Researchers developed a sustainable acoustic metamaterial using cork membranes and honeycomb paper layers, achieving high low-frequency sound absorption with recyclable, eco-friendly materials — ideal for green building applications.
Noise pollution poses a significant threat beyond mere annoyance — it's a health hazard 🚧. As our cities grow noisier and buildings become more compact, engineers are under pressure to design acoustic solutions that don’t just work — they also respect the planet 🌍. Today, we’re diving into a fascinating study from Buildings journal that tackles both goals using two humble materials: cork and paper honeycomb 🐝.
Controlling sound — especially low-frequency noise (like traffic rumbles or machinery hums) — is notoriously difficult. Traditional solutions use thick, heavy, synthetic materials like polyurethane foam or fiberglass. But these come with drawbacks:
🌫️ High carbon footprints
🧯 Poor recyclability
🧱 Bulky installations
Enter acoustic metamaterials — specially engineered structures that manipulate sound in ways traditional materials can’t. Think of them as sonic wizards 🧙♂️. Now imagine if these metamaterials were also made from natural, sustainable resources… 🎯 That’s exactly what this new research delivers!
Made from the bark of the cork oak tree, this material is:
By stacking layers of cork membranes and honeycomb structures, the researchers created modular acoustic panels that can be tuned for different noise frequencies — kind of like assembling a Lego set of silence 🧱🔇.
Three metamaterial configurations were tested in a Kundt’s tube, which measures how well each one absorbs sound between 250 Hz and 1400 Hz (the zone where most indoor and urban noise lives):
📈 The more membranes they added, the better the results — more resonances, more energy absorption, wider bandwidth!
So how does it all work?
These structures mimic mass–spring–damper systems — like a car suspension, but for sound:
The researchers simulated this behavior using mathematical models in MATLAB — and their predictions matched the experiments closely ✅.
This combo creates “localized resonances” — hot zones where sound waves get trapped and absorbed efficiently. It’s especially effective at low frequencies, which are normally hard to tame without thick materials.
Traditional soundproofing often compromises sustainability. But this metamaterial delivers on both performance and eco-responsibility.
✅ Low environmental impact: No synthetic foams, plastics, or adhesives
✅ Lightweight and modular: Easy to install in ceilings, walls, or panels
✅ Scalable and customizable: Performance can be tuned by changing layer count
✅ Fully recyclable or biodegradable: Supports circular design principles ♻️
In real-world applications, this means better acoustic environments in:
📦 Offices
🏠 Homes
🛠️ Factories
🚌 Public transport
🧳 Packaging for sensitive electronics
It’s a big step for sustainable architecture, aligning with green certifications like LEED and WELL 🌿.
The researchers highlight some exciting future prospects:
🔹 Durability Testing: Cork is resilient, but long-term performance in harsh environments (humidity, temperature) needs more study.
🔹 High-Frequency Absorption: Current setups work best for low/mid-range. Can this tech be pushed into higher ranges?
🔹 Real-World Installations: From labs to living rooms — future tests will explore how these panels perform in reverberation rooms and actual buildings 🏢.
🔹 Design Variability: Think custom shapes, dynamic tuning, or hybrid systems that combine cork-honeycomb layers with other green materials like coir, jute, or bio-resins 🌾
This research doesn’t just present another material — it offers a new mindset for acoustic design:
🎯 Performance + 🌍 Sustainability = 💡 Smart Engineering
By turning to nature's own materials, and cleverly engineering them into acoustic metamaterials, this study unlocks a powerful solution to the noise challenges of modern life — while keeping our planet in mind 💚.
And best of all? It proves that eco-friendly doesn’t mean underperforming. In fact, the greenest choice might just be the smartest one. 🌟
🔊 Acoustic Metamaterials - Materials engineered to control sound in ways nature can't. They bend, absorb, or block sound waves using clever internal structures, not just their composition.
🌱 Sustainable Materials - Eco-friendly materials that are renewable, recyclable, or biodegradable. Think cork, bamboo, or recycled paper — kind to the planet and often surprisingly strong!
🟤 Cork Membrane - A thin, flexible sheet made from cork bark. Cork is elastic, lightweight, and great at soaking up sound, making it perfect for acoustic applications.
🐝 Honeycomb Structure - A pattern of hexagonal cells, like a beehive, made from stiff materials like aramid paper. It’s super strong yet light, and in acoustics, it helps trap and dampen sound waves. - More about this concept in the article "Bio-Inspired Engineering: Transforming Reinforced Concrete Protection with Honeycomb Structures 🐝".
📉 Sound Absorption Coefficient (SAC) - A number between 0 and 1 showing how well a material absorbs sound. 1 means total absorption (like a sound sponge 🧽), 0 means total reflection (like a wall).
🔁 Resonance - When something vibrates more at certain frequencies. Like how a guitar string has a “sweet spot” — materials can have these too for sound waves! - More about this concept in the article "Revolutionizing Diabetes Care: The 3D-Printed Sensor Changing Glucose Monitoring 🍭 🩸".
⚙️ Mass–Spring–Damper System - A physics model that mimics how things move and vibrate. Used to simulate how membranes and air layers in materials respond to sound energy.
📏 Kundt’s Tube (Impedance Tube) - A lab tool for testing how much sound a material absorbs. Sound waves are sent down a tube, hit the sample, and bounce back — sensors measure what’s absorbed vs. reflected.
🧱 Helmholtz Resonator - A sound-absorbing device made from a cavity and an opening. Think of blowing across a bottle — that same trapped-air effect helps absorb certain sound frequencies.
🏗️ Green Building - Buildings designed to be environmentally responsible and resource-efficient. It’s about using less energy and sustainable materials while improving indoor comfort (like reducing noise!). - More about this concept in the article "🏗️ Building a Greener Future: Exploring the Driving Forces Behind China's Low-Carbon Construction Revolution".
Source: Ciaburro, G.; Puyana-Romero, V. Sustainable Membrane-Based Acoustic Metamaterials Using Cork and Honeycomb Structures: Experimental and Numerical Characterization. Buildings 2025, 15, 2763. https://doi.org/10.3390/buildings15152763
