Parametric Time-Frequency Domain Spatial Audio

Ville Pulkki, Symeon Delikaris-Manias, Archontis Politis, Ville Pulkki, Symeon Delikaris-Manias, Archontis Politis

• Publisher: Wiley-IEEE Press
• Year: 2017
• Print ISBN: 9781119252597
• eBook ISBN: 9781119252610
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

A comprehensive guide that addresses the theory and practice of spatial audio

This book provides readers with the principles and best practices in spatial audio signal processing. It describes how sound fields and their perceptual attributes are captured and analyzed within the time-frequency domain, how essential representation parameters are coded, and how such signals are efficiently reproduced for practical applications. The book is split into four parts starting with an overview of the fundamentals. It then goes on to explain the reproduction of spatial sound before offering an examination of signal-dependent spatial filtering. The book finishes with coverage of both current and future applications and the direction that spatial audio research is heading in.

Parametric Time-frequency Domain Spatial Audio focuses on applications in entertainment audio, including music, home cinema, and gaming—covering the capturing and reproduction of spatial sound as well as its generation, transduction, representation, transmission, and perception. This book will teach readers the tools needed for such processing, and provides an overview to existing research. It also shows recent up-to-date projects and commercial applications built on top of the systems.

• Provides an in-depth presentation of the principles, past developments, state-of-the-art methods, and future research directions of spatial audio technologies
• Includes contributions from leading researchers in the field
• Offers MATLAB codes with selected chapters

An advanced book aimed at readers who are capable of digesting mathematical expressions about digital signal processing and sound field analysis, Parametric Time-frequency Domain Spatial Audio is best suited for researchers in academia and in the audio industry.

Part I
Analysis and Synthesis of Spatial Sound

1
Time–Frequency Processing: Methods and Tools

Juha Vilkamo¹ and Tom Bäckström²

¹Nokia Technologies, Finland

²Department of Signal Processing and Acoustics, Aalto University, Finland

1.1 Introduction

In most audio applications, the purpose is to reproduce sounds for human listening, whereby it is essential to design and optimize systems for perceptual quality. To achieve such optimal quality with given resources, we often use principles in the processing of signals that are motivated by the processes involved in hearing. In the big picture, human hearing processes the sound entering the ears in frequency bands (Moore, 1995). The hearing is thus sensitive to the spectral content of ear canal signals, which changes quickly with time in a complex way. As a result of frequency-band processing, the ear is not particularly sensitive to small differences in weaker sounds in the presence of a stronger masking sound near in frequency and time to the weaker sound (Fastl and Zwicker, 2007). Therefore, a representation of audio signals where we have access to both time and frequency information is a well-motivated choice.

A prerequisite for efficient audio processing methods is a representation of the signal that presents features desirable to hearing in an accessible form and also allows high-quality playback of signals. Useful properties of such a representation are, for example, that its coefficients have physically or perceptually relevant interpretations, and that the coefficients can be processed independently from each other. The time–frequency domain is such a domain, and it is commonly used in audio processing (Smith, 2011). Spectral coefficients in this domain explain the signal content in terms of frequency components as a function of time, which is an intuitive and unambiguous physical interpretation. Moreover, time–frequency components are approximately uncorrelated, whereby they can be independently processed and the effect on the output is deterministic. These properties make the spectrum a popular domain for audio processing, and all the techniques discussed in this book utilize it. The first part of this chapter will give an overview of the theory and practice of the tools typically needed in time–frequency processing of audio channels.

The time–frequency domain is also useful when processing the spatial characteristics of sound, for example in microphone array processing. Differences in directions of arrival of wavefronts are visible as differences in time of arrival and amplitude between microphone signals. When the microphone signals are transformed to the time–frequency domain, the differences directly correspond to differences in phase and magnitude in a similar fashion to the way spatial cues used by a human listener are encoded in the ear canal signals (Blauert, 1997). The tim...

Table of contents

• Cover
• Title page
• Copyright
• List of Contributors
• Preface
• About the Companion Website
• Part I Analysis and Synthesis of Spatial Sound
• Part II Reproduction of Spatial Sound
• Part III Signal-Dependent Spatial Filtering
• Part IV Applications
• Index
• EULA