View our Ultimate Holiday Gift Guide for 2008
Electronic House Newsletter   View sample
 
Popular Stories
View 40 winning homes. Best Home Theater, Family Room and more.
Recent Comments
Paul (01/06, 03:49 PM)
Paul (01/06, 03:34 PM)
Jason Unger (01/06, 02:33 PM)
j0hnny (01/06, 02:28 PM)
J0hnny (01/06, 01:09 PM)
Recent Slideshow Galleries
julian theater crawlspace theater iphone control Top Microsoft Exec Shows Off Media Center-Based Home kraft familyroom room tvflatpanel 8 Green Gadget Gift Ideas sharp flatpanel Powerful Accessories for Your Theater DIYer Adds Irish Flavor to Basement Theater Shopping Cart 8 Products for a DIY Theater Blu-ray Disc 2008: A Year in Review den popup Finding the Right Digital Photo Frame 12 Great Tech Gift Ideas for $100
Info and Answers Feature
3-D in Home Theater
Past, Present & Future of 3D
Once trendy in the 50s, 3-D is making a comeback with movies, video games and sporting events.


Themed Home Theaters
View Designing a Death Star Theater
Designing a Death Star Home Theater
Three separate rooms, one starfield, and a life-sized Han Solo are just a few of the things that help two super "Star Wars" fans get their geek on in this theater.

Site Sections
Services
Info and Answers
What is Aud­yssey’s Dynamic EQ and Dynamic Volume?
Audyssey’s Chris Kyriakakis explains how these automatic sound control features work and what we can expect in the future.
image

Audyssey has developed technology to correct sound distortion automatically.

Slideshow
image
View Slideshow

Also Filed in Info and Answers

November 06, 2008 | by Dennis Burger

If you have a passage of music that has loud and soft parts when you’re at high volumes, and then you lower the volume, the soft parts need more correction than the louder parts. So we had to invent a way of measuring perceived loudness in every channel, running in real time. And that’s what Dynamic EQ does. Every channel has its own loudness meter that looks at the content as its coming through and estimates—based on the signal and our human models—how a human will perceive it. So it makes minute adjustments, and of course it doesn’t just rapidly go up and down or you would notice it. We smooth it out. That’s part of the innovation here—that’s why we called it Dynamic.

So how did you develop the human model for this?
We work a lot with professional mixers at the university because of Tom [Holman]’s connections. So we did a number of experiments with them. In one of them we put them in front of the console and turned down the master fader, and the first reaction they had to their own mixes was, “what happened to my surrounds?” It turns out that loudness perception is spatial—it falls off faster behind us than it does in front of us. And we asked these mixers, “OK, you’re down 10dB, what would you do to the surrounds to maintain the surround impression?” And they would move it up, and at different levels they would move it up by different amounts. So if you do that with enough people you can come up with a set of rules that mimic what they’re doing.

So we integrated that into Dynamic EQ—as you turn the volume down, the surround levels go up a little or a lot, depending on how far down you are, to maintain the impression of surround. And the best way to demo that is to turn the volume down 20dB and turn off Dynamic EQ, and all of the sound collapses to the front.

How does Dynamic Volume fit into all of this?
So, continuing with our story of the mixers—we had probably 20 people who participated in this set of experiments, initiated by Tom Holman, who was puzzled for a long time by one particular problem: why is it that a mix that is done in the dubbing stage doesn’t work as well in our home theaters? Why do we need to keep adjusting the volume—up to hear the dialogue and down when the action gets heavy? Why do we need to do it at home, but not in the movie theater? We have high end equipment. What’s going on?

What we found was that the content is mixed for movie theater systems with extremely high dynamic range—very powerful amps, big speakers, in huge rooms. But when you bring that into the home the sound pressure levels that you perceive change, the perceived dynamic range changes, and it’s affected by the size of the room and the ability of your system. So the first thought was, We have to control the dynamic range, but we can’t do it by putting a compressor in the signal path, because that doesn’t work—it introduces artifacts.

By “compressor,” you mean things like Night-time Mode or Midnight Mode, and similar dynamic range controls on many A/V receivers, which make loud sounds quieter and quiet sounds louder...
Exactly. So to find a better solution, we brought mixers in to work with content that they knew and said, “Pretend your daughter is sleeping next door, and make adjustments to this mix in real time.” And we set up a system to electronically track their movements and in parallel record the content in 5.1. When we were done we had a seven- or eight-terabyte database that we gave to our research team and said, “We need to reverse engineer their decisions. Why did they turn the sound down when they did, and when they did turn it down how fast were they reacting? What were they reacting to? What was the content in every channel?” And we came up with an algorithm that mimicked those decisions. And so Dynamic Volume came out of these experiments. It uses a look-ahead method, with a small buffer, and looks at what’s about to play in each channel…

How far does it look ahead?
That’s adjustable. It depends on who we’re working with. A TV manufacturer will give us a lot because they’re already doing video processing and they don’t care. An A/V receiver manufacturer will not give us as much look-ahead time—it’s about half a frame. The more the better, obviously, but you don’t want to be introducing delay more than you have for video, so we’re limited by that. 

So, aside from the look-ahead buffer, what makes Dynamic Volume different from other dynamic range controls?
Well, the average person adjusts the volume level so dialogue sounds right. That’s what’s important to them. They just don’t want to have to run from the room when the explosions come, or at commercial breaks. So we keep dialogue as reference, and then monitor the signal above or below and decide how much to bring it up or down. The trick was to do that without using a compressor, as I mentioned before, because a compressor has a fixed time constant. If things are too soft it boosts, and if things are too loud it cuts. But it doesn’t have any knowledge of how quickly they’re becoming soft or loud. And so by the time it catches most things they’re already changing in the other direction.


This entry has been viewed 7340 times.

Article Topics

Social Bookmark   less


Comments (6) Most recent displayed first.
Posted by Mike  on  11/17/08  at  09:36 PM

Does Denon 1909 allow one to save several Audyssey configurations (flat, THX, etc) and then recall them according to media played?  I seem to be locked into the Audyssey flat mode, which is apparently not appropriate for TV, altho’ it doesn’t sound too bad to me.

Posted by Yiu  on  11/12/08  at  12:56 AM

So should i be using audyssey flat for all of my bluray or dvds?  Or only for movies done by New Line.

Posted by Matthew  on  11/08/08  at  09:46 PM

Great interview/article - informative while being easy to understand.  Audyssey’s dynamic EQ + dynamic volume sound like a great approach to improving real world listening.  Unfortunately my otherwise great AVR is a 2007 model, meaning it doesn’t have dynamic EQ or dynamic volume.  They will be must-have features in any future AVR I purchase.

Posted by Paul  on  11/07/08  at  01:38 PM

I’d have to agree with Hou,

Th difference between using the Audessy calibration and not on my Onkyo 805 is astounding.  I have a rectangular room 12x16x9 for my home theater, and never realized how much of the sound was muddled or muffled from what I’m assuming was room harmonics.  With the audessy system engaged, the simplest thing to say is it sounds much better.

Posted by LightningRod  on  11/06/08  at  05:04 PM

Wow!
First I have to say the whole Audyssey thing seems like it was well thought out and backed by a lot of empirical data (from all those expirements with human mixers). Second, the article was very informative and on solid technical ground, without a lot of confusing math or other stuff to get in the way of the concept. You really did a good job here kids.  Keep it up.


+ View all comments on for this article



Post a Comment

Name:

Email:


View comment guidelines

Remember my personal information

Notify me of follow-up comments?

Please answer the question below:

Type the 3rd letter of the word "woofer":





Learn more about products and solutions from tech companies.
Electronic House magazine's 2008 Best Homes of the Year special.
Electronic House reviews the coolest products of the year.
Get all the information you need to network your entire home.

Stay up-to-date with home electronics. Get your print subscription today.
Weekly email offers tips, info and product news.
Subscribe today!
Get the content that's important to you.
More about RSS.
Electronic House is now available in a digital edition. Learn more.
About us Advertise Magazine Newsletters Digital issues EH Publishing Privacy policy Contact us
 Copyright © 2006 EH Publishing. All rights reserved.
EH Network: CE Pro TecHome Builder ChannelPro ProSoundWeb Church Production Electronic House Expo Worship Facilities Expo