Dynamic Virtual Auditory Display Based On Android Phone

Virtual Reality(VR)provides immersive experience for users.Deriving from static virtual auditory display,dynamic virtual auditory display(DVAD)includes the dynamic cue in binaural rendering so as to effectively reduce front-back and up-down confusion in reproduction.DVAD reconstructs the spatial information of sound,provides a more natural and realistic hearing experience.And it is an ideal technique to realize the immersion experience required by VR.Since the 90 s of last century,international and domestic research groups have developed some DVAD systems for purpose of scientific researches.However,there is little chance to promote these systems to the civilian market,as the systems are too expensive and complex.With the improvement of hardware performance and optimization of software algorithms,the mobile phone can afford the basic computation cost of VR and achieve the simple effect of virtual auditory reproduction.In June 2016,Google VR SDK was released by Google,successfully implementing virtual Ambisonics technology in the mobile phone to achieve DVAD.This tool reduces the difficulty of DVAD on the mobile phone,and promotes the development of virtual auditory technology.Based on this status,some following studies are carried out.Firstly,in order to reduce the effective length of Head-Related Impulse Response(HRIR),the minimum phase approximation of HRIR is used.The minimum phase HRIR is reduced by principal component analysis(PCA).Then the bilinear interpolation of PCA weights and the ineraural time difference(ITD)based on spherical harmonic is used.Therefore,the data for full space HRIR is compressed.Secondly,a basic virtual auditory reproduction system is implemented on an android phone including several functional modules.The foundation module of the system is based on the Google VR SDK.In the head tracking module,the system can track the listener's head movement in real time with the application of fusion data from acceleration sensor,electronic compass and gyroscope using complementary filter.In signal processing parameter calculation module,PCA weight and ITD are interpolated in real time,according to the direction of the virtual sound source.In signal processing module,liner delay of signal is compensated,according to ITD.And a PCA-based HRIRs binaural synthesis procedure is used.This procedure can reduce the computation cost and avoid the audible artifacts.Scenarios update rate,system latency time and the maximum number of virtual sound sources supported by the system are tested.The results indicate that the system can meet the basic need of dynamic reproduction.Then the factors that affect the system latency time are analyzed on the perspective of the android system sound playback delay,.Finally,the developed system is used in binaural dynamic virtual auditory display of 22.2 channel surround sound.A virtual source localization experiment is carried out.The results of experiment show that with the dynamic reproduction system,most of front-back confusion and some up-down confusion in headphone presentation is reduced.In addition,the dynamic system is able to improve accuracy of localization.In a word,this work studies the VR sound technology based on Android phone,and provides the foundation for next practical application.