The theory of recording and reproduction of three-dimensional sound fields based on spherical harmonics is reviewed and extended. Free-field, sphere, and general recording arrays are reviewed, and the mode-matching and simple source approaches to sound reproduction in anechoic environments are discussed. Both methods avoid the need for both monopole and dipole loudspeakers—as required by the Kirchhoff–Helmholtz integral. An error analysis is presented and simulation examples are given. It is also shown that the theory can be extended to sound reproduction in reverberant environments.

/pdf/three-dimensional-surround-sound-systems-based-on-spherical-gts6rffrmw.pdf

Three-Dimensional Surround Sound Systems Based on Spherical Harmonics

Anyone who watches the television news has seen images of firefighters rescuing people from burning buildings and paramedics treating bombing victims. How do these individuals make the split-second decisions that save lives? Most studies of decision making, based on artificial tasks assigned in laboratory settings, view people as biased and unskilled. Gary Klein is one of the developers of the naturalistic decision-making approach, which views people as inherently skilled and experienced. Since 1985, Klein has conducted fieldwork to find out how people tackle challenges in difficult, nonroutine situations. Sources of Power is based on observations of humans acting under such real-life constraints as time pressure, high stakes, personal responsibility, and shifting conditions. In addition to providing information that can be used by professionals in management, psychology, engineering, and other fields, the book presents an overview of the research approach of naturalistic decision making and expands our knowledge of the strengths people bring to difficult tasks.

Sources of Power: How People Make Decisions

We conducted a mixed methods study of the use of the Meerkat and Periscope apps for live streaming video and audio broadcasts from a mobile device. We crowdsourced a task to describe the content, setting, and other characteristics of 767 live streams. We also interviewed 20 frequent streamers to explore their motivations and experiences. Together, the data provide a snapshot of early live streaming use practices. We found a diverse range of activities broadcast, which interviewees said were used to build their personal brand. They described live streaming as providing an authentic, unedited view into their lives. They liked how the interaction with viewers shaped the content of their stream. We found some evidence for multiple live streams from the same event, which represent an opportunity for multiple perspectives on events of shared public interest.

/pdf/meerkat-and-periscope-i-stream-you-stream-apps-stream-for-35yd85t6mq.pdf

Meerkat and Periscope: I Stream, You Stream, Apps Stream for Live Streams

Designing interfaces or applications that move beyond the bounds of a single device screen enables new ways to engage with digital content. Research addressing the opportunities and challenges of interactions with multiple devices in concert is of continued focus in HCI research. To inform the future research agenda of this field, we contribute an analysis and taxonomy of a corpus of 510 papers in the cross-device computing domain. For both new and experienced researchers in the field we provide: an overview, historic trends and unified terminology of cross-device research; discussion of major and under-explored application areas; mapping of enabling technologies; synthesis of key interaction techniques spanning across multiple devices; and review of common evaluation strategies. We close with a discussion of open issues. Our taxonomy aims to create a unified terminology and common understanding for researchers in order to facilitate and stimulate future cross-device research.

/pdf/cross-device-taxonomy-survey-opportunities-and-challenges-of-2rubom7yex.pdf

Cross-Device Taxonomy: Survey, Opportunities and Challenges of Interactions Spanning Across Multiple Devices

We wish you a warm welcome to CHI 2001. The CHI Conference provides a forum for people to meet both formally and informally, to share and to learn. We trust that you will find here the intellectually exciting and personally rewarding experiences that bring people back to this conference year after year.

CHI '01 Extended Abstracts on Human Factors in Computing Systems

A continuous, functional representation of a large set of head-related transfer function measurements (HRTFs) is developed. The HRTFs are represented as a weighted sum of surface spherical harmonics (SSHs) up to degree 17. A Gaussian quadrature method is used to pick out a set of experimentally efficient measurement directions. Anechoic impulse responses are measured for these directions between a source loudspeaker and the entrance to the ear canal of a head-and-torso simulator (HATS). Three separate SSH analyses are carried out: The first forms a SSH representation from the time responses, with the variable onset delay caused by interaural differences intact, by applying the analysis to each time sample in turn. The second SSH model is formed in exactly the same way, except using impulse responses in which the variable onset delays have been equalized. The final SSH analysis is carried out in the frequency domain by applying the technique on a frequency bin by frequency bin basis to the magnitude and unwrapped phase responses of the HRTFs. The accuracy and interpolation performance of each of the computed SSH models is investigated, and the usefulness of the SSH technique in analyzing directional hearing and, particularly, in spatializing sounds is discussed.

Analyzing head-related transfer function measurements using surface spherical harmonics

360° video and Virtual Reality are powerful techniques for giving viewers a sense of `Being There' [1], and are becoming increasingly popular. However, giving the viewer the freedom to look around also results in a reduced ability for filmmakers to direct the viewer's attention, a serious impediment to successfully telling a story within a 360° environment. We have created a number of 360° clips, filmed in such a way as to demonstrate and test several unobtrusive techniques for directing a viewer's attention within a 360° panorama. We have evaluated these techniques in a user study in which participants viewed these clips using a head-mounted display. Qualitative and quantitative data from these tests have been analysed to evaluate the effectiveness of the different attention-directing techniques. Qualitative data was also captured to explore the effect of the camera being addressed directly, and the viewers' responses to action occurring at a range of distances.

Directing attention in 360-degree video

The term `object-based media' has become commonly used to describe the representation of media content by a set of individual assets together with metadata describing their relationships and associations. At the point of consumption these objects can be assembled to create an overall user experience. The precise combination of objects can be flexible, and responsive to user, environmental and platform specific factors. An object-based approach like this can serve end users more effectively; by optimising the experience to best suit their access requirements, the characteristics of their playback platform or personal preferences. This paper presents an overview of the key characteristics and potential benefits of Object-Based Broadcasting and a case study of an object-based audio documentary, which can change duration in response to implicit or explicit input from a listener. Further examples will be given to illustrate the capabilities of a future object-based broadcasting system.

Object-based broadcasting - curation, responsiveness and user experience

There is increasing interest in providing content to users on secondary devices while they watch TV. This material, termed companion content, can be anything from textual information, to interactive quiz games. It can be delivered throughout a broadcast and often directly relates to specific scenes in a show. This new scenario has exposed a challenging design space for creators of both the content and the enabling technology. A key question when introducing content on a secondary device is how much it detracts from, or enhances, the show the user is currently engaged with. To examine this, we investigated methods for mediating attention from the TV and onto a secondary device. By examining a typical use case we have been able to gain new insights into how best to design additional stimuli to alert users to companion content from both a broadcasting, and an HCI perspective.

Mediating Attention for Second Screen Companion Content

Mobile devices are playing an increasingly important role in leisure activities, including TV viewing. Broadcasters see this as an opportunity to enhance a TV programme through the provision of additional information to the 'second screen', but determining how to optimise this experience is one of the grand challenges currently facing content providers. Addressing this issue requires a detailed understanding of interaction with both the TV and the secondary device, but this new form of HCI, as much about passive consumption as active interaction, is not well represented by typical task-based paradigms. This paper describes experiments that use eye tracking to understand one of the key components of this new area of study - determining which device is currently receiving the user's attention - and discusses the considerable challenge of accurately monitoring attention while maintaining ecological validity.

https://dl.acm.org/doi/pdf/10.1145/2559206.2578869

Michael Evans

Papers

Analyzing head-related transfer function measurements using surface spherical harmonics

Directing attention in 360-degree video

Object-based broadcasting - curation, responsiveness and user experience

Mediating Attention for Second Screen Companion Content

HCI over multiple screens