VW PV 8223 Foams and Textile Absorbers - Acoustic Requirements and Measurement Methods

The standard "VW PV 8223 Foams and textile absorbers - Acoustic requirements and measurement methods," developed by Volkswagen, describes the acoustic requirements for foams and textile sound-absorbing materials and a test method for determining the absorption coefficient for incident sound, including evaluation and frequency scaling. This standard applies to vehicle components designed to absorb airborne noise. These components can include single-layer and multi-layer textile absorbers, foams, and molded foam parts.

As a general guideline, the acoustic requirements that apply are determined by the sound absorber material and the vehicle's comfort level requirements. The acoustics department determines this for the relevant component and material at the thickness specified in the drawing. The specifications apply to sample thicknesses between 6 mm and 25 mm. The measured absorption coefficients are converted to a 15 mm thickness by scaling the frequency values. Results for volumetric nonwoven fabrics are not to scale; the measured sound absorption coefficients are compared directly with the relevant specifications.

To measure the acoustic absorption coefficient of material samples or component samples made of textile absorbers or foam in incident sound, an impedance tube with a two-microphone method must be used in accordance with the standard "ISO 10534-2 Acoustics - Determination of acoustic properties in impedance tubes - Part 2: Two-microphone technique for normal sound absorption coefficient and normal surface impedance." The test setup in accordance with this standard specifies the impedance tube setup, including correction, and the measurement setup for the test. The standard and its correction also define the calibration of the two microphones and the entire measurement chain, including phase and amplitude mismatch.

The impedance tube geometry should be selected so that its operating frequency range covers at least 800 Hz to 6,4 kHz. If this is not possible with a single setup, several geometries can be used for measurement and the results compiled across the frequency range. If this method is used, the frequency ranges of the different geometries should overlap by at least one octave.

Both sides of the sample must be parallel and flat. Before measurement, the sample thickness must be determined according to EN ISO 9073-2. For volumetric nonwoven fabrics, the relevant measurement method C according to this standard should be used. Other materials should be measured according to methods A or B.

In contrast to the standard, at least four samples of the dimensions specified in EN ISO 9073-2 must be used for thickness measurement, and the sample size specified in the table must be cut to measure the sound absorption in the impedance tube. According to EN ISO 9073-2, four or more samples must be measured from each side to determine the thickness.

For all impedance tube samples prepared from test specimens, the thickness to be set on the impedance tube is the arithmetic average of all thickness measurements of the material or flat component. The impedance tube sample holder should be adjusted so that the distance from the measuring surface to the high-impedance backing plate matches the measured average sample thickness.

The sample should be placed in the impedance tube with its bottom surface flush with the high-impedance side of the tube. This prevents the formation of an air layer between the bottom surface of the sample and the high-impedance backing plate.

Samples made from materials that are easily compressible (e.g., meltblown nonwovens) may need to be slightly embossed before measurement. This will ensure that the top surface of the sample is flush with the measurement surface and that no air pockets form underneath. This will ensure that the measured sample thickness is accurately reproduced in the impedance tube.

During testing, after calibration, samples are placed in the measuring tube using appropriate sample holders. Testing is carried out according to EN ISO 10534-2, leaving no wall gaps. For this test, the maximum frequency resolution between measurement values ​​is 20 Hz. A sufficient number of averaging steps per measurement should be used to obtain a smooth curve of the sound absorption coefficient across frequencies and to minimize measurement errors. A frequency range of 8 Hz and 100 averaging steps is recommended. The number of samples per material or component depends on the material type and the size and geometry of the component. The table titled "Number of Impedance Tube Samples Depending on the Material" is used for this purpose.

The number of samples can be adjusted by agreement with the acoustics department. If a section does not have sufficient sampling area, the required number of samples can be obtained by using multiple sections.

To make materials of different thicknesses comparable, the frequency values ​​of each measurement must be scaled to correspond to a standard thickness of 15 mm.

The VW PV 8223 standard is compliant with the EN ISO 10534-2 standard , an international standard focusing on the same acoustic testing methodology . In short, this standard describes how to measure how well certain vehicle materials absorb sound. It is designed to help evaluate the acoustic performance of materials such as foams and textile absorbers used in vehicle interiors.

This standard is part of a broader set of test methods implemented by the Volkswagen Group covering various aspects of material performance (e.g., environmental durability, fading, emissions, abrasion). These standards ensure that materials meet rigorous quality and durability criteria before they are approved for use in VW vehicles.

The VW PV 8223 standard is considered important for the following reasons:

• Passenger comfort: Modern vehicles are expected to offer a quiet and refined cabin experience. Materials such as foam and textiles used must effectively absorb sound to reduce:
  • Road noise
  • Engine and drivetrain noises
  • Wind and vibration noise

By testing materials to this standard, VW ensures that only those with good sound absorption properties are used in production.

• Consistent quality control: This standard provides a standardized method for testing sound absorption based on EN ISO 10534-2 using the transfer function method in an impedance tube. This ensures:
  • All materials are tested under the same conditions
  • Data are repeatable and comparable
  • VW suppliers follow the same quality criteria
• Regulatory and brand expectations: Volkswagen aims to meet:
  • Regulatory acoustic standards (especially in markets with noise restrictions)
  • Consumers' expectations for a quiet cabin, especially in electric vehicles where engine noise is minimal and other noises are more pronounced
• Design optimization: Using test results against this standard, designers can:
  • You can choose the most effective materials for different parts of the cabin.
  • Minimize overall vehicle weight by choosing the most efficient acoustic materials (important for fuel efficiency and electric vehicle range)
  • Can balance cost and performance during material procurement
• Supplier harmonization: Ensures suppliers and VW designers speak the same technical language. Any recommended materials:
  • Must pass this test
  • Provide data in a format that the VW Group can trust
  • Must meet or exceed minimum acoustic performance levels

Our organization, which has been operating for many years and meticulously follows global developments in science and technology, employs a team of experienced professionals and a broad infrastructure to conduct testing, measurement, and analysis in a wide range of areas for businesses across all sectors. In this context, we also provide testing services in accordance with the "VW PV 8223 Foams and Textile Absorbers - Acoustic Requirements and Measurement Methods" standard.