Abstract
Abstract. Plane wave actuators without an enclosure per se have a forward and backward radiation. The backward radiation is unwanted in many applications when a single direction radiation is desired. To avoid the disadvantages of an enclosure a system is proposed, which provides a high suppression of the unwanted backward radiation using a pair of plane wave actuators. This is achieved by adapted input signal filters. The influences of the second plane wave actuator to the forward radiated signal are suppressed as well. Additionally, the system also provides for- and backward radiation of different signals with a high suppression of the radiation directions crosstalk. The required power for the signal suppression depends on the physical damping of the plane wave actuators and the space in between. The first realized prototype is designed for flat panel dipole loudspeakers to deal with the mentioned problems in the acoustic domain. The filter design and a calibration algorithm for any given pairs of dipole loudspeaker are explained. The good performance of the developed system is proven by measurement results with the prototype system.
Highlights
Directed radiation is wanted in many applications to lower the effect of interference or to concentrate the radiated intensity to the target area
The first realized prototype is designed for electrostatic flat panel dipole loudspeakers to deal with the mentioned problems in the acoustic domain
This paper presents alternative approaches to achieve a one sided radiation, describes the theory of the developed novel approach, demonstrates a practical realization and shows the results achieved with a DSP-based prototype
Summary
Different approaches to suppress acoustical or electromagnetic traveling waves are available. A 180◦ phase delay and an additional delay according to the panel distance cancels out one radiation direction (Olson, 1973) This approach only grants the suppression of the backward radiation but does not take the influences on the forward radiation into account. Once the subsystems are described and determined it is possible to compute the desired filter transfer functions as well as the filter impulse responses in time domain (Corbach et al, 2009). The impulse response hr1(n) (Fig. 2b) describes all influences to the input The system is divided into subsystems according to the ac- signal x(n) radiated by the same loudspeaker and the output tive panel s ∈ {1,2} controlled by the discrete input signal x(n) and the occurring discrete output signal ysk(n) at a refsignal yr1(n) is observed on the opposite side of the double dipole. The high directivity and the low distance between the panels enlarge the area of controlled radiation nearly to the full sphere
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