Alternative methods to generate a first-order directional microphone

Abstract

This thesis deals with the implementation and analysis of diferent methods to generate a first-order directional microphone for source location and noise measurement purposes. The methods analysed include a cardioid capsule, and virtual methods such the combination of the signals of two omnidirectional microphones, the combination of the signals of an omnidirectional and a figure of 8 microphones, as well as a Soundfield microphone which is based on the Ambisonics principle. The frequency response function, directivity error and signal-to-noise ratio of the resulting first-order directional microphones have been experimentally studied by implementing each of the methods, performing measurements in the anechoic chamber of the Acoustics Group at NTNU and post-processing the obtained signals using MatLab. The results obtained from the experiments conclude that the optimum method to generate a first-order directional microphone for measurement purposes at the frequency range of interest of this project (from 80 Hz to 4 kHz) is to use an array of three omnidirectional microphones and combine their signals.