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How to Design a Telepresence Room

With travel costs rising and companies growing ever more global, it isn't always possible for colleagues to meet in person. A well designed telepresence room can only add to the effect of being where you aren't.

With travel costs rising and companies growing ever more global, it isn't always possible for colleagues to meet in person. Video teleconferencing (VTC) has long been an option, but even that seems so last century compared to what AV pros can enable today.

Manufacturers such as Cisco, LifeSize, Polycom, Tandberg, and others have started pushing VTC and the design of teleconferencing spaces to the limits of their capabilities in an effort to reduce or eliminate as many of the communication filters inherent to VTC as possible. They've even given this VTC on steroids a name–telepresence.

Technology filters–factors that often render the VTC experience underwhelming–are well known: inadequate bandwidth, inconsistent audio, poor lighting, and lack of interoperability, to name a few. But the biggest filters relate to human ergonomic and personal communication issues–issues that merely underscore the fact that the person you're meeting with really is in another room, far away.

It turns out the design of a room and the placement of technology within the room can have more impact on the quality of a virtual meeting experience than the actual technology used. Just as the right conference room design will maximize the AV systems in that room, the right telepresence room design will create a truly immersive meeting experience. Here's how.

Defining the Experience

First, what exactly does the term "telepresence" mean? "Teleconferencing" literally means "to confer (or meet) at a distance." As you think through the that definition, you can form a good mental image of what is intended. Telepresence, however, should paint an entirely different picture. How do you achieve "presence at a distance?"

Pete Nutley, director of global product marketing at Tandberg, describes telepresence this way: "It's a video meeting experience that creates the feeling of being across the table from the remote participants."

In order to achieve this experience, all participants are seated at a pre-determined distance from their respective cameras so as to appear life-size to the people at the far-end of the network connection. High-resolution, low-latency video, coupled with high quality directional audio help create this effect. And other visual cues–all telepresence rooms painted the same wall colors, equipped with the same lighting, and outfitted with the same furniture–round out the design.

"So telepresence really is about the experience," Nutley says. "When one or more of the criteria, such as background, distance from camera, desk color, etc., is not met, the experience of being in the same room deteriorates."

Jeff Machtig, co-founder of Digital Video Enterprises (DVE)*, which designs and sells telepresence solutions, agrees. "Psychology dictates that there are certain key elements that allow for effective communication and interaction between two or more individuals. How successfully we relate to one another depends greatly upon eye-to-eye contact."

The human factors of communication, therefore, are as or more important than the technology itself. The goal is to design a facility–technology and space working together–that fools the participant into thinking they are in the same space as the individuals they are meeting with. In other words, minimize the filters and distractions and make them as transparent as possible by paying close attention to several factors.

This story was edited to correct the name of Machtig's company, Digital Video Enterprises (DVE)

Factor 1: Acoustics

Setting up and coordinating camera, display, and furniture so that it looks like both parties are sitting at the same table helps facilitate better communication, especially in situations where telepresence meetings could go on for hours.

Setting up and coordinating camera, display, and furniture so that it looks like both parties are sitting at the same table helps facilitate better communication, especially in situations where telepresence meetings could go on for hours.

Credit: Brad Grimes

Although we're discussing video teleconferencing, let's start with the pieces of the puzzle that usually spawn the most complaints–the acoustical environment and audio system. It's relatively easy to demonstrate why these would be an issue in telepresence applications. Take a small handheld recorder into a conference room with you and record what you hear for five minutes. In fact, do it twice–once while you're in the room and once when you are out of the room. As you listen to the recordings, you will be very aware of all the background noise.

It is possible for people in a source room, i.e., the telepresence room they're sitting in, to ignore much of this. It's almost impossible for listeners at the remote site to do the same. The audio network is carrying both signal and noise, which means colleagues have to work harder to pull useful information out of the link.

The areas to address here are ambient noise levels, reverberation time or decay rates, microphone and loudspeaker placement, and system bandwidth.

One of the key contributors to clearly understanding the spoken word is the level of background noise (those sources that do not contribute positively) in the communication environment. Ideally, this level should be in the range of NC-30, which is roughly equivalent to a measured level of 36 to 38 dB(A) and is what the listener hears from a very quiet room fan at low speeds.

If the noise level exceeds 40 dB(A), it can be distracting to the listener trying to concentrate or stay focused on studies. Contributors to ambient noise include traffic (automobiles and aircraft), airflow from HVAC systems, elevator machinery, hallway conversations, lighting ballasts, and footfalls from the floor above, to name just a few.

People usually compensate for high ambient noise levels by either moving closer to one another or by raising their voices. Neither of these options is really viable in the telepresence environment, so the problems have to be addressed at the source. Careful attention to the room envelope (walls, ceilings, floors, doors, and windows), HVAC system design, and type of lighting used will help mitigate these problems.

Of equal importance is the reverberation time or decay rate of the room. Most people are familiar with reverberation; it's based on a uniform distribution of acoustic energy and random directions of propagation that can usually be achieved in larger rooms. There are a number of formulae that have been developed to help calculate reverberation time. In general, reverberation time increases with room size or volume and varies inversely with the amount of absorption in the room.

However the available formulae aren't very accurate for the smaller rooms in which telepresence systems might be deployed. For that reason, we should look at the acoustic decay rate of the room (the reduction of acoustic energy measured in dB/second). This is a measure of how quickly the acoustical energy in a space decays after the room is excited.

A "fast" room decays more rapidly (120-240 dB/s), which contributes to higher speech intelligibility and a greater sense of acoustical intimacy for the listener. Most telepresence rooms are quite small, or should be, and should hold no more than 10 to 12 participants at the most. At roughly 30 square feet per person, this translates to a room of roughly 300 to 400 square feet and an overall volume between 2,400 to 3,200 cubic feet. At this size, careful attention should be paid to room shaping and reducing resonant nodes.

Factor 2: Speakers and Mics

In a well-designed room, loudspeaker placement is less critical than microphone placement, but only slightly less. The listener on one end should be able to localize on who at the other end of the teleconference is speaking. This will typically mean placing a loudspeaker above the image of the person speaking.

Some manufacturers have included this ability in their audio signal processing equipment, and can recreate a reasonable sound field using two loudspeakers (see "Advancing the Art of Positional Audio," page 34). It isn't necessary to use a lot of loudspeakers, or that they be capable of extremely high sound pressure levels. After all, the goal is to recreate speech levels at the listener's ears in a conference room. This means that measured sound pressure levels should be between 66 and 69 dB(A) at the listener's ears.

Proper microphone placement will contribute to that sense of intimacy and increased intelligibility. Ideally, each participant should have a microphone, and have it as close to their mouth as possible. This results in a higher ratio of direct sound to reverberant sound at the microphone capsule. It also means less noise from shuffled papers, pagers, or other distractions.

If cost prohibits the use of personal wireless systems, there should be no less than one wired microphone for every two meeting participants, preferably mounted 18 to 24 inches from the front edge of the conference table. It is possible to use ceiling-mounted microphones, if proper attention has been paid to HVAC noise, vibrations, and the other ambient noise and decay rate issues. This is usually a choice of last resort, however.

All that said, carefully placed hypercardioid microphones can be placed further from meeting participants. It is possible to retain the sense of aural intimacy and also reduce noise from shuffling papers while "hiding" the microphones a bit further away. Some manufacturers have begun producing phased arrays of microphones to achieve similar results.


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