Compensation of speaker directivity in speech recognition using HMM composition

In hands-free speech recognition the speaker should be able to move freely in front of the speech acquisition device. However, the speech signal is then submitted to variations due to the continuous change of position in the acoustic space. This paper focuses on the role of speaker head rotations as compared with static situations in anechoic conditions. The effect of speaker directivity in speech recognition performance degradation is demonstrated and a compensation method based on HMM composition is proposed to increase the performance