50mm vs 25mm Acoustic Panels: Comparing Thickness and Performance

One of the most common questions when specifying acoustic panels is thickness. Is a 25mm panel enough, or is 50mm worth the extra depth? The answer affects acoustic performance, appearance, available space and budget — and it depends on what the room actually needs.

Thickness matters because porous acoustic panels absorb sound within their depth. A thicker panel gives sound more material to pass through, which generally improves absorption, especially towards the lower end of the frequency range. But thicker is not automatically better for every room.

AcouStick manufactures acoustic panels in KSA across a range of materials and thicknesses — including PET, fabric, wooden and wool panels — and sizes treatment through acoustic modelling and absorption calculations rather than guesswork.

This guide compares 25mm and 50mm acoustic panels, explains why thickness changes performance, shows published test data, and helps you choose the right thickness for your project.

Why Panel Thickness Affects Absorption

Most acoustic panels are porous absorbers. Sound energy entering the material is converted into a very small amount of heat by friction and thermal exchange in the fibres or pores. More depth means more material for the sound wave to pass through.

A 2026 peer-reviewed study in Results in Engineering by Khoshouei, Soltani, Khoshouei and Taban, which made panels from upcycled waste PET bottles, found absorption was strongly governed by thickness and bulk density, with enhanced absorption at greater thicknesses and an optimum density of around 180 kg/m³. Their panels showed typical porous behaviour, with absorption strongest in the mid-to-high frequencies.

Published Data: 25mm vs 50mm

Manufacturer test data for the same material at two thicknesses shows the effect clearly. Owens Corning's published data sheet for its 703 mineral fibre board (Pub. No. 10021736-H), tested to ASTM C423 with Type A mounting directly against a solid backing, reports:

25mm (1 inch) Board

• 125 Hz — absorption coefficient 0.05

• 250 Hz — absorption coefficient 0.26

• 500 Hz — absorption coefficient 0.63

• NRC — 0.70

50mm (2 inch) Board

• 125 Hz — absorption coefficient 0.15

• 250 Hz — absorption coefficient 0.71

• 500 Hz — absorption coefficient above 1.00 as reported

• NRC — 1.00

At higher frequencies (1000 – 4000 Hz) both thicknesses are reported as highly absorptive. The main difference is in the low and lower-mid frequencies: at 250 Hz, the 50mm board's reported coefficient is close to three times that of the 25mm board.

Key takeaway: doubling thickness from 25mm to 50mm mainly improves absorption at lower frequencies. At high frequencies, both can perform strongly.

These figures describe one specific product in one mounting. They illustrate the trend; they are not a substitute for the data sheet of the panel you intend to use.

Understanding the Ratings

• Absorption coefficient — the fraction of sound absorbed at a given frequency.

• NRC — under ASTM C423, the average at 250, 500, 1000 and 2000 Hz, rounded to 0.05 — it does not include 125 Hz.

• SAA — the average of twelve one-third octave bands from 200 to 2500 Hz.

• αw and classes — under ISO 11654, absorption classes run from A (αw 0.90 – 1.00) to E (0.15 – 0.25).

Because NRC excludes 125 Hz, two panels with similar NRC values can still differ noticeably in the bass. Always look at the full frequency data when low frequencies matter.

Mounting Can Matter as Much as Thickness

ASTM E795 states that the absorption of a material covering a flat surface depends not only on its physical properties but also on how it is mounted. Mounting a panel with an air space behind it, rather than directly on the wall, changes its measured performance. When comparing 25mm and 50mm panels, make sure both were tested in the same mounting — and in the mounting you will actually use.

25mm Acoustic Panels: Pros and Considerations

Advantages

• Slim profile — suits rooms where depth is limited.

• Lighter — easier handling and fixing.

• Strong mid and high frequency absorption — suitable for controlling speech reflections.

• Cost-conscious — less material per square metre.

Considerations

• Limited low-frequency absorption — as the published data shows.

• More area may be needed — to reach the same total absorption.

Typical Uses

• Offices and meeting rooms focused on speech

• Classrooms and training rooms

• Restaurants and hospitality interiors

• Corridors and reception areas

50mm Acoustic Panels: Pros and Considerations

Advantages

• Broader absorption — stronger performance at lower frequencies.

• Higher NRC — in the published data, 1.00 versus 0.70.

• Fewer panels may be needed — for the same absorption target.

Considerations

• Deeper profile — takes more space from the room.

• Heavier — fixing details must suit.

• Higher material cost — per square metre.

Typical Uses

• Recording studios, control rooms and home cinemas

• Auditoriums, multipurpose halls and mosques

• Gyms and sports halls

• Rooms with low-frequency or music-related problems

Is Thicker Always Better?

Not necessarily. The right thickness depends on:

• The frequencies that need control — speech-focused rooms may be well served by thinner panels; bass problems need thicker or deeper treatment.

• The amount of treatment needed — the Sabine equation (T = 0.161V / A) shows total absorption, not panel thickness alone, determines reverberation.

• The available surface area — more area at 25mm can sometimes match less area at 50mm at mid and high frequencies.

• Space and appearance — depth, weight and architectural finish.

• Budget — material and installation cost.

For very low frequencies, even 50mm may not be enough. In small rooms, a Warsaw University of Technology text gives the Schroeder frequency as f = 2000 √(T/V), below which room modes dominate and dedicated low-frequency treatment such as membrane absorbers or deep bass traps is usually needed.

How to Choose Between 25mm and 50mm

1. Define the problem — echo, reverberation, speech clarity or low-frequency boom?

2. Set the target — reverberation time for the room's use — for example ANSI/ASA S12.60 allows 0.6 s in small classrooms; EBU Tech 3276 specifies 0.2 – 0.4 s for listening rooms.

3. Check the frequencies — compare full absorption data, not just NRC.

4. Calculate quantities — use the Sabine equation to estimate how much absorption is needed at each thickness.

5. Compare mounting — same mounting for a fair comparison.

6. Consider practicality — space, weight, finish, fire classification and cost.

Other Selection Factors

• Fire classification — under ASTM E84, Class A is a flame spread index of 0–25 (Class B 26–75, Class C 76–200), each with a smoke-developed index of no more than 450.

• Density — Khoshouei et al. found both insufficient and excessive density reduced performance.

• Facing — fabric, PET felt, perforated or slotted timber affect appearance and performance.

• Durability and cleanability — important in healthcare, education and hospitality.

Panel Thickness in Saudi Projects

Saudi interiors often feature large volumes, high ceilings and hard finishes. In offices and meeting rooms, slimmer panels may integrate more easily with architectural finishes. In mosques, auditoriums, ballrooms and studios, where lower-frequency reverberation is more significant, thicker panels or deeper systems are often worth the extra depth. The right choice comes from the room's target and measured or calculated performance.

Common Mistakes

Mistake 1: Choosing by NRC Alone

NRC hides low-frequency differences.

Mistake 2: Comparing Different Mountings

Results depend on how panels are mounted.

Mistake 3: Expecting Panels to Soundproof

Neither thickness stops sound passing through walls.

Mistake 4: Ignoring Quantity and Placement

Total absorption and location matter as much as thickness.

Mistake 5: Using Thick Panels Everywhere

Unnecessary depth and cost where speech control is the only goal.

Checklist

• What frequencies need control?

• What is the reverberation target?

• Are full frequency data available for both thicknesses?

• Were both tested in the same mounting?

• How much area is available?

• Do panels meet fire and durability requirements?

How AcouStick Helps You Choose

AcouStick's engineering workflow includes RT60 prediction and absorption sizing, so panel thickness and quantity are selected against the target, then documented in specifications and shop drawings and supported on site. Its KSA-manufactured range includes:

• PET panels — slim panels for offices, restaurants, schools and studios

• Fabric and wooden panels — architectural finishes with absorptive cores

• Acoustic wool panels — deeper, high-performance absorption

• Bass treatment and diffusers — for studios and performance spaces

Frequently Asked Questions

1. Is a 50mm acoustic panel better than 25mm?

It generally absorbs more, especially at lower frequencies. Whether it is better depends on the room's needs, space and budget.

2. How much difference does thickness make?

In published Owens Corning 703 data, NRC rises from 0.70 at 1 inch to 1.00 at 2 inches, with the largest gains at 125 – 500 Hz.

3. Are 25mm panels enough for offices?

Often, for speech-focused rooms — provided enough area is treated to meet the reverberation target.

4. Do thicker panels help with bass?

They help, but strong low-frequency problems often need dedicated bass treatment.

5. Does mounting affect performance?

Yes. ASTM E795 states absorption depends on how the material is mounted.

6. Do thicker panels soundproof better?

No. Panels absorb sound inside a room; soundproofing requires sound insulation.

Final Takeaway

Moving from 25mm to 50mm mainly improves absorption at lower frequencies, as published test data shows. The right choice depends on the frequencies that matter, the reverberation target, the available area, the mounting and practical constraints — and is best decided by calculation rather than by thickness alone.

Not sure which panel thickness your project needs? Share your room details with AcouStick for an absorption calculation and recommendation.

If you are choosing between panel thicknesses, AcouStick can calculate the absorption your room needs and recommend the right panel.

Email: info@acoustick.co | Call: +966 51 130 809 | Web: www.acoustick.co

REFERENCES

• Khoshouei, P., Soltani, P., Khoshouei, P., & Taban, E. "Upcycling waste PET bottles into high-performance fiber/flake composite panels for sustainable acoustic and thermal insulation in buildings." Results in Engineering (ScienceDirect), 2026.

• Owens Corning. "Fiberglas 700 Series Insulation Product Data Sheet — Types 703 and 705," Pub. No. 10021736-H (2026) — ASTM C423 absorption coefficients for 1 in and 2 in boards, Type A mounting.

• ASTM International. ASTM C423, "Standard Test Method for Sound Absorption and Sound Absorption Coefficients by the Reverberation Room Method" — NRC and SAA definitions as summarised by Intertek: intertek.com/building/standards/astm-c423

• International Organization for Standardization. ISO 11654:1997, "Acoustics — Sound absorbers for use in buildings — Rating of sound absorption" — αw derivation and Annex B absorption classes (BS EN ISO 11654:1997 text).

• ASTM International. ASTM E795-16, "Standard Practices for Mounting Test Specimens During Sound Absorption Tests" — scope statement: store.astm.org/e0795-16.html

• ScienceDirect Topics. "Sabine Equation" — metric form T = 0.161V/A and the equation's origin: sciencedirect.com/topics/engineering/sabine-equation

• Fidecki, T. "Room Acoustics and Sound Reinforcement Systems." Warsaw University of Technology, Institute of Radioelectronics, course text — room mode and Schroeder frequency formulae: ire.pw.edu.pl

• ANSI/ASA S12.60-2010/Part 1 (R2020), "Acoustical Performance Criteria, Design Requirements, and Guidelines for Schools" — limits as summarised by Armstrong World Industries, "Classroom Acoustics and ANSI Standard S12.60": armstrong.com/en-us/articles/classroom-acoustics-ansi-standard.html

• European Broadcasting Union. EBU Tech 3276, "Listening conditions for the assessment of sound programme material: monophonic and two-channel stereophonic," 2nd edition, May 1998: tech.ebu.ch/docs/tech/tech3276.pdf

• ASTM International. ASTM E84, "Standard Test Method for Surface Burning Characteristics of Building Materials" — Class A/B/C thresholds as summarised by Intertek: intertek.com/building/standards/astm-e84