Environmental Noise

Far Field Scan & Paint

ScananPaint Scheme CarFront LoudSpeakersAntiphase Click to enlarge

Making use of the Scanning method already developed for Scan and Paint application and combining this with the usage of a reference sensor, a virtual array, as big as needed and as spatially separated as needed can be simulated reducing costs dramatically, obtaining an adaptive resolution array, re-scalable and with such a flexibility range in frequency and space for locating and mapping stationary noise fields.

The measurement routine is based on determining and visualizing the properties of the sound field moving the probe slowly over a virtual measuring plane from which the interest area can be seen, recording the pressure and velocity as a video image is captured at the same time. For each time interval the video image is used to determine the location of the sensor so the measured pressure and particle velocity are referenced to an exact point so to a virtual sensor. As a reference sensor is maintained in a fixed position, the spatial phase information is kept, so the magnitude and phase variations across the space are calculated. Varying the scanning speed, the frame rate and the camera angle the frequency and spatial resolution between measurement points are modified. Each scanning position becomes then a virtual sensor having then unlimited spatial and frequency resolution configurations.

Once the noise sources are located by using only two sensors, the real emission, contribution and interaction on the listeners position is calculated by adding the  “Transfer Path Analysis” to the results, allowing to discern the real annoying noise sources and then the most efficient way to solve each particular case interrupting the transfer path between noise source and listener or the interaction between noise sources. To do so, two options are possible depending on the distance to the noise source and emplacement. For relatively close positions a monopole source is used in order to excite the transfer path and apply the reciprocal path from listener to source. For further positions where the monopole emitting level is not sufficient, the transfer path is simulated taking into account the geometry of the emplacement.

Features:

  • Broadbanded 20 to 20.000 Hz
  • Automatic synchronization of measurements with video recording
  • Direct measurement of pressure and particle velocity
  • Scalable spatial and frequency resolution
  • Unlimited virtual sensors with only two real
  • Transfer path analysis for emission, interaction and global level contribution of noise sources

 

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