Branko Somek

Acoustic echo cancellation in mobile radio by adaptive Legendre filtering

Discrete-time analysis and modeling of resonant and reverberant systems has many applications in acoustics. Although autoregressive moving average modeling, which yields a pole-zero filter has a lot of modeling power, Pronys and Steiglitz-McBride estimation methods can result in an unstable model, even for stable target systems. On the other hand, finite impulse response modeling can require a large filter order in order to accurately model the target system. This paper discusses the application of an adaptive Legendre network realization on the acoustic echo cancellation in mobile radio. Such kind of system modeling has an infinite impulse response, but with all the poles inside the unit circle.

The high‐power acoustical warning systems

The high‐power acoustical warning and informing systems are necessary for various aims. Mostly these systems work in open space, particularly in urban areas (towns, villages, river valleys). The useful coverage depends upon used transducers‐emitters and installed electrical power. Almost all such systems have omnidirectional coverage, i.e., equal acoustical energy is radiated in all directions. The environmental conditions (air temperature and humidity, strength and direction of wind, etc.) and miscellaneous barriers (buildings, land configuration, trees) have an influence on the sound propagation for warning and informing systems. The other important point is that these systems are also used for spoken messages, not only for alarm. The computer simulation was done which takes all these parameters into account, and enables calculation of needed acoustical and electrical parameters.