A Study of the Relationship between Head Related Transfer Functions and Elevations

Head Related Transfer Functions (HRTFs) are signal processing models that represent the transformations undergone by acoustic signals, as they travel from their source to the listener’s eardrums. The study of HRTFs is a rapidly growing area with potential uses in virtual environments, auditory displays, the entertainment industry, human-computer interface for the visually impaired, aircraft warning systems, etc. The positioning of the sound source plays a major role in the resonant frequency of the HRTFs. In this paper, we examine the effect of changing the elevations of these sources; we examine the effect on the first peak and the first notch of HRTFs. We use the HRTF database at FIU DSP lab. This database hosts the HRTFs from 15 subjects and their 3-D images of conchas. For each subject, the database contains the Head Related Impulse Responses (HRIRs) for the sound sources placed at six elevations (54°, 36°, 18°, 0°, -18° and -36°) and twelve azimuths (180°, 150°, 120°, 90°, 60°, 30°, 0°, -30°, -60°, -90°, -120° and -150°). A relationship between the first peak or notch and the elevation can help us model HRTFs mathematically. This can reduce the size of a HRTF database and can increase the speed of HRTF related computations

The creation of a binaural spatialization tool

The main focus of the research presented within this thesis is, as the title suggests, binaural spatialization. Binaural technology and, especially, the binaural recording technique are not particu-larly recent. Nevertheless, the interest in this technology has lately become substantial due to the increase in the calculation power of personal computers, which started to allow the complete and accurate real-time simulation of three-dimensional sound-fields over headphones. The goals of this body of research have been determined in order to provide elements of novelty and of contribution to the state of the art in the field of binaural spatialization. A brief summary of these is found in the following list: • The development and implementation of a binaural spatialization technique with Distance Simulation, based on the individual simulation of the distance cues and Binaural Reverb, in turn based on the weighted mix between the signals convolved with the different HRIR and BRIR sets; • The development and implementation of a characterization process for modifying a BRIR set in order to simulate different environments with different characteristics in terms of frequency response and reverb time; • The creation of a real-time and offline binaural spatialization application, imple-menting the techniques cited in the previous points, and including a set of multichannel(and Ambisonics)-to-binaural conversion tools. • The performance of a perceptual evaluation stage to verify the effectiveness, realism, and quality of the techniques developed, and • The application and use of the developed tools within both scientific and artistic “case studies”. In the following chapters, sections, and subsections, the research performed between January 2006 and March 2010 will be described, outlining the different stages before, during, and after the development of the software platform, analysing the results of the perceptual evaluations and drawing conclusions that could, in the future, be considered the starting point for new and innovative research projects

Backward Compatible Spatialized Teleconferencing based on Squeezed Recordings

Commercial teleconferencing systems currently available, although offering sophisticated video stimulus of the remote participants, commonly employ only mono or stereo audio playback for the user. However, in teleconferencing applications where there are multiple participants at multiple sites, spatializing the audio reproduced at each site (using headphones or loudspeakers) to assist listeners to distinguish between participating speakers can significantly improve the meeting experience (Baldis, 2001; Evans et al., 2000; Ward & Elko 1999; Kilgore et al., 2003; Wrigley et al., 2009; James & Hawksford, 2008). An example is Vocal Village (Kilgore et al., 2003), which uses online avatars to co-locate remote participants over the Internet in virtual space with audio spatialized over headphones (Kilgore, et al., 2003). This system adds speaker location cues to monaural speech to create a user manipulable soundfield that matches the avatar’s position in the virtual space. Giving participants the freedom to manipulate the acoustic location of other participants in the rendered sound scene that they experience has been shown to provide for improved multitasking performance (Wrigley et al., 2009). A system for multiparty teleconferencing requires firstly a stage for recording speech from multiple participants at each site. These signals then need to be compressed to allow for efficient transmission of the spatial speech. One approach is to utilise close-talking microphones to record each participant (e.g. lapel microphones), and then encode each speech signal separately prior to transmission (James & Hawksford, 2008). Alternatively, for increased flexibility, a microphone array located at a central point on, say, a meeting table can be used to generate a multichannel recording of the meeting speech A microphone array approach is adopted in this work and allows for processing of the recordings to identify relative spatial locations of the sources as well as multichannel speech enhancement techniques to improve the quality of recordings in noisy environments. For efficient transmission of the recorded signals, the approach also requires a multichannel compression technique suitable to spatially recorded speech signals

Proceedings of the EAA Spatial Audio Signal Processing symposium: SASP 2019

International audienc

Virtual Heritage: Audio design for immersive virtual environments using researched spatializers.

This thesis work is based on a Virtual Heritage project being developed by the Systems of Representation research group. The objective of the project is to create a showcase demonstration on how the virtual reality (VR) could be used as an application for tourism in the heritage sector. In this context, my task was to develop a concept and prototype of how 'spatialized' sound could be used in a VR application. The initial location chosen for the concept was the ancient heritage burial site of Sammallahdenmäki, one of the Finnish heritage sites listed in the UNESCO register of World Heritage Sites. The thesis, that is written from an audio designer's perspective, focuses on three aspects of this project. First is the sound design for the Virtual Heritage project and the second is the quality of currently available 'spatializer' plug-ins used for headphone listening. In order to evaluate the process of designing 3D audio for virtual environments, the methods and principles within binaural rendering, sound design and immersion must be understood. Therefore, functions and theories within audio spatialization and 3D audio design are reviewed. Audio designers working on virtual reality content need the best possible solutions for creating believable 3D audio experiences. However, while working on the Virtual Heritage project, we did not find any comparative studies made about commercially available spatializer plug-ins for Unity. Thus, it was unknown what plug-in would have been the best possible solution for 3D audio spatialization. Consequently, two tests were conducted during this thesis work. First was an online test measuring which spatializer would be the most highly rated, in terms of perceived directional precision when utilizing head-related transfer functions without reverb or room simulations. The second was a comparative test studying if a spatialized audio rendering would increase immersion compared to non-spatialized audio rendering, when tested with the Virtual Heritage demonstration. The central aim in the showcase demonstration was to create an immersive virtual environment where users would feel as if they were travelling from the present, back to the Bronze Age, in order to understand and learn about the location’s unique history via auditory storytelling. The project was implemented utilising the Unity game engine. The research on music and other sound content used in the project’s sonic environment is explained. Finally, results of the project work are discussed.Tämä opinnäytetyö perustuu Virtual Heritage projektityöhön, joka on tehty Systems of Representation tutkimusryhmälle. Projektin tavoite on luoda malliesimerkki siitä, miten virtuaalitodellisuutta voitaisiin käyttää hyväksi turismisovelluksissa. Esimerkkikohteeksi projektille oli valittu Sammallahdenmäen hautaröykkiöt, joka on hyväksytty mukaan UNESCON maailmanperintöluetteloon. Tehtäväni oli toteuttaa Unity pelimoottorilla prototyyppi, jossa kartoitetaan virtuaalisen tilaäänen käyttömahdollisuuksia kyseisen teeman ympärillä. Opinnäyte on kirjoitettu äänisuunnittelijan näkökulmasta keskittyen kolmeen projektityöhön liittyvään keskeiseen osaan: prototyypin äänisuunnitteluun, immersion käsitteeseen sekä spatialisointi liitännäisten (plug-in) toimintaan ja laatuun. Virtuaalitodellisuuksiin sisältöä tuottavana äänisuunnittelijana tarvitsin parhaat mahdolliset työkalut uskottavan 3D äänimaailman luomiseen. Virtual Heritage projektia työstettäessä kävi kuitenkin ilmi, että ajankohtaista vertailevaa tutkimusta spatialisointi liitännäisten laatueroista ei ollut löydettävissä. Oli mahdotonta määritellä yksilöllisesti, mikä liitännäisistä on toimivin ratkaisu suurimmalle käyttäjäkunnalle. Täten oli tarpeellista toteuttaa kaksi tutkimusta. Ensimmäinen oli empiirinen verkkotutkimus, jolla arvioitiin spatialisointi liitännäisten suorituskykyä, kun mitataan subjektiivisesti äänen tilallisen sijoittumisen tarkkuutta kuulokekuuntelussa ilman kaikuprosessointeja. Tutkimuksessa parhaiten suoriutunut liitännäinen implementoitiin prototyyppiin. Toisessa kokeessa tutkittiin kuinka paljon implementoidun spatialisointi liitännäisen käyttäminen lisää virtuaalitodellisuuden immersiota verrattaessa spatialisoimattomaan ääneen, kun testialustana toimii Virtual Heritage prototyyppi. Projektin keskeisin tavoite oli luoda immersiivinen virtuaalitodellisuus, jossa käyttäjä voi kokea matkaavansa nykyajasta pronssikautiselle Sammallahdenmäelle ja oppia tällä tavoin kohteen ainutlaatuisesta historiasta äänikerronnan keinoin. Opinnäytetyössä esitellään äänikerronnan sisältöön ja toteutustapaan johtavat tutkimukset, tuotanto sekä ajatukset lopputuloksesta

Using Sonic Enhancement to Augment Non-Visual Tabular Navigation

More information is now readily available to computer users than at any time in human history; however, much of this information is often inaccessible to people with blindness or low-vision, for whom information must be presented non-visually. Currently, screen readers are able to verbalize on-screen text using text-to-speech (TTS) synthesis; however, much of this vocalization is inadequate for browsing the Internet. An auditory interface that incorporates auditory-spatial orientation was created and tested. For information that can be structured as a two-dimensional table, links can be semantically grouped as cells in a row within an auditory table, which provides a consistent structure for auditory navigation. An auditory display prototype was tested. Sixteen legally blind subjects participated in this research study. Results demonstrated that stereo panning was an effective technique for audio-spatially orienting non-visual navigation in a five-row, six-column HTML table as compared to a centered, stationary synthesized voice. These results were based on measuring the time- to-target (TTT), or the amount of time elapsed from the first prompting to the selection of each tabular link. Preliminary analysis of the TTT values recorded during the experiment showed that the populations did not conform to the ANOVA requirements of normality and equality of variances. Therefore, the data were transformed using the natural logarithm. The repeated-measures two-factor ANOVA results show that the logarithmically-transformed TTTs were significantly affected by the tonal variation method, F(1,15) = 6.194, p= 0.025. Similarly, the results show that the logarithmically transformed TTTs were marginally affected by the stereo spatialization method, F(1,15) = 4.240, p=0.057. The results show that the logarithmically transformed TTTs were not significantly affected by the interaction of both methods, F(1,15) = 1.381, p=0.258. These results suggest that some confusion may be caused in the subject when employing both of these methods simultaneously. The significant effect of tonal variation indicates that the effect is actually increasing the average TTT. In other words, the presence of preceding tones increases task completion time on average. The marginally-significant effect of stereo spatialization decreases the average log(TTT) from 2.405 to 2.264

Sensory Communication

Contains table of contents for Section 2 and reports on five research projects.National Institutes of Health Contract 2 R01 DC00117National Institutes of Health Contract 1 R01 DC02032National Institutes of Health Contract 2 P01 DC00361National Institutes of Health Contract N01 DC22402National Institutes of Health Grant R01-DC001001National Institutes of Health Grant R01-DC00270National Institutes of Health Grant 5 R01 DC00126National Institutes of Health Grant R29-DC00625U.S. Navy - Office of Naval Research Grant N00014-88-K-0604U.S. Navy - Office of Naval Research Grant N00014-91-J-1454U.S. Navy - Office of Naval Research Grant N00014-92-J-1814U.S. Navy - Naval Air Warfare Center Training Systems Division Contract N61339-94-C-0087U.S. Navy - Naval Air Warfare Center Training System Division Contract N61339-93-C-0055U.S. Navy - Office of Naval Research Grant N00014-93-1-1198National Aeronautics and Space Administration/Ames Research Center Grant NCC 2-77

Sonic interactions in virtual environments

This book tackles the design of 3D spatial interactions in an audio-centered and audio-first perspective, providing the fundamental notions related to the creation and evaluation of immersive sonic experiences. The key elements that enhance the sensation of place in a virtual environment (VE) are: Immersive audio: the computational aspects of the acoustical-space properties of Virutal Reality (VR) technologies Sonic interaction: the human-computer interplay through auditory feedback in VE VR systems: naturally support multimodal integration, impacting different application domains Sonic Interactions in Virtual Environments will feature state-of-the-art research on real-time auralization, sonic interaction design in VR, quality of the experience in multimodal scenarios, and applications. Contributors and editors include interdisciplinary experts from the fields of computer science, engineering, acoustics, psychology, design, humanities, and beyond. Their mission is to shape an emerging new field of study at the intersection of sonic interaction design and immersive media, embracing an archipelago of existing research spread in different audio communities and to increase among the VR communities, researchers, and practitioners, the awareness of the importance of sonic elements when designing immersive environments