Comparison of Two Methods for Measurement of Horn Input Impedance

Abstract

Two methods to measure the acoustic input impedance of a horn are compared. First method measures standing wave patterns in a tube which is loaded by the horn. The input impedance is calculated from the position of the first minimum in the standing wave pattern, and the ratio of maximum and minimum sound pressure level in the tube. Secondly we applied a direct method. A novel flow sensor, the microflown, is used together with a pressure microphone, which are mounted in the throat of the horn. Results from both measurements are compared with simulated models. 0 INTRODUCTION Horn loudspeakers are widely used in the area where one needs good --frequency independent-- directivity of sound, together with high sound pressure levels. Disadvantage of this type of loudspeaker is its production of excessive distortions at high driving levels. In preliminary research concerning compensation of this distortion, it appeared that the transfer characteristics of the horn itself need to be known accu...