Median Plane Localization - Psychoacoustics and Spatial Audio Effects

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School of Electrical Engineering | Doctoral thesis (article-based) | Defence date: 2024-05-31
Degree programme
65 + app. 73
Aalto University publication series DOCTORAL THESES, 109/2024
This thesis investigates the perception of the elevation of sources in the median plane by monaural spectral cues and, correspondingly, the synthesis of virtual source elevation using audio signal processing techniques. The contribution of spectral cues to median plane localisation was examined by measuring directional band effects with a more comprehensive approach than in existing literature. Additionally, the ability to segregate two concurrent sound sources in the median plane by spectral cues was examined with subjective listening tests, resulting in a measure of angular differentiation using monaural spectral cues alone. The measure was found to be finer than in an earlier study. The study also investigated the impact of added broadband noise on short sounds on localization in the median plane. The research revealed that, under specific circumstances, introducing background noise before a short sound burst can significantly improve localisation accuracy and mitigate inaccurate front-biased elevation perception in the median plane. A novel method for creating the perception of sound elevation was developed by utilising relative HRTF envelope filters. These filters were produced to examine the effectiveness of macroscopic HRTF envelopes that omitted the fine spectral details of pinna cues. The studies found that robust elevation perception can be achieved through the spectral features found in macroscopic HRTF envelopes as well as directional bands. Moreover, these spectral features were then utilised as the elevation filters by applying them to the early reflection part of stereo room impulse responses, which was subjectively verified to create the vertically extended perception of the reverberant sound field with acceptable colouration. The present thesis thus demonstrates that the macroscopic HRTF envelopes and directional cues can be widely beneficial across individuals diversely; however, individual-specific pinna-related features introduced in HRTFs enable more precise median plane localisation via spectral detail.
Supervising professor
Pulkki, Ville, Prof., Aalto University, Department of Information and Communications Engineering, Finland
spatial hearing, psychoacoustics, spatial audio
Other note
  • [Publication 1]: Taeho Kim, Henri Pontynen, Ville Pulkki. Vertical Direction Control Using Difference-Spectrum Filters in Stereophonic Loudspeaker Reproduction. Journal of the Audio Engineering Society, Volume 70, issue 3, pp 128-139, March 2022.
    DOI: 10.17743/jaes.2021.0055 View at publisher
  • [Publication 2]: Taeho Kim, Henri Pontynen. Perception of vertically separated sound sources in the median plane. In AES International Conference on Immersive and Interactive Audio, York, UK, March 2019.
  • [Publication 3]: Taeho Kim, Henri Pontynen, Ville Pulkki. Directional-band-dominant spectral region for the sound localisation in the median plane. In The 24th International Congress on Acoustics, Gyungju, South Korea, October 2022.
  • [Publication 4]: Taeho Kim, Ville Pulkki. Augmentation of perceived spatial extent of reverberation in stereophonic listening using elevation filters. In The 154th Audio Engineering Society Convention, Espoo, Helsinki, April 2023.
  • [Publication 5]: Taeho Kim, Ville Pulkki. Median plane localisation of short noise bursts in the presence of horizontally-spread white noise masker. Submitted to Journal of the Audio Engineering Society, Dec 2023.