Perceptual Measurement And Research In The Effect Of Interaural Time And Level Differences To The Acoustic Localization

With rapid development of computer technology and increasing demand of quality of life,consumers have been paying increasingly attention to the application of three dimensions(3D)technology in the video and audio,which promotes audio technology develop rapidly.From mono and double channels to 3D stereo,studies have been succeed in the better surround and spatial effects on the audio.In the audio signal,however,the amount of data have been increasing with the raising of number of channels as getting better effects,so that it brings enormous pressure to the storage capacity and transmission bandwidth.Therefore,an efficient method by which digital audio data could be encoded and transmitted with a much lower bit rate is needed.In order to effectively compress multi-channel audio,coding technique of Binaural Cue Coding(BBC)can be used to process these multi-channel signals to get a single of downmixed channel and information of binaural cues.The single of downmixed audio channel consisted of all input audio channels,which can be transmitted after encoding and the information of binaural cues including Interaural Time Difference(ITD),Interaural Level Difference(ILD)and Interaural Coefficient(IC)indicating the direction of sound sources in audio signals,which will be encoded to side information to transmit.After getting transmission of the data,the receiver can decode downmixed channel and side information to restore the original multi-channel signals.Because the bate of side information is lower than the mono audio signal,the technology of BBC can be used to get a high quality of multi-channel audio signals with less transmitting data.However,the perception of human auditory system is limited for the ITD and ILD,side information can be efficiently quantified and encoded only when the threshold of interaural cues are measured.Although researchers have tested perceptual characteristic of interaural cues on many of positions and frequencies so far,the threshold of each interaural cue is tested in isolation.In reality,however,ITD and ILD can be existed simultaneously on sound location,so it is difficult to evaluate and establish the relative contribution of ITD and ILD to localizing sound when only one perceptual characteristic of interaural cue is tested.In the paper,Just Noticeable Difference(JND)of ITD and ILD will be measured simultaneously,and then the experimental results are analyzed to get the impacts of these two interaural cues on the sound location,which could provide more efficient coding technique with theoretical basis.Therefore,the primary work of this thesis includes the following parts:1.Improving a testing system based on psychological methods so that the testing system can be used in measuring the perceptual characteristic of two interaural cues.2.Subjects are allowed to measure Just Noticeable Difference of ITD and ILD in many frequencies and positions in order to get a complete result of interaural cues on sound location.Then,some conclusions for the relative contribution of interaural time and level differences to the sound localization could be reached based on the complete result.3.Comparing the result of two interaural cues in this experiment with the threshold of one interaural cue in previous testing and then analyzing the differences and similarities between two interaural cues and one interaural cue on the sound location.4.The surface fitting of JND will be obtain through interpolation method and a more accurate three dimensional surface model of position-frequency-JND could be got.Then,some appropriate conclusions can be reached according to the surface model.