If you are an Apple fanboy or use an iPhone, you would have probably come across the term “Spatial audio” at some point, especially if you use Apple Music or if you have shopped for a TV, a sound bar or a speaker in the last couple of years, you also would have come across the term “Dolby Atmos”, and you ask yourself the 64 million dollar question, what does this mean for my listening experience?
Speakers have come a long way from when they were developed in the Johann Philipp Reis in 1861 to where they are now. We have seen innovation from having a single-channel(mono) playback to a two-channel(stereo) playback and more recently a multi-channel playback. We have also seen technologies like sound bars, in-wall speakers and subwoofers become more popular in recent times.
Mono vs Stereo
Because our ears are placed on opposing sides, the only way for you to listen at equal volume to what a specific source of sound is broadcasting is to place the said source of sound in your front, in the middle of your face to be specific. If you place the sound source far into your right to your left, you can, with your eyes closed, to some degree of accuracy tell where the sound source is located, this is referred to as sound source localization.
Here's a quick exercise that may not apply to everyone, but can help differentiate between two types of audio playback. Have you ever been listening to something with earphones and it sounds like both earphones are playing the same content? If so, the audio was likely in mono playback. If you can tell that there is a difference between the content played by both earphones, then the audio is in stereo playback.
Whatever you were listening to, in the later part of our exercise, was coming from two points, one on your left and one on your right. This creates the illusion of the sound coming from a wider space, and you can more easily distinguish between different instruments and sounds.
Another thought experiment.
Let’s say you are seated far back in a cinema, and remember, they use speakers, you don’t have the privilege to use earphones plugged straight into the source output. What do you think the audio experience is going to be like? Yep, you imagined right, painfully boring and not immersive.
But thank heavens, we can only imagine this, this is not what we experience in cinemas otherwise they would be pretty much obsolete today. Why would you want to pay cinemas for an experience that is more or less similar to what you get in the comfort of your home?
Everyone say hi to “Surround Sound”.
Surround Sound
Also referred to as a multi-channel playback setup distribute sounds around the 3D space in different segments giving granular control over the sound’s output. This is what happens in cinemas and yes, home theatre setups.
Sound location is broken primarily into Left(L), Center(C), Right(R), (and an optional Back (B)) and with these infinity stones, you can shape (with compatible speakers) your listening experience for the better by trying different combinations such as
- L-C-R (3 speakers.)
- B*-L-C-R (4 speakers, with the Back speaker placed directly in front of the Center speaker.)
- LB-L-C-R-RB (5 speakers.)
- LB-L-C-R-RB-B* (6 speakers.)
- LB-L-LC-C-RC-R-RB (7 speakers.) Yes, smartypants, we are swimming in familiar waters.
- etc
And this is where the “surround” in surround sound comes in. It provides you with a great deal of detail and immersion that increases the quality of your listening experience.
It is noteworthy that many things affect the sound quality in a surround sound system, and you can’t just place the speakers however you deem fit. There is a need for the right balance between your speakers to achieve the desired effect. At the simplest level, it is a mix of distance, position and direction. The rear speakers shouldn't be placed too far or too near to you. The front speakers should not be placed too high or too low and they must all be facing the right direction otherwise they might sound muffled.
While these speaker configurations account for most of the sounds you hear in a surround sound speaker setup, you will notice that it doesn't account for the subtle bass effect or the overhead rumbling of thunder you hear in a cinema. These are made possible because of Low-frequency Effect (LFE) or Subwoofer* and overhead speakers respectively.
Quick note
While similar, the LFE channel is not the subwoofer output and it is easy to mix them up since they function — output low frequencies, the same way. The main difference between these two channels is in the amount of information that they carry. The LFE channel broadcasts additional bass information added during surround sound programming while the subwoofer outputs bass information from the other main channels selected for reproduction. However, a subwoofer can broadcast output from the LFE channel.
In a traditional surround system, we are only concerned with the speakers and the subwoofers. With that out, we can talk about X.Y surround sound speaker notation. The X in X.Y. refers to the number of traditional speakers in the setup, while the Y refers to the number of LFE/subwoofers. For example, a 5.1 setup would have five traditional speakers and one subwoofer.
Dolby Atmos and Spatial Audio
Dolby Atmos and Apple’s Spatial Audio are specific implementations of enhancing audio experiences.
Dolby Atmos is an improvement on the Surround sound technology. It adds height channels to the traditional surround sound technology. It uses a combination of channel-based and object-based audio to create a more immersive and realistic audio experience. This extends the surround speaker notation from two to three, X.Y.Z. The additional Z refers to the number of height or overhead speakers. That means a 5.1.4 setup would have five traditional speakers, one subwoofer, and four height speakers, providing a more immersive listening experience.
Dolby Atmos is used in different settings, including movie theatres, home theatres, and even mobile devices. To fully experience Dolby Atmos, one needs a compatible sound system capable of playing back-the-height channels. Many movies and TV shows are mixed in Dolby Atmos, providing a more immersive listening experience.
Spatial audio, on the other hand, is a technology that enhances the audio experience by creating a three-dimensional sound environment. This technique that allows sound to be perceived as coming from various directions, — above, below and all sides, and distances, rather than just the traditional stereo left and right channels.
Soundbars
So let’s say you can’t afford a surround sound setup and you want to upgrade your TV’s audio output or you don’t have enough space to place the speakers around, soundbars are waving at you with the vim of a five-year-old waiting for their turn on the seesaw.
They are long, slim speakers that sit beneath your TV and provide a virtual surround sound experience. Many soundbars also come with a subwoofer that provides the extra bass that is missing from the slim soundbar. Some soundbars also integrate Dolby Atmos.