Acoustic fabric and standards: acoustic performance

Which standards and certifications provide meaningful insight into the quality, practical usability, and performance of a speaker fabric? Our blog series “Acoustic fabric and standards” offers a step-by-step overview of the key standards, their practical relevance, and the defining parameters for these technical textiles. We begin with the most decisive aspect: acoustic transparency.

 

How is the acoustic performance of speaker fabric measured?

One of the main challenges when seriously evaluating acoustic and speaker fabrics lies in the wide range of technical standards that are often cited without proper context. The majority of these standards originate from building acoustics and focus on sound absorption. As a result, they are only of very limited relevance when applied to acoustically transparent textiles.
 

Missing the point: standards focused on sound absorption

A classic example is EN ISO 10534-2. This standard describes how the sound absorption coefficient of a material is measured in an impedance tube. It determines how effectively a material converts sound energy into heat, thereby reducing sound transmission. This is highly useful for assessing sound-absorbing materials such as acoustic foam, heavy wall coverings, or room absorbers, but largely irrelevant when it comes to acoustically transparent fabrics.

After all, acoustic cloth is designed to do the exact opposite of an insulating material. It should allow sound to pass through with minimal alteration, meaning it should absorb as little sound as possible. The measured absorption coefficient α, which indicates how much sound a material absorbs, will be very low by design. A measurement according to EN ISO 10534-2 may confirm that the fabric absorbs little sound, but it offers no insight into its frequency behaviour, which is essential when assessing suitability as a speaker cloth.

Similarly, values such as Rw (weighted sound reduction index), which describes how well a material reduces sound transmission between rooms, or DnT,w, which normalises sound insulation based on room acoustics and reverberation time, provide little meaningful information in this context. At best, they confirm that a fabric absorbs very little sound, but this is a basic requirement for sound-transparent textiles rather than a distinguishing feature.
 

Which indicators reflect sound permeability?

More relevant are parameters that provide insight into sound transmission and frequency response neutrality. These include:
Air permeability according to ISO 9237: Measurements based on this standard describe how much air passes through a fabric sample, expressed in litres per square metre per second. This provides a strong indirect indicator of acoustic transparency. Since sound travels through air, air permeability correlates closely with acoustic performance. The higher the airflow at a given pressure of 1 bar, the lower the acoustic resistance. High-quality speaker fabrics from Akustikstoff.com achieve air permeability values well above 8,000 l/m²/s. In practice, this means that frequency response and tonal balance remain unchanged.

Transmission loss: This parameter describes how much sound energy is lost when passing through a material. One relevant method is ASTM E2611-09, which determines normal incidence sound transmission using a transfer matrix approach, effectively measuring how much sound energy is lost during direct transmission. While technically precise, this method is complex and primarily of interest to specialists.

Fortunately, transmission loss can also be assessed more simply by measuring how sound pressure level and frequency response change when a sweep signal passes through a fabric compared to a reference measurement without the material. A common method is to measure the sound pressure level (SPL) in decibels (dB SPL). The result is a detailed curve showing variations in sound pressure across the entire frequency spectrum.

For our fabrics, such measurements have been carried out by internationally recognised acoustician and studio designer Dennis Busch (Acoustic Spaces). You can find the results for each fabric in the product specifications under “Acoustic measurements”.

This was the first part of our series on navigating standards for speaker fabrics. In the next article, we will explore which testing parameters and standards provide meaningful insight into the practical workability of these materials.