[AG-TECH] Echo canceller

Markus Buchhorn Markus.Buchhorn at anu.edu.au
Mon Jul 21 23:37:23 CDT 2003

At 14:43 21/07/2003 -0700, Ed Ritenour wrote:
>a lot of peoples time. Also remember if you use more than one mic its is a
>good idea to be able to mute the remaining ones, otherwise you do get
>background noise, such as people rustling papers, typing on a laptop or just
>a squeaky chair. Audio is what makes a meeting, without you may as well go
>home. Skimp on PC's and projectors, but invest wisely on audio.

I'd agree with this sentiment, on the impact of background noise - we decided to use ceiling mounted boundary mikes to cover the rooms in all 3 of our nodes (so far), with no ceiling mikes and no lapel mikes wanted or needed. I've seen a few sites where desktop mikes and poor autogating just killed the experience. But, muting mikes on-demand is a pain for somebody to manage. People are still the most expensive asset in a node.

One suggestion for Richard is to look at the Polycom ASPI EF2280, which is an 8+4 channel AEC; we found it was significantly cheaper (in Australia at least) than the notionally equivalent Gentner, and in most cases that Gentner's numbers were poorer than the ASPI's. We've used them now in our 3 nodes and I've been very happy with them. The software is damn cool too :-)

The single channel AEC's (EF400, for example) aren't always fully dynamic, i.e. they don't quickly adapt to changes in the room - e.g. doors opening/closing, people moving about and changing the acoustic characteristics of the room. The higher-end units do. I looked at it, and our acoustic engineer talked me out of it. The cost saving would have been fairly small anyway - the single-channel AEC plus a good mixer came to a close number of the EF2280, and had a lot less flexibility and scalability. The EF2280 is a full matrix/mixer with lots of additional bells and whistles to play with.

This is in rooms ranging from 8 seat boardroom to 105 seat lecture theatre.

I like the comment by somebody else, about "skimp on everything else but the audio" :-)


Markus Buchhorn, ANU Internet Futures Project,      | Ph: +61 2 61258810
Markus.Buchhorn at anu.edu.au, mail: Bldg #108 - CS&IT |Fax: +61 2 61259805
Australian National University, Canberra 0200, Aust.|Mob: 0417 281429

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