This chapter provides an overview of virtual auditory space, focusing on the context, acoustics, and psychoacoustics relevant to 3-D sound systems. It discusses the components of virtual reality and multimedia systems, distinguishing between natural and virtual spatial hearing. The chapter also covers the source-medium-receiver model, which describes the transmission path from sound source to listener, and the importance of understanding both natural and synthetic spatial hearing. Additionally, it explores the application types of virtual reality and multimedia, highlighting the differences between them and the role of sound in enhancing immersive experiences. The chapter emphasizes the need for a comprehensive understanding of psychoacoustics and engineering to design effective 3-D sound systems.This chapter provides an overview of virtual auditory space, focusing on the context, acoustics, and psychoacoustics relevant to 3-D sound systems. It discusses the components of virtual reality and multimedia systems, distinguishing between natural and virtual spatial hearing. The chapter also covers the source-medium-receiver model, which describes the transmission path from sound source to listener, and the importance of understanding both natural and synthetic spatial hearing. Additionally, it explores the application types of virtual reality and multimedia, highlighting the differences between them and the role of sound in enhancing immersive experiences. The chapter emphasizes the need for a comprehensive understanding of psychoacoustics and engineering to design effective 3-D sound systems.