Frank Melchior

Spatial Sound With Loudspeakers and Its Perception: A Review of the Current State

This paper reviews the current state of loudspeaker-based spatial sound reproduction methods from technical perspective as well as perceptual perspective. A nomenclature is developed that allows for a strict separation between these two perspectives. The physical fundamentals, practical realization, and results from perceptual studies are discussed for a number of well-established and emerging reproduction techniques. Further, the paper outlines novel approaches to spatial sound evaluation in terms of perceived quality and provides a comparison of current approaches.

Object-based audio applied to football broadcasts

In this paper, we describe an object-based audio broadcast of a football match from Wembley Stadium, London. Listeners were given audio feeds from opposite ends of the stadium together with a commentary feed and were able to mix the balance between the three feeds using the HTML5 audio API. The experiment proved popular with the people who took part. Most listeners chose to set their preferred mix within the first minute of the broadcast and did not alter it as a result of events in the stadium. Also, preferred mixes were clearly observed.

Wave Field Synthesis and Object-Based Mixing for Motion Picture Sound

Digital Cinema and 3D pictures are the latest innovations for cinemas. Audio reproduction on the other hand, is nearly the same as it was in the late 1980s, when discrete multichannel audio was introduced. Even uncompressed storage and distribution, as well as the addition of a few more channels, did not change things significantly. Wave Field Synthesis (WFS) can change the situation because it offers spatial audio as a complement to 3D pictures. Using WFS, it is possible to focus sound sources inside the audience area. The sweet spot limitation of traditional multichannel audio no longer applies. On the production side, a complete new tool set is available for sound designers and mixers, based on object-based audio post-production. Although the basic principles of Wave Field Synthesis have been well-known for a long time, recent developments have made it possible to bring this technology into todays theaters. This article describes the current state of WFS in motion picture sound, as well as its unique properties and the benefit of object-based reproduction in the audio post-production process.

Next generation audio system assessment using the multiple stimulus ideal profile method

With the development of so-called next generation audio systems the question of evaluation of such immersive or object-based systems is of large interest for the industry. This paper presents the multiple stimulus ideal profile method for the practical assessment of next generation sound systems. The approach takes best practices from a number of different well-recognised methods as well as some novel ones from other industries. The paper presents the method as well as the initial results of the test using specially designed test items to investigate the characteristics of the method. Practical experiences in two labs with different listener groups and statistical analysis will be discussed in detail.

Exploring object-based content adaptation for mobile audio

Mobile devices enable users to consume media with audio content in a wide range of contexts, with environmental noise being present in many of these. Several methods exist that aim to improve the experience of mobile listening by utilising information about the environmental noise, such as volume and dynamic range adaptation. This paper explores a fundamentally different approach to improving the mobile listening experience by using the object-based audio paradigm, where individual audio sources are mixed in response to each specific listening context. Three experimental studies, containing both quantitative and qualitative aspects, are presented which investigate whether environmental noise influences preference of background-foreground audio object balance in a mix. The results indicate that environmental noise can influence the preferred audio mix and that the nature of the adaptations made is dependent upon both audio content and user. Additionally, qualitative analysis provides an understanding of the role of environmental noise on preferred audio mix. It is believed that the content adaptation method explored in this paper is a simple yet useful tool for adapting content to suit both the context and the user.

Correction to: Exploring object-based content adaptation for mobile audio

Due to miscommunication in the typesetting process, the following p values in “Exploring object-based content adaptation for mobile audio” require correction.

Optimization-based reproduction of diffuse audio objects

The creation of a diffuse sound event from a single audio signal is an important signal processing task, for instance in spatial audio reproduction or audio coding. Current algorithms based on decorrelation filters or frequency-dependent panning typically cause artifacts due to transients or time-domain aliasing. In this paper, we propose an optimization-based approach to diffusion that creates a set of filters to approximate a desired distribution of frequency-dependent propagation directions to create the perception of a diffuse sound field with a multi-channel audio system. Thus, the diffusion can be optimally adapted to a specific reproduction scenario. In addition, the transient response can be purposefully improved by imposing constraints on the time-domain filter coefficients.