Unveiling the Magic of Spatial Audio: From Mono to Ambisonics

Ever wondered how some tracks sound "wide" or how explosions in movies seem to surround you? It all comes down to the concept of stereo image and how audio professionals manipulate our perception of sound location. In this blog post, we will explore the various techniques used to create multi-channel spatial audio and trick our brains into "locating" sounds.

1. Mono Sound:
Mono, the oldest and simplest form of sound reproduction, uses a single audio channel. In mono, there is no difference in the signals reproduced on both speakers, resulting in a lack of psychoacoustic localization. Despite being less common today, mono audio is still used in certain applications like radio broadcasting due to its simplicity.

2. Stereo Sound:
Stereo, the most prevalent format for modern music, consists of two channels - left and right. By manipulating the left and right channels separately, engineers can create a sense of "width" or spatial dimension. Amplitude differences between the channels allow our brains to locate sounds based on their positioning in the stereo field.

3. Surround Sound:
In surround sound, multiple channels are mixed together to create a more immersive experience. A standard 5.1 surround setup includes five full-bandwidth channels and one Low Frequency Effect (LFE) channel. Speakers placed around the listening position allow sounds to be positioned not only left and right but also at the back. This expanded soundscape enhances the audio experience, particularly in film and home theater settings.

4. Ambisonics:
Ambisonics takes spatial audio to the next level by introducing three dimensions - width, height, and length. It allows sound to be positioned in a sphere around the listener, simulating a truly immersive experience. Ambisonic systems, such as Dolby's Atmos, utilize ceiling speakers to achieve height effects. The beauty of ambisonic audio is its ability to automatically downmix for systems without specialized speaker installations, providing flexibility in delivery formats.

5. Creating Ambisonic Recordings:
Creating ambisonic recordings can be done using various microphone positioning schemes and arrays. However, the most common technique involves using mono sound and software capable of sending sounds around a three-dimensional field. By assigning directional vectors and velocities to mono sounds, engineers can create realistic movement within the ambisonic sphere. Stereo "beds" are often used as a foundation, with mono sound objects placed or moved around to enhance the immersive experience.

While stereo remains the standard for music production, the possibilities offered by surround sound and ambisonics are revolutionizing audio technology. With ambisonics already being explored in film and some engineers venturing into music, the journey to fully harnessing the spatial dimensions of sound has only just begun. Have you experimented with non-stereo formats? Share your thoughts in the comments below.