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Showing posts with label Atmos. Show all posts
Showing posts with label Atmos. Show all posts

Atmos for headphones and binaural sound

We humans have only two ears, on the left and the right. If we can only intake sound from only two “sound sensors” how it possible for us for us to discern sound originating from every single angle? Not only from left and right, but straight ahead, directly behind us and even above and below us. Close your eyes and listen to your surroundings, you can pinpoint exactly where each source of sound is, but how is this possible?
Atmos for headphones converts multi-channel audio to binaural sound
The answer comes in two parts, brilliant engineering on the part of our outer ear and some accurate post-processing. Contrary to what most people think, the outer ear – the piece of cartilage known as the auricle – does have a purpose. Because of its shape its able to focus and reflect sound originating from the font and attenuate (slightly reduce) sound originating from the back. The frequencies are also slightly shifted and delayed. The audio processing regions of our brains are then able to use these slight changes to decode where the signal is coming from.
The outer ear focuses and changes the pitch of sound based on the originating angle.
When we wear headphones or earphones, our outer ear does not play a big part as the sound skips the audio tuning usually performed by the outer ear and directly goes into the middle and inner ear. The post-processing component does not get the required shifted frequencies and so does not decipher any direction and distance data – so you generally can’t feel or get a sense of the where the sound originates from.

However, a workaround to this is known as binaural recording, this uses a dummy head or a mannequin head with externa ears. Inside each ear is a microphone that records audio exactly how it is perceived inside the ear. Sound waves bounce off the dummy head and external ear reaching the microphone exactly how the dummy would hear it if it were a real human. When this is played back over headphones, the listener gets the perception of hearing the sound as though it has already bounced off the external ear, giving the perception of surround sound.
A binaural recording mannequin.
The dummy head is not used to record sound in movies, TV and games. Rather it is recorded in multiple channels (microphones) and designed to play back over the same number of speakers. Sound from these speakers are meant to bounce off your external ear and be processed by your brain. Hence you don’t get binaural and you can’t experience surround sound in a headphone.

This is the problem Dolby Atmos for Headphones seems to solve. Dolby Atmos for Headphones works by taking sound from multi-channel audio such as Dolby TruHD or Atmos and processing them in to binaural audio so it gives a surround sound experience. Atmos for headphones uses an algorithm that can create a binaural effect which can create virtual speakers in any angle and distance. With Atmos, it can tap into the object meta data and create infinite channels to create sound originating in any direction.

You don’t need an expensive headphone to experience amazing virtual sound You could even use an affordable Logitech or Shure headphone to get the same amazing effect. Read our reviews.

See also
Binaural recording image source - Licensed under under the Creative Commons Attribution 3.0 Unported license.

Dolby Atmos -- redefining sound

Dolby Atmos is indeed a revolutionary innovation, and it truly deserves the popularity it has gained in the last few years. Atmos is present in many forms and places, in theatres, home theatres,  headphones and even smartphone speakers. There are also ways it set it up using a sound bar or traditional 2.1 sound set up. But, how could the same technology exist in something as fundamentally different as a phones and theatres?

Dolby has over the years given us the ways and means of storing, transmitting and reproducing high-quality sound. They specialise in the way sound is stored. The so called encoding products are used to capture and store; and subsequently reproduce sound originating from various angles. They started with Stereo -- simple two channel; progressing to 5.1 and 7.1 TruHD sound. Each new offering was a significant jump from the preceding generation.
Photo by Nana Andoh on Unsplash
Dolby Atmos on the other hand is fundamentally different.  Each of the previous products store sound originating from an explicitly defined direction. Stereo has left and right. 5.1 has Left, Center, Right, Left Surround, Right Surround and a Bass output. Atmos does not have explicitly pre-defined directions. The recorder is free to choose and define any angle in a 3D space and record audio data that pertains to that specific direction. This opens up infinite possibilities to capture or artificially produce sound.

Consider the following scenario in a movie or game:
 A sports car, travelling north, is being chased by a cop car from the back and a helicopter just above the car. A cop appears from the North East, pulls out a gun and fires at the vehicle.  Instead of the traditional pre-defined sound angles, Atmos is free to create its own channels with its own originating angle and distance from the audience. From this scenario 4 distinct channels can be dynamically created:

  • Channel one: The runaway car's engines, due north, close to the audience.
  • Two: The chasing cop car, due south with a medium distance.
  • Three: The cop, due north-east, with a medium distance
  • Four: The helicopter straight above, distant.

Sound can then be encoded for each of these channels. This method best captures the precise locations and intensities of each sound source, hence accurately recording exactly what the person in the car would hear. 

Rendering or reproducing the sound is the essence of the Atmos magic. The individual channels are simulated using whatever equipment is available. A theatre with speakers in every direction will use only the speakers in those directions to generate sound, this is a big step-up from the older 7.1 standard which has a channel-limit and hence a direction-limit of 7-8. Each of the speaker arrays in the 7.1 system will have recorded all of the sounds from their particular vantage-points and hence will result in a slightly inferior sound quality in the individual channels (cross-channel distortion).

When playing Atmos content on a set-up, the decoder simulates all of the virtual channels it captures, taking into account the positioning of your speakers.You could arrange your speakers in anyway and so-long as the decoders knows the positioning, it will be able to decide which speakers to play sound originating from each of the virtual channels.

This truly gives you the best sound experience possible regardless of what your speaker set-up is. And with infinite channels, and infinite speakers, Atmos could be the very epitome of sound.

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