Directivity of Human and Artificial Speech

Abstract

This paper is a study on howdirectivity characteristics of artificial mouths correspond to the directivity of a real speaker. The motivation for the research is the measurement methods that are applied in the telecommunication industry for the microphones of phones and their accessories. Responses of a mouth of an artificial torso simulator, B&K HATS 4128 were measured to several positions 1. The same measurements were repeated for a group of test subjects. The measurement positions corresponded to the same positions were the microphones of phones and their accessories, so called headsets, would lay. The basic mechanisms that produce the directivity pattern are discussed and also the contribution of the speech content is shown. The main contributor to the directivity is the mouth aperture size. The acoustical characteristics of the upper body are also a significant factor if the position is not directly in front of the mouth. More than 10 dB differences were found between HATS and an averaged test subject. The key finding is that HATS is too directional at high frequencies. To enhance the correspondence of the telephonometry to real speakers, a simple equalization scheme and two structural improvement proposals to HATS are introduced.