Separation of forward and backward acoustic waves in a car exhaust by array processing

We present a new interdisciplinary application of digital signal processing and its results in comparison with the application of classical methods. The problem is the separation of two acoustic waves propagating along an exhaust pipe. It has been proved that the use of the array signal processing technique-signals are registered by an array of sensors placed along the pipe and processed by means of the LCMV beamformer-has achieved very good results under bad conditions such as uncertainty in the knowledge of the propagation speed. The array technique has also been applied to the separation of two pressure waves generated by the discharge of a fuel injection pump. In this case the results have been good but a preprocessing must be done due to the pulse characteristics of these pressure waveforms.