SOUND IDEAS
AUDYSSEY INNOVATIONS BLOG

When we launched Audyssey DSX one year ago, I never expected the incredible response that we received from home theater enthusiasts.  It turns out that the much dreaded SAF was less of a factor than I thought, and people will actually put nine or eleven speakers in their house.  Who knew?

Audio systems today have already reached the limits of human perception in frequency response and dynamic range.  Yet 5.1 channel surround sound is not completely convincing.  It can easily be distinguished from the real thing because human perception can hear many more directions than what current systems provide.  This is what we set out to address with Audyssey DSX.

But, if the gods grant us more channels, where should we place them?  The answers come from research in acoustics and psychoacoustics.  Our sense of “being there” is enhanced when we hear not only the direct sounds from the front, but also sounds that arrive later from very specific directions.  When our hearing starts to provide cues that match what are our eyes are telling us about the space, something magical happens: immersion. (more…)

Avatar 3D is showing to rave reviews in 2100 theaters, ESPN announced 85 sporting events broadcast in 3D starting with the FIFA World Cup in June, and all I heard about at CES was 3D televisions shipping this year.  It is a big deal.  I think… Or, it could be the next consumer electronics industry failed format.  There is no way to really know what 3D picture will become but there is huge momentum behind it and I think we are going to be hearing about it, watching it and talking about it for the next several years.

So, while we sit with our 3D glasses on being immersed in 3D video (and hopefully not getting headaches), I want to talk about 3D audio — because what’s the point of 3D video without an immersive audio experience?

Sound has an advantage over picture when it comes to rendering: the cues we receive from well designed and calibrated systems are closer to the real thing than what 3D displays can deliver.  Here’s what I mean by that:  I can stand behind a black acoustically transparent curtain next to a loudspeaker and with the right calibration make it so you can’t tell if it’s me or the speaker talking.  No display technology exists today that can fool you into thinking you are looking out of a real window. (more…)

Do you have a subwoofer in your system? Great. Then your speakers are small. Before you get all upset, read on. This is one of those audio myths whose time has come to be busted. To understand why, we need to talk about Bass Management.

In the early days of home theater it was thought that in order to reproduce the full movie surround experience at home it was necessary to place 5 large loudspeakers in the room. The reason for the size was the woofers. To play at theatrical reference levels and reproduce the deepest bass available in the content requires each speaker to have 12” or larger woofers. Let’s just say that this theory didn’t get very far in the real world.

A better and more practical approach came after studying human perception. The mechanisms that we use to determine the direction of arrival of sound depend on the frequency. At high frequencies the wavelength of sound is small and so sound coming from the side is shadowed by our head. That creates a level difference between the sound reaching the ear closest to the source and the ear on the other side. Our brain analyzes these level differences and produces an estimate of where the sound is coming from. But at lower frequencies, the wavelength of sound gets longer and our head is not large enough to produce a level difference at the two ears. Instead, we analyze the difference in time of arrival of sound at the two ears. Sound arrives first at the closest ear and we use that to determine the direction. But even that ability fails us below about 80 Hz. The wavelengths get very large and it was found in listening tests that 80 Hz is the frequency below which most people can not localize the direction of sound.

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Here is a trick question: “What if I correct the acoustical problems in my room, but I don’t like the resulting sound?” If you find yourself asking this question you have stumbled on the line between Reference and Preference.

Let’s look at what room correction aims to do. You start with a good (or not so good) set of speakers, you place them in a room and what you have is problems: acoustical problems. Sound from the speakers comes to you from many different directions. Some of it directly, but most of it after interacting with the floor, ceiling, walls, and furniture. Because each of these elements is at different distances from where you sit, the combined sounds arrive at slightly different times and what you hear is a form of distortion. Voices can sound unnatural, the low frequencies are muddy or boomy, and the high frequencies lack air and sparkle (yes, these are all technical terms).

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My first “beyond 5.1″ experience was in January 2000 at the Alexis Park Hotel in Las Vegas. My colleague from the USC Immersive Audio Lab, Tomlinson Holman, was in the small room next door explaining why more channels are needed. This was followed by a demonstration of the world’s first 10.2 system to a few members of the press.

The world of sound had come a long way from the introduction of the first stereo LP in 1957. But in fact, with 10.2 we were moving back in time. It was in the late 30s that researchers at Bell Labs had looked into the question of how many loudspeakers are needed to reproduce a seamless, realistic sound scene. The answer at the time was discouraging: it turned out to be an infinite number–not exactly a high SAF (spouse approval factor) idea. Two channel stereo, however, was the only way to deliver sound to the consumer and it was limited by the LP groove that had two sides. Certainly better than mono, it didn’t come close to delivering an immersive experience.

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