WellenFeld H 104: Simulation and Measurement
In order to predict the sound level distribution generated from the system in the room, a free-field simulation was calculated with the simulation software EASE 4.2, now extended to allow for the direct calculation of the individual speaker filter through a WFS operator. This calculation was performed on the basis of the loudspeaker directivity pattern (see Figure: Balloon-Representation), determined by a measurement in an anechoic half-room and for the individually configured equalization of the loudspeaker modules for six local spatial areas. The simulations of the the sound fields show a good compliance between the primary (virtual sound sources) and the secondary sources (LS-array).
- Abbildung : Simulation einer Punktschallquelle 4 m hinter dem LS-Array
- © privat
At the same time, the achievable direct sound
level in the room can be calculated on the basis of a maximum level of
the individual modules of 102 dB at 1 m distance, the directivity of
the loudspeakers and the required individual signals of all speakers
for the WFS.
To verify the correct functionality of hardware, software and network components, impulse responses of different virtual sound sources synthesized through the system at multiple receiver locations in the hall were recorded by a team from the TU-Delft. In this way, the influence of room reflections could be examined specifically, which were of course not completely suppressed through the implementation of the room acoustic requirements.
- Figure: Wave field of a centrally postioned, frontal point sound source in space-time-representation
- © TU Berlin
The figure shows the sound field of a central, frontal point sound source that was measured by a microphone array in the back of the room over a time range which includes all first order reflections. An evaluation of the sound level relations indicates a suppression of early reflections by more than 6 dB even in the (critical) rear part of the room, so that the influence of the room acoustics can be seen as non-critical (referring to the experience made with other WFS-systems).