Why Does the Air Gap Matter When Installing Acoustic Felt?
For buyers sourcing Acoustic Felt for commercial buildings, offices, hotels, public spaces, and interior acoustic projects, most attention is usually given to material thickness, density, or sound absorption ratings. However, one equally important factor is often overlooked—the Air Gap.
In reality, the same Sound Absorbing Felt can perform differently when installed using different configurations, even if the material specifications remain exactly the same.
Therefore, before comparing different suppliers or acoustic test reports, buyers should confirm not only the material itself, but also whether the testing conditions include an Air Gap.
1. What Is an Air Gap in Acoustic Felt Installation?
An Air Gap is the air cavity between Acoustic Felt and a rigid wall or ceiling surface.
It is not another material, but a space created by the installation structure.
In architectural acoustic projects, Acoustic Felt may be installed directly against a wall, or it may be mounted using frames, suspension systems, or other installation methods that create an air cavity behind the material.
For buyers, the Air Gap is part of the installation configuration rather than the material specification, which is why it is often missing from RFQ documents.
2. Why Does an Air Gap Affect Sound Absorption?
The sound absorption performance of porous fiber materials depends not only on the material itself, but also on how sound waves interact with the surrounding air.
When an Acoustic Felt is installed with an Air Gap behind it, both the fiber structure and the air cavity participate in dissipating sound energy, often improving performance at certain mid and low frequencies. By comparison, direct wall installation relies more heavily on the material's own thickness and fiber structure.
This is why laboratory reports often specify conditions such as:
No Air Gap
20 mm Air Gap
50 mm Air Gap
200 mm Air Gap
Buyers should never compare two NRC or sound absorption values without confirming that they were tested under the same installation conditions.
3. Why Do Wall and Ceiling Installations Create Different Air Gaps?
Although both Wall Acoustic Insulation and Ceiling Acoustic Insulation use Acoustic Felt, their installation structures are often different.
Wall systems may use direct fixing or internal wall construction, while suspended ceilings naturally create different air cavity depths through framing or hanging systems.
As a result, the same Acoustic Felt should not be expected to deliver identical acoustic performance in both applications.
The correct comparison should focus on:
Installation Location
Installation Structure
Air Gap Depth
Test Configuration
rather than simply comparing material names.
4. Why Should Buyers Never Ignore the Air Gap in Acoustic Test Reports?
Many suppliers provide Sound Absorption Test Reports, but one of the most frequently overlooked details is the installation configuration used during testing.
For example, two reports may evaluate materials with the same thickness, yet one is tested without an Air Gap while the other includes an air cavity. These results should not be compared directly.
During sample evaluation, buyers should confirm:
Was an Air Gap included in the test?
What was the Air Gap dimension?
Was the tested thickness identical to the supplied sample?
Does the installation method match the actual building project?
Only when the testing configuration closely reflects the real project can the acoustic data become meaningful for purchasing decisions.
5. What Air Gap Information Should Be Included in an RFQ?
For architectural Acoustic Felt projects, buyers should include the following information when requesting a quotation:
Application: Wall or Ceiling
Installation Method: Direct, Suspended, or Composite Structure
Air Gap: Whether an air cavity is planned and its estimated depth
Required Thickness: Target thickness range
Target Acoustic Performance: Project acoustic objective
Fire Requirement: Any applicable building fire standard
Providing complete installation information allows the supplier to recommend a more suitable Acoustic Felt for Walls and Ceilings and provide acoustic data that matches the intended installation configuration.
For architectural acoustic projects, HuiZhou JinHaoCheng Nonwoven Co., Ltd. can provide acoustic nonwoven material solutions based on different wall, ceiling, and installation structures, with support for customized specifications and OEM / ODM production.
Conclusion
For Acoustic Felt, the Air Gap is not a minor installation detail—it is an important factor that influences both laboratory test results and real project performance.
Instead of comparing only thickness, density, or NRC values, buyers should also verify the Air Gap, installation method, and testing configuration before making a purchasing decision.
Only when the material specification matches the installation structure can Acoustic Felt achieve more reliable acoustic performance in architectural projects.
