2D to 3D ambience upmixing based on perceptual band allocation

3D multichannel audio systems employ additional elevated loudspeakers in order to provide listeners with a vertical dimension to their auditory experience. Listening tests were conducted to evaluate the feasibility of a novel vertical upmixing technique called “perceptual band allocation (PBA),” which is based on a psychoacoustic principle of vertical sound localization, the “pitch height” effect. The practical feasibility of the method was investigated using 4-channel ambience signals recorded in a reverberant concert hall using the Hamasaki-Square microphone technique. Results showed that the PBA-upmixed 3D stimuli were significantly stronger than or similar to 9-channel 3D stimuli in 3D listener-envelopment (LEV), depending on the sound source and the crossover frequency of PBA. They also significantly produced greater 3D LEV than the 7-channel 3D stimuli. For the preference tests, the PBA stimuli were significantly preferred over the original 9-channel stimuli

Psychoacoustic Considerations in Surround Sound with Height

This paper presents recent research findings in the psychoacoustics of 3D multichannel sound recording and rendering. The addition of height channels in new reproduction formats such as Auro-3D, Dolby Atmos and 22.2, etc. enhances the perceived spatial impression in reproduction. To achieve optimal acoustic recording and signal processing for such formats, it is first important to understand the fundamental principles of how we perceive sounds reproduced from vertically oriented stereophonic loudspeakers. Recent studies by the authors in this field provide insights into how such principles can be applied for practical 3D recording and upmixing. Topics that are discussed in this paper include the interchannel level and time difference relationships in terms of vertically induced interchannel crosstalk, the effectiveness of the precedence effect in the vertical plane, the aspect of tonal coloration resulting from vertical stereophonic reproduction, the effect of vertical microphone spacing on envelopment, the effect of interchannel decorrelation, and the use of spectral cues for extending vertical image spread

Investigation on the Phantom Image Elevation Effect

Listening tests have been carried out in order to evaluate the phantom image elevation effect depending on horizontal stereophonic base angle. Seven ecologically valid sound sources as well as four noise sources were tested. Subjects judged the perceived image positions of phantom centre image created with seven loudspeaker base angles. Results generally showed that perceived images were elevated from front to above as the loudspeaker base angle increased up to around 180°. This tendency depended on the spectral characteristics of sound source. The perceived results are explained from both physical and cognitive points of view

The Effect of Interchannel Time Difference on Localisation in Vertical Stereophony

Listening tests were conducted in order to analyse the localisation of band-limited stimuli in vertical stereophony. The test stimuli were seven octave bands of pink noise, with centre frequencies ranging from 125–8000Hz, as well as broadband pink noise. Stimuli were presented from vertically arranged loudspeakers either monophonically or as vertical phantom images, created with the upper loudspeaker delayed with respect to the lower by 0, 0.5, 1, 5 and 10ms (i.e. interchannel time difference). The experimental data obtained showed that localisation under the aforementioned conditions is generally governed by the so-called “pitch-height” effect, with the high frequency stimuli generally being localised significantly higher than the low frequency stimuli for all conditions. The effect of interchannel time difference was found to be significant on localisation judgments for both the 1000-4000Hz octave bands and the broadband pink noise; it is suggested that this was related to the effects of comb filtering. Additionally, no evidence could be found to support the existence of the precedence effect in vertical stereophony

Virtual Audio - Three-Dimensional Audio in Virtual Environments

Three-dimensional interactive audio has a variety ofpotential uses in human-machine interfaces. After lagging seriously behind the visual components, the importance of sound is now becoming increas-ingly accepted. This paper mainly discusses background and techniques to implement three-dimensional audio in computer interfaces. A case study of a system for three-dimensional audio, implemented by the author, is described in great detail. The audio system was moreover integrated with a virtual reality system and conclusions on user tests and use of the audio system is presented along with proposals for future work at the end of the paper. The thesis begins with a definition of three-dimensional audio and a survey on the human auditory system to give the reader the needed knowledge of what three-dimensional audio is and how human auditory perception works

Evaluation of the Phantom Image Effect for Phantom Images

This paper introduces the author’s recent research on the elevation effect perceived with horizontal phantom images. Early research in stereophony suggests that a phantom centre image produced by two loudspeakers symmetrically placed from the listener position would be perceived in an elevated position, with its elevation angle increases as the loudspeaker base angle increases. In particular, an image presented from loudspeakers placed around the listener’s sides would be perceived overhead. With 3D audio formats employing height and overhead channels in mind, the aforementioned elevation effect is considered to be useful for creating a virtual overhead loudspeaker image, especially for sound effects using just ear-level loudspeakers (e.g. in downmix scenarios). Another important psychoacoustic principle relevant to 3D audio formats is the so- called ‘pitch-height’ effect, which suggests that the higher the frequency of a sound is the higher its image will be perceived. However, past research in this topic only considered loudspeakers placed in the median plane. From the above background, several subjective experiments have been conducted on the elevation of horizontally oriented phantom image. This paper first presents a vertical localisation test conducted with frontal stereo loudspeakers using octave-band noise stimuli. The results not only confirm the elevation effect for broadband noise, but also show the existence of an elevation effect for middle frequency bands. The second experiment introduced in this paper verifies the existence of the virtual overhead perception depending on loudspeaker base angle but also shows the effect heavily depends on the type of sound source

Surround by Sound: A Review of Spatial Audio Recording and Reproduction

In this article, a systematic overview of various recording and reproduction techniques for spatial audio is presented. While binaural recording and rendering is designed to resemble the human two-ear auditory system and reproduce sounds specifically for a listener’s two ears, soundfield recording and reproduction using a large number of microphones and loudspeakers replicate an acoustic scene within a region. These two fundamentally different types of techniques are discussed in the paper. A recent popular area, multi-zone reproduction, is also briefly reviewed in the paper. The paper is concluded with a discussion of the current state of the field and open problemsThe authors acknowledge National Natural Science Foundation of China (NSFC) No. 61671380 and Australian Research Council Discovery Scheme DE 150100363