Two problems that look identical and are not
Almost every disappointed acoustic panel customer made the same mistake: they bought absorption to solve a transmission problem. The two are physically different jobs.
- Reverberation - sound bouncing inside the room. Fixed with absorption.
- Transmission - sound passing through the wall, floor or ceiling to the next space. Fixed with mass, sealing and decoupling.
What absorption genuinely fixes
Put 15 to 25 percent of the room's surface area into PET felt panels and you can cut reverberation time dramatically. Speech becomes intelligible, phone calls stop echoing, and the room stops feeling loud even though the number of people in it has not changed. This is why open offices, restaurants and classrooms respond so well.
What absorption cannot do
A 9mm felt panel on a stud wall changes the transmission loss of that wall by a fraction of a decibel. The reason is the mass law: how much sound passes through a barrier depends overwhelmingly on how heavy the barrier is. Panels weigh 2 to 4 kg per square meter. A double layer of drywall weighs 20 to 30 kg per square meter. Absorption and insulation are stacked in series, and the panel is the thinner layer.
If you actually need isolation, work in this order
- Seal the air gaps. A 1mm gap around a door or a shared conduit can destroy the performance of an otherwise good wall.
- Add mass. A second layer of drywall, or mass-loaded vinyl where thickness is tight.
- Decouple. Resilient channels or a floating floor so vibration cannot bypass the mass.
- Treat the room with absorption last. Otherwise you reduce the echo, hear the same transmitted noise more clearly, and conclude the panels did nothing.
Specifying both layers correctly
Absorption is measured as NRC or SAA. Insulation is measured as STC for walls and IIC for floors. A wall can be STC 50 and the room still be unusable if the reverberation time is 1.8 seconds - and a room can be acoustically pleasant while every word still leaks to the corridor.
Rule of thumb for real projects
- Hotel guest room, apartment: insulation first, absorption second as decoration.
- Open office, restaurant, classroom: absorption first - transmission is rarely the complaint.
- Home studio or podcast room: absorption plus bass control; isolation only if neighbours complain.
- Gym or sports hall: absorption, because the noise source is inside the room and the room is enormous.
Tell us the problem you are trying to solve - echo inside the room, or noise coming through a wall - and we will tell you honestly which product does the job. Ask for a specification review.