Acoustic Thickness: Why Depth and Material Choice Define Performance
The word acoustic gets slapped on just about everything these days, slat panels, foams, and decorative wall features. But here’s the reality: performance depends on physics, not marketing. If you want real results, two factors matter most: thickness and material properties. Together, they determine which parts of the sound spectrum you actually control.
Why Thickness Matters?
Sound is vibration. Low-frequency sounds (like bass or deep voices) have long waves, while high-frequency sounds (like sharp consonants or treble) have short waves.
Short waves can be tamed with thin materials. Long waves need depth and density to be absorbed. Think of it like a sponge: a thin sponge only wipes the surface, while a thicker sponge soaks deeper. Acoustic panels work the same way.
General Thickness Guide
Here’s how thickness impacts performance:
Thin Backing (≤10 mm)
Absorbs mainly high frequencies (flutter echo, sharp reflections).
(Clinking cutlery or glasses → ~2,000–8,000 Hz)
Very little impact on speech clarity in the low–mid range.
Often marketed as “acoustic,” but the effect is limited.
Medium Thickness (25–50 mm)
Absorbs more of the human voice range (mid frequencies).
(Baby crying → ~500–1,200 Hz)
Noticeable improvements in classrooms, offices, and meeting rooms.
Works best when paired with reflective elements (like slats) that scatter sound to avoid creating a “dead” room.
Thick Absorbers (75–100 mm+)
Extend absorption into the low–mid range.
(Subwoofer/bass from a TV or music system → 60–120 Hz)
Essential for studios, music rooms, and performance spaces where balanced acoustics are critical.
Often paired with air cavities or dense insulation to control bass build-up.
Not All Acoustic Materials Are Created Equal
When you see the word acoustic on a product label, it doesn’t always mean the material inside is doing the same job. Different materials absorb, reflect, or diffuse sound in unique ways because of their density, structure, and thickness. Choosing the right one depends on the specific frequencies you need to control and the type of environment you’re treating.
Here’s how common acoustic materials behave:
Acoustic Foam
Lightweight, porous, and excellent at taming mid to high frequencies. It struggles with bass and low-mids unless it’s very thick. Foam is often marketed for studios, but unless depth is added, its performance is limited to treble and upper midrange.
Fiberglass
Similar in performance to mineral wool but often lighter and used in large scale applications like ceiling baffles, duct liners, and commercial panels. It’s highly effective but requires proper handling and casing for safety.
Perforated or Slotted Timber Panels
These are hybrid solutions: the timber face reflects and scatters sound, while the material behind (if it’s real insulation like mineral wool) does the absorbing. The performance depends entirely on what’s behind the wood the slats alone don’t do much.
Mineral Wool / Rockwool
Dense and fibrous, making it one of the most effective broadband absorbers. It handles everything from mids through low frequencies well, which is why it’s the go to material in professional acoustic panels and bass traps.
Polyester / PET Felt
Eco-friendly and usually made from recycled plastic bottles. It’s typically manufactured as a thin (6–12 mm) sheet, which means it mainly addresses high frequencies. It’s popular in decorative wall panels and slat panel backings, but without added depth, its effect is cosmetic more than functional.
Fabric-Wrapped Panels
A versatile format: the fabric is just the finish, while the inside is typically mineral wool or fibreglass. Their thickness can be customised to target specific ranges, thinner for offices (speech clarity), thicker for studios (low-mid control).
Case Study: The Truth About Slat Panels
Slat panels have become extremely popular in modern interiors—offices, restaurants, and even residential spaces. They’re often marketed as acoustic panels, implying they will improve sound quality significantly. But here’s the catch: not all slat panels perform like true acoustic absorbers.
Most commercially available slat panels come with a thin 9–12 mm PET felt backing. While this may slightly reduce harsh reflections and soften high-frequency sounds, it does very little to absorb mid or low frequencies, which are the ranges most critical for speech clarity and balanced room acoustics.
Adding to this, the timber slats themselves are highly reflective. Sound waves hit the surface and bounce back into the room rather than being absorbed. The gaps between the slats do allow some sound to reach the backing material—but with such a thin layer, only a small portion of the energy is absorbed.
What This Means in Practice
High frequencies (like the “s” and “t” sounds in speech, or clinking cutlery) are slightly softened.
Mid-range frequencies (the human voice, conversations, or TV audio) largely remain uncontrolled, which can make spaces feel echoey or harsh.
Low frequencies (bass hum, machinery, or traffic noise) pass through almost entirely.
The result is that these panels are often decorative first and acoustic second. They may improve aesthetics or reduce surface brightness, but they don’t solve real acoustic challenges unless they are paired with thicker insulation or a cavity behind the slats.
Many buyers expect Soundproofing, or Balanced acoustic control. What they actually get: Slight echo reduction, but no meaningful improvement to low or mid frequencies. This mismatch wastes budget and leaves the original acoustic problem unresolved. The Takeaway from this is that Not all “acoustic” panels are created equal. Thickness and density are what define performance. Always look for tested absorption data. Acoustics is physics, not decoration. If you want meaningful results, choose solutions based on material science, thickness, and proper installation, not just marketing buzzwords.
Why Work With ISS Acoustic & Interiors?
At ISS, we’ve installed partition wall systems across a wide range of commercial interiors from schools and healthcare facilities to corporate offices. With over 10 years of experience, our team works with premium partition systems and manages every aspect of installation efficiently and professionally.
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Whether you're looking to enhance privacy, improve acoustics, or redefine the layout of a space, partition walls offer a flexible and future proof solution. If you're considering partitions for your next commercial project, feel free to get in touch, we're happy to offer advice or provide a quote.
