, and the percentage should be shown as calculated from them.
This is where perforated ceilings are most often lost. The panel is quoted, the absorber is not, and nobody notices until the room is handed over. Four things can sit behind a perforated face, and only two of them absorb:
| Behind the panel | What it does | What it does not do |
|---|---|---|
| Bonded acoustic fleece or black tissue | Adds a controlled resistive layer right behind the holes and keeps dust and paint out of the cavity | Does not replace the cavity absorber on its own |
| Mineral or glass-fibre infill in the cavity | The porous absorber the perforation exposes; depth and density set which frequencies are absorbed | Not a load-bearing element, and it has to be retained so it does not settle |
| Foil-faced or sealed insulation | Thermal and condensation control in the void | Reflects sound back through the holes instead of absorbing it |
| Empty sealed cavity | Behaves as a resonator at a narrow band set by hole size, open area and cavity depth | Cannot be given a broadband absorption figure |
An acoustic fleece bonded to the back of the panel is the layer that keeps the build-up repeatable: it stops dust and paint reaching the cavity, and it gives the facing a controlled resistance. It does not replace the cavity absorber. Mineral or glass-fibre infill in the cavity is what actually absorbs, and its depth and density set which part of the spectrum is covered — which is why the cavity depth belongs on the drawing next to the panel thickness.
Foil-faced insulation deserves a separate warning because it looks like acoustic insulation and is not. Its purpose is thermal and condensation control in the void; the foil face reflects sound back through the holes, so a ceiling built with it can be fully “insulated” and still sound like a solid soffit. If both are needed, they go in as two layers, in the right order.
Two suppliers can send the same perforated panel with the same open area and produce rooms that sound nothing alike. The variables that move the result are known, and all of them can be written down:
| Variable | Why it matters |
|---|---|
| Hole diameter and pattern | A 3 mm hole and a 6 mm hole at the same open area do not absorb the same way |
| Open area | Sets how much sound reaches the absorber, and how much metal is left in the face |
| Sheet thickness | The depth of the hole is the thickness of the panel, which changes the acoustic mass of the facing |
| Cavity depth | The air space behind the panel is part of the absorber, not empty space |
| What fills the cavity | Fleece, mineral infill, foil facing or nothing |
| Perimeter and plenum | An unsealed edge or an open return lets sound bypass the absorber |
One practical consequence: a plenum full of ducts, cable trays and open returns is not the sealed cavity a laboratory specimen was tested in. Services crossing the void are fine, but the perimeter detail and the returns have to close the cavity, or the absorber is bypassed and the perforation is doing nothing but decorating the ceiling.
The choice between standard and micro-perforation is usually a visual one, and it has two acoustic consequences. To reach the same open area with smaller holes, the centres have to come in proportionally — halve the diameter and the pitch has to halve with it — so a micro-perforated sheet is a finer punching job with tighter tolerance and a higher unit cost for the same performance. The payoff is a face that stays visually continuous, which is why micro-perforation appears on ceilings where the pattern would otherwise compete with the architecture.
The second consequence is maintenance. Paint bridges small holes and clogs the facing, and ceiling manufacturers state that the declared absorption coefficients and the fire properties deteriorate once a ceiling is repainted. A micro-perforated ceiling is the most exposed to this, because the holes are the smallest. Two things prevent it: an unperforated margin left where the panel turns into the edge detail, and a finish schedule that says how the ceiling may be redecorated. On the supply side, the coating is applied after perforation to the specification on the order, and the coating system is stated on the quotation so it can be matched later.
A perforated panel is a sheet with metal removed, so it is less stiff than the solid sheet it started as, and the loss follows the open area and the direction of the pattern. That is not a reason to avoid perforation; it is a reason to specify the module and the thickness together. The face is carried by the downturned edge and by the grid, the perforated field normally stops short of the edge, and the panel is specified on a module the grid can support — the standard modules run from 300 × 300 to 800 × 800 mm, with the aluminium between 0.6 mm and 3.0 mm.
Weight is the other panel-level effect, and it can be calculated: the open area is the fraction of metal that is missing, so one millimetre of aluminium at 2.70 kg per square metre falls to 2.09 kg per square metre at 22.7 per cent open area, and to 1.61 kg at 40.3 per cent. Carrying that into the load on the soffit is the subject of the weight per m² guide, which also covers the grid, the hangers and the infill as separate line items.
Absorption is measured, not asserted. In Europe the measurement is made in a reverberation room to ISO 354 and rated to EN ISO 11654, which reduces the curve to a weighted coefficient and groups it into a class from A to E; in the United States the same measurement is reported to ASTM C423 as NRC or SAA. How each of those single numbers is derived, and what the class boundaries are, is set out in the baffle ceiling rating section — the arithmetic is the same for a perforated panel.
What matters here is what the report has to name. A rating printed next to a panel on its own is not usable, because the same panel over different cavities gives different numbers. The report should identify the panel module and thickness, the hole diameter, the centres and the open area, the backing, the cavity depth and infill, and how the specimen was mounted. Given those, the figure can be checked against the build-up you are actually buying; without them, it is a number about a different ceiling.
And because every one of these ratings is an average over a band, two build-ups with the same figure can behave differently at low frequency — usually where a room feels boomy. Where the problem is low-frequency, ask for the absorption curve rather than the single number.
If a perforated ceiling is specified as “perforated” and nothing else, the quote defaults to a standard pattern with no backing — and the acoustic layer disappears without anyone deciding to remove it. Eleven lines close that gap:
| Item | What to state | Why it has to be on the drawing |
|---|---|---|
| Panel module and edge | 300 x 300 up to 800 x 800 mm, plus the edge height (20 / 24 / 28 / 30 mm) | Sets the grid, the clip and the border that stays unperforated |
| Aluminium thickness | 0.6 to 3.0 mm | Drives stiffness, weight and the price step |
| Hole diameter | Stated in millimetres, not as a picture | Small holes and large holes behave differently at the same open area |
| Hole centres and pattern | Pitch in millimetres, 60-degree staggered or straight | Open area is calculated from this; a pattern image cannot be quoted |
| Open area | Percentage, and the calculation it came from | The one number the acoustic design is built on |
| Perforated field and margin | Where perforation stops at the edge | Keeps the edge detail and the clip line intact |
| Backing | Fleece or tissue bonded on the back, or none | The layer that turns a hole pattern into an absorber |
| Cavity and infill | Depth above the panel, absorber type and density | The absorber the perforation is there to expose |
| Plenum condition | Sealed void, open plenum, services crossing it | Leaks at the perimeter and open returns change the result |
| Finish | Powder coat, PVDF, anodized, wood-grain or stone-grain | Applied after perforation; heavy coats can bridge small holes |
| Area and destination | Total square metres and the port | Loading, packing and the validity of the quote |
A drawing with those lines on it can be quoted line by line, and two quotations can then be compared on the same build-up instead of on two different products. It also survives the handover from quotation to production: the punch tool, the infill and the coating are all set from the same sheet.
The perforated panel is one system inside the ceiling and facade range, alongside linear metal ceilings, baffle ceilings and open cell ceilings. Where the brief is a flat, continuous plane with absorption behind it, perforated is usually the answer; where airflow, access or a visible void matters more, one of the others is. The acoustic tile guide covers the module question for tiles, and the suspended panel pricing guide covers what a quotation itemises.
Documents a project can request before dispatch are listed on the certifications page, and how they are checked is on inspection. Send the drawing with the hole diameter, centres, backing and cavity on it, and the panel, the absorber and the trim come back as one quoted package. Send drawings and the destination port, or use the contact page.
They are metal ceiling panels with a pattern of holes punched through the face, used as the visible layer of an absorbing build-up. The perforation lets sound reach a porous absorber behind the panel instead of reflecting it back into the room. On its own the perforated sheet is a facing, not an absorber: the absorption comes from the material in the cavity and from how that cavity is closed at the edges.
No. A perforated panel over a sealed void behaves as a resonator and absorbs over a narrow band, which is rarely the brief. The same panel with mineral infill or a bonded fleece behind it, in a cavity of the right depth, absorbs across the speech range. Two quotes can carry the same perforated panel and give completely different acoustic results because one of them left the absorber out.
Open area is geometry. For round holes on 60-degree staggered centres it is 90.69 multiplied by the hole diameter divided by the centre spacing, squared, and read as a percentage. For straight or 45-degree centres the constant is 78.54 instead. A 3 mm hole at 6 mm centres gives 90.69 x 0.25 = 22.7 per cent, and a 3 mm hole at 5 mm centres gives 32.6 per cent. Because the ratio is squared, tightening the pitch moves the open area much faster than enlarging the hole.
Standard perforation is visible as a pattern from normal viewing distance. Micro-perforation uses holes small enough that the face reads as almost solid, which is why it is specified where the ceiling has to look continuous. The trade-off is pitch: to reach the same open area with smaller holes the centres have to come in proportionally, so a micro-perforated sheet is a finer and more demanding punching job, and the drawing has to state both the hole size and the centres rather than the open area alone.
One of three things, and the drawing should say which: an acoustic fleece or black tissue bonded to the back of the panel, a mineral or glass-fibre absorber laid in the cavity above it, or both. A foil-faced or sealed insulation board is not an absorber, because the foil reflects the sound back through the holes. An empty sealed cavity, or a plenum with gaps at the perimeter, will not perform as the same build-up tested in a laboratory.
It removes metal, so the face is less stiff than solid sheet of the same thickness, and the loss depends on the open area and on the pattern direction. That is why perforated panels are usually specified on a module that the grid and the downturned edge can carry, and why the perforated area is normally kept out of the edge detail. Weight falls with open area as well: one millimetre of aluminium is 2.70 kg per square metre solid, so a 22.7 per cent open area takes it to about 2.09 kg per square metre.
As a single-number rating attached to a tested build-up, never to the panel alone. In Europe absorption is measured in a reverberation room to ISO 354 and rated to EN ISO 11654 as a weighted coefficient with a class from A to E; in the United States the same measurement is reported to ASTM C423 as NRC or SAA. A rating is only usable if the test report names the panel, the hole pattern and open area, the backing, the cavity depth and the mounting.
Yes, and it is the one maintenance action that can quietly undo the specification. Paint bridges small holes and clogs the facing, and ceiling manufacturers state that the declared absorption coefficients and the fire properties deteriorate once a ceiling is repainted. If the ceiling has to be redecorated, the finish schedule should say how, and the coating should be checked against the perforation rather than applied over it.
Standards are cited for the definitions and methods they contain. The acoustic figure for a project comes from the test report for the build-up specified, not from this page.