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Bench Talk for Design Engineers

Bench Talk

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Bench Talk for Design Engineers | The Official Blog of Mouser Electronics


Immersive Audio Is Like Life in a Speaker Cabinet Jon Gabay

(Source: Elaine Barker/Shutterstock.com)

Since the first days of monaural audio, re-created sound–both captured and stored for playback or live via transmission–has been a part of our lives. For the first time, re-created sound gave us freedom to listen to music when we wanted to and news when we needed to. It’s become a freedom that has expanded to become a need for almost everyone. Most people today say they need music to be happy, because both real and fake news, in some cases, can make us sad.

Although audio has migrated from mono to stereo, it wasn’t long before using more speakers became commonplace. With cheap amplifiers and speakers, anyone could turn their two-speaker system into an entire home audio system with a multitude of speakers. Using crossovers and equalizers, speakers could be optimized for bass, center band, or high frequency, allowing simple but effective surround sound and immersion. Low-cost, high-power amplifiers and speakers can let you blast sound louder than naturally possible, even to ear-damaging levels.

Theaters refined modern-day surround sound, and it has become reasonably priced for the masses. The popular 5.1 Dolby surround-sound system is effective, satisfying most listeners with an experience that captivates audiophiles, draws in movie buffs, and keeps gamers playing. Modern surround-sound systems dominated by Dolby 5.1 are adequate and satisfying for most audiophiles. The six-speaker setup comprises five full-band speakers and a subwoofer to allow placement of speakers to permit properly calibrated and recorded sounds to move virtually around the room.

However, more isn’t always better, especially when it comes to discerning speech. With so much sound coming from everywhere–enhanced bass rumble, and crystal-clear explosion–it is harder to discern what people say. Two solutions are shelving and dedicated speech center channels. Shelving takes speech-audio bands and subtracts other sounds in that band so that speech does not have to compete within band sounds. Center channels add dedicated center channels for enhanced speech bands. Surround-sound 6.1 and 7.1 configurations take advantage of this approach.

Today’s predominant philosophy is that more is better, so you can always upgrade to surround-sound 7.1 configurations, adding more channels and more speakers. In addition to front left, right, and center, and left back and right back, you will also have left and right sides. If that is not enough, a 9.2 configuration is an option. This 10-channel approach uses nine full-range speakers and a woofer to literally surround you and virtually put you inside a speaker cabinet.

How much is too much?

Don’t forget: Although many Dolby 5.1 surround-sound albums, CDs, and audio files are now available mastered to fully take advantage of 5.1, most of the media you will be listening to started from stereo and was processed into the six audio streams that became 5.1. This means the audio quality might depend more on how the original stereo was mixed and how effective the software is that converted stereo to 5.1. With 6.1, 7.1, 9.2, and so many other variations, the same is true. It is audio interpolation, not true location-dependent audio.

The latest immersive sound technology breaks away from actual audio recording to create an object-oriented database of sound. It is more than just adding speakers and amplifiers. Immersive technologies such as Dolby Atmos is a digital object-oriented approach that performs signal processing on discrete audio objects. For example, an airplane engine is an object that the immersive audio system will be informed about through metadata that accompanies the object. Not only is the audio sequence captured, but its location in 3-D space is presented to the audio processing system, which attenuates and moves the sound from speaker to speaker actually to mimic the sound of a noisy object in motion.

Unlike many of the surround-sound technologies, the immersive Dolby Atmos supports ceiling speakers, letting you hear, for example, that airplane engine right above you. Dolby 9.2 also does, but Atmos supports up to 128 channels with 118 objects, including 10 channels dedicated to ambiance effects.

Although movie theaters, stadiums, IMAX systems, and professional locations can use all 64 speakers, home theater systems are optimized for just 34.

Note that the placement of each speaker and its characteristics is very important. Atmos systems must be calibrated to be fully effective. This is why full-blown Atmos systems, such as those in movie theaters, will want to use all 64 channels.

Can you hear a difference? Maybe some can. It’s akin to reproducing signals only your dog can hear. Some will argue, for example, that the ultrasonics add to the richness of the experience, and even though we might not be able to hear these signals consciously, they still can affect us. It is true ultrasonics can cause agitation and irritation with prolonged exposure to certain inaudible frequencies. It is also true that ultrasonics in stereo can cause intracranial audio in the listeners’ head. No sound can be heard, but audio is re-created as the difference between the two ultrasonic signals resolved by the brain.

Conclusion

A 34-speaker home theater is bound to be impressive, especially when set up properly. In the modern era of lockdown and being stuck inside with the family, more noise might be a good thing.



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After completing his studies in electrical engineering, Jon Gabay has worked with defense, commercial, industrial, consumer, energy, and medical companies as a design engineer, firmware coder, system designer, research scientist, and product developer. As an alternative energy researcher and inventor, he has been involved with automation technology since he founded and ran Dedicated Devices Corp. up until 2004. Since then, he has been doing research and development, writing articles, and developing technologies for next-generation engineers and students.


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