Influence of listener's head in stereo reproduction using parametric loudspeakers

A parametric loudspeaker is known as a super directional loudspeaker by using nonlinear interaction between ultrasounds. The parametric loudspeaker is one of the prominent applications of nonlinear acoustics. The main applications have been limited to monaural reproduction. It is expected that a stereo reproduction using the parametric loudspeakers will lead to enjoy music and make a conversation without other persons' annoyance and trouble. So far, we conducted listening tests when the reproduced left and right signals had time difference. In using the parametric loudspeakers, listeners perceived sound localization in the correct direction. However, in using ordinary loudspeakers, they did not often perceive the sound localization in the correct direction. It was assumed that the directivity of the parametric loudspeaker was so sharp directional that the influence of crosstalk was reduced and the correct sound localization was perceived. In this report, inputs of the left and right ears are measured with a dummy head in reproduction using the parametric loudspeaker and ordinary loudspeaker. The measured inputs are analyzed and the influence of the head is clarified. The cross talk components, which are the sound from the left loudspeaker to the right ear and vice versa, are compared between both cases. The dependences of the directional angle are clarified. The causes of the difference of sound localization in stereo reproduction between using the parametric loudspeakers and using the ordinary loudspeakers are discussed.