A micro-perforated panel with three backing chambers held its absorption coefficient at 0.8 or above from 4 Hz to 1595 Hz in an optimized model, a span of 8.6 octave bands, against the 1-2 octaves a common single-layer panel covers. That gap explains most of what has happened to the micro-perforated absorber (MPA, or MPP) since D.-Y. Maa published its theory in 1975: the hole stayed under a millimetre, and the engineering moved into the cavity behind it. A 47 mm multi-chamber prototype now measures above 0.8 from 397 to 1000 Hz, and transparent acrylic MPPs have cut a classroom’s reverberation time from about 2 s to 1.1 s. Output keeps rising too, with 82 acoustics papers carrying the term in their title in 2025. We aggregated data from Maa’s 1998 JASA paper, Scientific Reports, AIP Advances, the International Journal of Environmental Research and Public Health, Fraunhofer IBP, INTER-NOISE and NOISE-CON proceedings, and the OpenAlex research index. For the wider family of engineered absorbers, see our acoustic metamaterials statistics.
TL;DR
- A typical MPP is under 1 mm thick, with holes under 1 mm and an opening ratio under 1% (Sakagami et al., UCL Open Environment 2021).
- Maa projected bandwidths of up to 3 or 4 octaves and pointed to holes of about 0.1-0.3 mm (Maa, JASA 1998).
- A common single-layer MPP absorbs over only 1-2 octaves (Liu et al., INTER-NOISE 2006).
- A modelled three-chamber MPP held α of 0.8 or more from 4 to 1595 Hz, or 8.6 octave bands (Wang, Liang and Mei, arXiv 2023).
- A 47 mm multi-chamber MPP measured α above 0.8 from 397 to 1000 Hz, at 1/18.2 of the wavelength (Wang and Bennett, AIP Advances 2024).
- Coiled cavities raised measured average absorption over 400-1600 Hz from 0.79 to 0.91 (Min et al., Scientific Reports 2025).
- Transparent acrylic MPP cut a classroom’s average reverberation time to 1.1 s, from about 2 s (Fasllija and Yilmazer, IJERPH 2023).
- A natural-fiber MPP alone peaked at 0.48, but on a porous backing the system averaged 0.788 (Nakhaeipour et al., Scientific Reports 2026).
- A new wood-based MPP is made of 92% natural ingredients (Nocke, NOISE-CON 2025).
- OpenAlex lists 82 acoustics papers with the term in the title in 2025, against 32 in 2015 (OpenAlex 2026).
1. Maa’s Design Rules: Hole Size, Perforation Ratio and Panel Thickness
Maa’s idea was to make the hole itself the absorber. When the diameter falls to a few times the viscous boundary layer, the panel supplies both the acoustic resistance and the low mass reactance a broadband absorber needs, so no fibrous filling is needed. His 1998 paper in the Journal of the Acoustical Society of America pointed to holes of about 0.1-0.3 mm and said making them in bulk still had to be solved.
Two decades later, published panels still follow the same recipe. A 2021 case study in UCL Open Environment summarises the typical MPP as under 1 mm thick, with holes under 1 mm and an opening ratio under 1%. The recent lab builds in the table below use 0.4-0.9 mm holes at 1.0-1.8% perforation, close to Maa’s range. What changed is the fabrication: laser drilling and 3D printing now make holes that were a manufacturing problem in 1998.
| Metric | Value | Source |
|---|---|---|
| Typical MPP definition | Panel under 1 mm thick, holes under 1 mm, opening ratio under 1% | Sakagami et al., UCL Open Environment 2021 |
| Hole size Maa named as still needing fabrication development | About 0.1-0.3 mm | Maa, JASA 1998 |
| Validity range of Maa’s original hole-impedance approximation | 1 < s < 10 (s = hole diameter over viscous boundary-layer thickness) | CSIC, Acoustics (MDPI) 2021 |
| Perforations a practical MPP needs | Hundreds of thousands per square metre | CSIC, Acoustics (MDPI) 2021 |
| 3D-printed PA12 multilayer MPP parameters | 0.9 mm holes, 1.0% perforation, 1 mm panel | Yang et al., Polymers 2020 |
| Coiled-cavity MPP parameters | 0.4 mm holes, 0.4 mm panel, 1.8% perforation | Min et al., Scientific Reports 2025 |
| Pore size recommended for better absorption above about 800-850 Hz | Below 0.5 mm | Deepak et al., Heliyon 2024 |
Context: Maa’s design formulas link three quantities, the perforate constant k, the relative resistance r and the peak frequency f0, so a target absorption curve maps directly to hole size, panel thickness and perforation ratio. Most of these numbers come from normal-incidence impedance tubes, not full-room tests, a measurement distinction covered in our anechoic chamber testing statistics. Most recent available data for the CSIC parameter study: Acoustics (MDPI), 2021.
2. Peak Absorption and the Single-Layer Bandwidth Ceiling
The classic MPP tradeoff is that it can absorb almost all the sound at one frequency but only over a narrow band. A common single-layer MPP covers only 1-2 octaves of bandwidth, according to an INTER-NOISE 2006 review by Liu et al., and that review links the peak coefficient directly to how far the band can stretch. Shrinking the holes is the main lever a single layer has. The same review reports 3-4 octaves as diameters fall.
The practical ceiling is lower than the theoretical one. A CSIC parameter study in Acoustics (MDPI) notes that a single layer only clears two octaves at medium-high frequencies with holes under 0.15 mm and perforation above 20%. Conventional MPPs still struggle below 500 Hz. High single peaks are easy to build. Getting a wide plateau out of one panel is not.
| Metric | Value | Source |
|---|---|---|
| Bandwidth of a common single-layer MPP | 1-2 octaves | Liu et al., INTER-NOISE 2006 |
| Bandwidth as micro-hole diameters decrease | 3-4 octaves | Liu et al., INTER-NOISE 2006 |
| Bandwidth Maa projected for MPP absorbers | Up to 3 or 4 octaves | Maa, JASA 1998 |
| Geometry needed to exceed two octaves with one layer | Holes under 0.15 mm, perforation above 20% | CSIC, Acoustics (MDPI) 2021, citing Qian et al. |
| Conventional MPP low-frequency limit | Limited absorption below 500 Hz | CSIC, Acoustics (MDPI) 2021 |
| Measured peak, 6 mm spiral-slit panel (0.44 mm slits, 16% perforation) | α = 0.88 at 1200 Hz | CSIC, Acoustics (MDPI) 2021 |
Outlier note: the 1-2 octave and 3-4 octave figures come from 2006 and 1998 respectively. Most recent available data: Liu et al., INTER-NOISE 2006, and Maa, JASA 1998. They remain the reference values recent papers cite.
3. Double-Layer, Multi-Cavity and Backing-Cavity Effects
Once the hole is fixed, the cavity becomes the tuning tool. Every extra chamber of a different depth adds a resonance, and the absorption peaks merge into a plateau. An optimized three-chamber model kept α at or above 0.8 from 4 to 1595 Hz, or 8.6 octave bands, up from 5.6 octaves before optimization (Wang, Liang and Mei, arXiv 2023). That is a preprint model figure, not a measured product.
The measured prototypes are more modest but still clearly better than a single layer. A Trinity College Dublin multi-chamber design in AIP Advances is 47 mm thick, which is 1/18.2 of the wavelength at its lowest working frequency. Coiled cavities in Scientific Reports (2025) fold resonators up to 135 mm long into an absorber that stays below 65 mm. The tradeoff is the same in every design: more bandwidth or more low-frequency reach, paid for in depth. That is why low-frequency problems, covered in our low-frequency HVAC noise statistics, remain hard to solve with thin panels.
| Metric | Value | Source |
|---|---|---|
| Three-chamber MPP, band with α of 0.8 or more, before optimization | 27-1304 Hz (5.6 octave bands) | Wang, Liang and Mei, arXiv 2023 |
| Three-chamber MPP, band with α of 0.8 or more, after optimization | 4-1595 Hz (8.6 octave bands) | Wang, Liang and Mei, arXiv 2023 |
| Multi-chamber MPP, measured bands with α above 0.8 | 397-1000 Hz and 698-1895 Hz | Wang and Bennett, AIP Advances 2024 |
| Multi-chamber MPP thickness | 47 mm (1/18.2 of the wavelength at the lowest operating frequency) | Wang and Bennett, AIP Advances 2024 |
| Coiled-cavity MPP, measured average α over 400-1600 Hz | 0.91 optimized vs 0.79 pre-optimization (peak 0.98) | Min et al., Scientific Reports 2025 |
| 20 mm unequal-cross-section series MPP | α above 0.5 from 1000-3450 Hz, three peaks reaching 1 | Jv et al., Materials 2024 |
| Two-layer unequal cross-section vs conventional series of the same thickness | First peak 0.82 to 0.95; trough 0.47 to 0.65 | Jv et al., Materials 2024 |
| Backing-cavity depth conventional broadband MPPs usually need | More than 5 cm | Singh et al., Scientific Reports 2022 |
Context: a 3D-printed PA12 study found the optimized triple-layer design’s theoretical frequency coverage (area under the absorption curve) of 311.9, against 282.9 for the best single layer. That is about 10% more: (311.9 - 282.9) / 282.9 = 10.3% (Yang et al., Polymers 2020). Most recent available data for that comparison: 2020.
4. Transparent and Glass MPPs in Buildings
Transparency is what made MPPs an architectural product rather than a lab curiosity. Glass and acrylic cannot be faced with a porous absorber without losing their transparency, but they can be perforated. Christian Nocke’s 50-year review in NOISE-CON 2025 proceedings dates micro-perforation of transparent sheets to 2000, followed by stretched-foil daylight ceilings and glass facades. Fraunhofer IBP lists a microperforated acrylic glass absorber tuned to 125 Hz-1 kHz and licensed to industrial partners.
The best-documented field result comes from a classroom. About 25 m² of transparent acrylic MPP cut the average reverberation time from about 2 s to 1.1 s over 250-1000 Hz (Fasllija and Yilmazer, IJERPH 2023). That still missed the 0.8 s target, so the panels alone could not finish the job, but the speech transmission index moved from 0.48 to 0.55. The same logic applies to glazed offices, where speech is the main distraction (see our open-plan office distraction statistics).
| Metric | Value | Source |
|---|---|---|
| Classroom treatment | Nine 1200 x 2400 mm transparent acrylic MPP panels, about 25 m² of side wall | Fasllija and Yilmazer, IJERPH 2023 |
| Reverberation time and STI, before and after | About 2 s to 1.1 s (250-1000 Hz average), target 0.8 s or less for rooms under 250 m³; STI 0.48 to 0.55 at receiver R1 | Fasllija and Yilmazer, IJERPH 2023 |
| Measured α, parallel-arranged acrylic MPP prototype | 0.89 at 400 Hz; above 0.5 from about 300-1250 Hz | Fasllija and Yilmazer, IJERPH 2023 |
| Desktop acrylic MPP partition, peak absorption per unit area | 0.33 at 1000 Hz (unperforated acrylic panel 0.02 or less) | Sakagami et al., UCL Open Environment 2021 |
| Desktop partition build | 2 mm acrylic MPP, 15 mm air layer, about 36 mm total | Sakagami et al., UCL Open Environment 2021 |
| Fraunhofer IBP microperforated acrylic glass absorber range | 125 Hz-1 kHz | Fraunhofer IBP, Acoustic Elements 2026 |
| Year micro-perforation was applied to transparent sheets | 2000 | Nocke, NOISE-CON 2025 |
Outlier note: the classroom panels used holes from 0.7 to 2 mm, so not every hole met the sub-millimetre rule, and the room was about 10 m by 5.5 m. Most recent available data for the classroom and desktop cases: 2023 and 2021.
5. MPPs vs Porous Absorbers: Hybrids, Materials and Manufacturing
MPPs were sold as the clean alternative to mineral wool, but a 2026 study shows the two work best together. In a Scientific Reports study, a natural-fiber MPP on an optimized porous backing reached a sound absorption average of 0.788, a 3.8% gain over the backing alone, while the panel by itself had peaked at only 0.48. The MPP extends the porous layer’s range downward, and the porous layer fills in around the MPP’s narrow band. The gain is modest on average, but the hybrid’s absorption stays above 0.90 over more than two octaves.
The materials are changing too. Nocke’s 2025 review describes a wood-based MPP made of 92% natural ingredients replacing petroleum-based sheets. Precision is still a constraint: in one 2025 build, 0.4 mm orifices came out within about ±10% of their design size, enough to shift a tuned peak.
| Metric | Value | Source |
|---|---|---|
| Natural-fiber MPP specification and solo performance | 1.2 mm flax and rice-husk panel, 500 μm holes, 1.613% perforation; peak 0.48 at about 780 Hz alone | Nakhaeipour et al., Scientific Reports 2026 |
| Optimized polyurethane-fibrogranule backing alone (40 mm) | Sound absorption average 0.759 (plain 40 mm composite about 0.58-0.60) | Nakhaeipour et al., Scientific Reports 2026 |
| Hybrid MPP plus porous backing | Sound absorption average 0.788; α above 0.90 from 480-2150 Hz | Nakhaeipour et al., Scientific Reports 2026 |
| Wood-based MPP composition | 92% natural ingredients | Nocke, NOISE-CON 2025 |
| Machining error on 0.4 mm orifices | About ±10% vs design | Min et al., Scientific Reports 2025 |
| Selective laser sintering settings for printed MPPs | 0.12 mm layer thickness, 40 W laser power | Yang et al., Polymers 2020 |
| Methods that made micrometre-scale holes practical | Laser drilling, powder metallurgy, welded meshing, electro-etching | Liu et al., INTER-NOISE 2006 |
6. Research Momentum and Adoption Signals
No audited market-size figure for micro-perforated absorbers is publicly available, so adoption has to be read from research and product signals. Those signals are clear. OpenAlex indexes 898 acoustics works with micro-perforated or microperforated in the title, and 82 of them appeared in 2025, compared with 32 in 2015, about 2.6 times more (82 / 32 = 2.56) (OpenAlex, 2026 query). Maa’s 1998 paper alone has 1,296 citations (OpenAlex work record).
The research is also maturing into reviews. A 2026 systematic review in Engineering Journal analysed 61 recent studies of structural and geometric MPP enhancements, finding cavity strategies most effective for low frequencies and panel modifications most flexible for tuning. On the industry side, four of the 16 product developments on Fraunhofer IBP’s acoustic-elements page are microperforated.
| Metric | Value | Source |
|---|---|---|
| Citations of Maa’s 1998 JASA paper | 1,296 | OpenAlex, 2026 |
| Acoustics works with micro-perforated or microperforated in the title, all years | 898 | OpenAlex, 2026 |
| Works published in 2025, 2024 and 2015 | 82, 76 and 32 | OpenAlex, 2026 |
| Studies analysed in a 2026 systematic review of MPP enhancements | 61 | Gilok and Ooi, Engineering Journal 2026 |
| Microperforated items among Fraunhofer IBP’s listed acoustic product developments | 4 of 16 (acrylic glass, foil, vehicle silencer, glass) | Fraunhofer IBP, Acoustic Elements 2026 |
| Time since Maa introduced MPA theory | About 50 years (1975) | Nocke, NOISE-CON 2025 |
Context: the OpenAlex counts are title matches filtered to the Acoustics concept, so they undercount papers that use terms like “perforated panel” only in the abstract. The 2026 figure (46 at the time of the query) is partial.
Summary: Micro-Perforated Absorbers by the Numbers
| Metric | Value | Source |
|---|---|---|
| Typical MPP definition | Under 1 mm thick, holes under 1 mm, opening ratio under 1% | Sakagami et al., UCL Open Environment 2021 |
| Bandwidth Maa projected | Up to 3 or 4 octaves | Maa, JASA 1998 |
| Common single-layer MPP bandwidth | 1-2 octaves | Liu et al., INTER-NOISE 2006 |
| Single-layer geometry to exceed two octaves | Holes under 0.15 mm, perforation above 20% | CSIC, Acoustics (MDPI) 2021 |
| Optimized three-chamber model, α of 0.8 or more | 4-1595 Hz (8.6 octave bands) | Wang, Liang and Mei, arXiv 2023 |
| Multi-chamber prototype, measured α above 0.8 | 397-1000 Hz at 47 mm thickness | Wang and Bennett, AIP Advances 2024 |
| Coiled-cavity MPP average α, 400-1600 Hz | 0.91 (vs 0.79 pre-optimization) | Min et al., Scientific Reports 2025 |
| 20 mm series MPP | α above 0.5 from 1000-3450 Hz | Jv et al., Materials 2024 |
| Unequal cross-section two-layer MPP, first peak vs conventional series | 0.82 to 0.95 | Jv et al., Materials 2024 |
| Typical backing cavity for broadband MPPs | More than 5 cm | Singh et al., Scientific Reports 2022 |
| Pore size for better absorption above about 800-850 Hz | Below 0.5 mm | Deepak et al., Heliyon 2024 |
| Classroom reverberation time with transparent MPP | About 2 s to 1.1 s | Fasllija and Yilmazer, IJERPH 2023 |
| Fraunhofer IBP acrylic glass MPP range | 125 Hz-1 kHz | Fraunhofer IBP, Acoustic Elements 2026 |
| MPP plus porous backing, sound absorption average | 0.788 (+3.8% vs backing alone) | Nakhaeipour et al., Scientific Reports 2026 |
| Wood-based MPP natural content | 92% | Nocke, NOISE-CON 2025 |
| MPP acoustics papers in 2025 | 82 | OpenAlex, 2026 |
| Studies in a 2026 systematic review of MPP enhancements | 61 | Gilok and Ooi, Engineering Journal 2026 |
Methodology and Sources
- Maa, D.-Y., Potential of microperforated panel absorber, Journal of the Acoustical Society of America 104(5), 1998: doi.org/10.1121/1.423870
- Liu, Tian, Jiao, Gu, Ball and Jiang, Advance in micro-perforated-panel sound absorbers, INTER-NOISE 2006: University of Huddersfield repository
- CSIC (ITEFI), Modelling of Microperforated Panel Absorbers with Circular and Slit Hole Geometries, Acoustics (MDPI) 2021: doi.org/10.3390/acoustics3040042
- Sakagami, Kusaka, Okuzono, Kido and Yamaguchi, Application of transparent microperforated panels to acrylic partitions for desktop use, UCL Open Environment 2021: doi.org/10.14324/111.444/ucloe.000021
- Fasllija and Yilmazer, Investigating the Potential of Transparent Parallel-Arranged Micro-Perforated Panels as Sound Absorbers in Classrooms, IJERPH 2023: doi.org/10.3390/ijerph20021445
- Wang, Liang and Mei, Optimization design of a micro-perforated panel absorber with 8.6 octave bands, arXiv 2023: arXiv 2305.18298
- Wang and Bennett, Ultra-broadband sound absorption in a compact multi-chamber micro-perforated panel absorber with varying depths, AIP Advances 2024: doi.org/10.1063/5.0187328
- Min, Lou and Zhao, Optimization of parallel coiled cavities of different depths in microperforated panel sound absorbers, Scientific Reports 2025: doi.org/10.1038/s41598-025-85171-3
- Jv, Wu, Mao, Li and Zhang, Light and thin broadband sound absorption structure based on unequal-cross-section microperforated plate series connection, Materials 2024: doi.org/10.3390/ma17246282
- Deepak, Pitchaimani, Nadimpalli and Mailan Chinnapandi, Exploring the acoustic potential of 3D printed micro-perforated panels, Heliyon 2024: doi.org/10.1016/j.heliyon.2024.e28612
- Yang et al., 3D Printing of Polymeric Multi-Layer Micro-Perforated Panels for Tunable Wideband Sound Absorption, Polymers 2020: doi.org/10.3390/polym12020360
- Singh, Prakash and Bhattacharya, Hybrid fractal acoustic metamaterials based on cross mixed micro-perforated panels, Scientific Reports 2022: doi.org/10.1038/s41598-022-24621-8
- Nakhaeipour, Forouharmajd, Habibi, Soltani and Tehrani, Acoustic performance optimization of natural-fiber micro-perforated panels backed by an optimized polyurethane-fibrogranule composite, Scientific Reports 2026: doi.org/10.1038/s41598-026-35058-8
- Nocke, Review on 50 years micro-perforated sound absorbers, NOISE-CON 2025 proceedings: doi.org/10.3397/in_2025_1075009
- Gilok and Ooi, Structural and Geometric Enhancements of Microperforated Panel Absorbers: A Systematic Literature Review, Engineering Journal 2026: doi.org/10.4186/ej.2026.30.3.41
- Fraunhofer Institute for Building Physics IBP, Acoustic Elements product developments page, accessed October 2026: ibp.fraunhofer.de
- OpenAlex research index, title search for micro-perforated or microperforated filtered to the Acoustics concept, grouped by year, and the work record for Maa (1998), queried October 2026: OpenAlex query
- Data watch: several foundational figures are older than three years (Maa 1998, Liu et al. 2006, Yang et al. 2020, CSIC 2021, Sakagami et al. 2021, Singh et al. 2022, Fasllija and Yilmazer 2023) and are flagged as most recent available data. The 8.6-octave result is an optimized model in an arXiv preprint, not a measured product. Some sources are internally inconsistent: Nakhaeipour et al. give a sound absorption average of 0.82 in the abstract but 0.788 in the results (we use 0.788); Jv et al. give 3450 Hz in the abstract and 3500 Hz in the conclusion; Wang and Bennett give 1895 Hz in the abstract and 2000 Hz in the body. Most values are normal-incidence impedance-tube measurements, which usually differ from random-incidence room results. No public, methodology-backed market-size estimate for micro-perforated absorbers could be verified, so none is cited.
Last updated: October 18, 2026. We update this roundup quarterly, and the next refresh is expected when the INTER-NOISE 2026 proceedings are indexed and OpenAlex closes its 2026 publication count.