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There are currently a number of measurement methods to characterize a road surface with regard to noise. This can be done by measuring the noise emission directly or indirectly via the parameters that are important for the noise emission.

Direct methods are:

  • Statistical Pass-by (SPB)
  • Close Proximity (CPX)

Indirect methods are:

  • texture
  • absorption

SPB method

The aim of the Statistical Pass-by (SPB) method is to accurately record the sound properties of a road surface for light, medium and heavy motor vehicles. The SPB measurement method is standardized in the international standard ISO 11819-1. The maximum noise level and vehicle speed of a large number of vehicles from existing traffic (approx. 100) are measured at a fixed position.

CPX method

The CPX method is designed to evaluate the homogeneity and temporal behavior of the acoustic properties of a road surface on different sections of a road surface. The CPX method is laid down in the provisional ISO standard 11819-2. Here, a trailer is driven over the road surface, while at the same time the speed and the noise level close to the tire / road surface of the standard measuring tires are measured.

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Texture measurements

The purpose of the texture measurement with the laser profilometer is to map the micro and macro texture of a road surface. The measuring method is laid down in the ISO standard 13473-1 / 2/3/4. With this measurement technique, a laser projects a beam of light at an angle on the road surface. A sensor captures the reflected light. The displacement of the light reflection on the sensor is a measure of the texture.

We have a 3D laser texture meter at our disposal.

Absorption measurements

in situ

The purpose of the in situ method is to determine the acoustic absorption of a screen on site in a fast, non-destructive manner. A sound wave is sent on the screen via a source. Due to the acoustic absorption, only a part of it will reflect. The absorption value is determined from the ratio between reflecting and incident sound.We have a Microflown system at our disposal.

Impedance tube method

The purpose of the absorption measurements with the Tube of Kunt is to determine the acoustic absorption of a sample. This method is laid down in ISO standard 10534-1 / 2. De Buis van Kunt is a laboratory instrument that can be used to determine the sound absorption of cores or test specimens produced in the lab.