Sound channels and 3D audio explained

Sound channels

If you are confused by the unconventional naming of audio channel configurations such as 2.1, 5.1, and 7.1, then you are not alone, but we are here to help!

The use of decimal points in these notations might seem confusing at first, but they have a specific meaning and history in the world of audio technology. Here’s the explanation:

  1. Main Channels:
    • The integer before the decimal point represents the main channels, which are typically responsible for reproducing the primary audio content, such as dialogue and music. These main channels are usually speakers placed around the listener. For example, in 5.1, there are five main channels.
  2. Subwoofer:
    • The number after the decimal point indicates the presence of a subwoofer, which is responsible for handling low-frequency bass sounds. A “.1” indicates the addition of a subwoofer to the setup.

So, the naming convention separates the main audio channels from the subwoofer, which is used to reproduce low-frequency content. Here’s a breakdown:

  • 2.0: This configuration includes two main channels (left and right) and no subwoofer. It’s a basic stereo setup.
  • 2.1: This setup features two main channels (left and right) and a subwoofer for added bass, often referred to as a 2.1 speaker system.
  • 5.1: In a 5.1 setup, there are five main channels: front left, center, front right, rear left, and rear right, along with a subwoofer. It’s commonly used for home theater and gaming setups.
  • 7.1: A 7.1 configuration adds two more main channels to the 5.1 setup, providing a more immersive surround sound experience. This includes front left, center, front right, rear left, rear right, rear surround left, and rear surround right, along with a subwoofer.
  • 9.1, 11.1, etc.: Higher numbers indicate even more main channels and subwoofers, resulting in even more immersive audio experiences.

The use of decimal points in these configurations helps to clearly indicate both the number of main audio channels and the presence of a subwoofer. It’s a standardized way to represent the capabilities of an audio system, making it easier for consumers to understand the setup’s capabilities at a glance.

What is 3D audio?

Dolby Atmos and DTS:X are advanced audio technologies that go beyond the traditional channel-based audio configurations like 2.1, 5.1, and 7.1. Instead of being tied to specific channel numbers, these technologies introduce a more flexible and immersive approach to audio reproduction by incorporating object-based audio and sound positioning.

Object-Based Audio: In 3D sound systems, sound sources are treated as “objects” in a virtual 3D space. This allows audio to be precisely placed and moved in any direction within the virtual environment. This technology is commonly used in virtual reality and gaming to make the sound more realistic and interactive.

Let’s explore how Dolby Atmos and DTS:X relate to traditional audio channels:

Dolby Atmos

  • Dolby Atmos is an audio format developed by Dolby Laboratories. It’s designed to create a three-dimensional sound experience by using speakers positioned not only around the listener but also above and sometimes even below. It allows sound to be treated as “objects” within a 3D space.
  • Unlike traditional audio formats, Dolby Atmos doesn’t specify a fixed number of channels. Instead, it uses an object-based approach, allowing sound designers and audio engineers to position and move sound objects in a 3D space.
  • In a Dolby Atmos setup, you can have multiple speakers, including overhead speakers (usually ceiling-mounted or upward-firing speakers), to create a more immersive and accurate sound experience. Common configurations include 5.1.2 or 7.1.4, where the numbers indicate the traditional channels (5.1 or 7.1) and the decimal numbers represent the overhead or height speakers (e.g., two overhead speakers in a 5.1.2 setup).

DTS:X

  • DTS:X is a similar technology to Dolby Atmos developed by DTS (Digital Theater Systems). It also employs an object-based approach to audio, allowing sound objects to be placed in a 3D sound field. DTS:X can work with various speaker configurations.
  • DTS:X is highly adaptable and can be used with a variety of setups, from traditional 5.1 and 7.1 systems to more complex configurations with additional overhead or height speakers. DTS:X supports various speaker layouts, including 9.1.4, 11.1.6, and more.

Both Dolby Atmos and DTS:X are designed to provide a more immersive audio experience by offering sound from multiple directions, including above and around the listener. These technologies offer a significant improvement in sound positioning and realism compared to traditional channel-based audio systems.

Have a look at our selection of the best gaming speakers.

What about headsets?

3D audio in headsets of course doesn’t involve physical speakers placed around or above the listener’s head. Instead, it relies on advanced audio processing techniques, particularly Head-Related Transfer Functions (HRTF) and software-based simulations, to create the perception of sounds coming from various directions, including above and below.

HRTF is a crucial element in creating the illusion of 3D sound in headsets. HRTF is a set of mathematical functions that approximates how the human ears receive and process sound from different directions and distances. It considers factors such as the shape of the ears, the head’s size and position, and sound wave interactions. Each person’s HRTF is unique, which is why some headsets use software to customize your 3D audio experience.

Here is how 3D audio in headsets work:

  1. Drivers (Speakers): Headsets contain physical drivers that generate sound by vibrating to create air pressure waves. These drivers are responsible for converting electrical signals into audible sound. The drivers can be positioned near the ears, typically one on each side (left and right).
  2. 3D Audio processing: 3D audio processing, as described above under ‘object-based audio’, adjusts the audio signals sent to each earpiece (left and right) based on the position of virtual sound sources in the 3D audio space. This processing simulates the way sound would reach the ears naturally based on direction, distance, and elevation.
  3. HRTF and filters: In addition to adjusting audio signals for direction, HRTF and filters are used to replicate how the ear receives sound based on head size, ear shape, and other factors. These filters mimic the interaction between sound waves and the listener’s ears, making the sound appear more spatially accurate.
  4. Dynamic sound presentation: The audio signals are now played through the left and right drivers in the headset. As a result, you perceive the sound as coming from the specific directions and positions defined by the 3D audio processing.

Have a look at our selection of the best gaming headsets.