There are many market factors driving the growth of video conferencing, and manufacturers like Polycom and ClearOne have responded with better technology. These modern video conference systems offer bigger displays, higher resolution video, high definition audio quality, integration with mobile apps, and so on. However, if this advanced technology is installed in a poorly designed conference room, the results can be disappointing.

A good conference room design and system installation takes into many factors, including lighting, background color and patterns, camera and video display locations, microphone and loudspeaker type and placement, background noise, and room acoustics. This post will focus on ways that the room design can enhance or reduce the audio quality of the system. A follow-up post will provide more detail on good room design principles to get the best audio quality possible out of any videoconferencing system.

The advent of HD audio quality

Traditional video and teleconferencing systems relied on telephone connections for communication, which inherently limited the audio quality. For example, landline phones are filtered to a narrow range of frequencies that are most important to speech intelligibility. As a result, voices can still be understood, but they don’t sound as natural as they would if you were in the same room with the person. Compare these two audio files to see if you can hear the difference in quality:


unfiltered audio
 


audio with telephone filter

As we move away from landlines to cell phones and VOIP systems, there are other ways that audio quality can be compromised. High quality digital audio requires a lot of data and causes network congestion. Phone systems try to balance the audio quality versus the data usage by tweaking the bit rate, sample rate, frequency range, compression, etc. of the audio.

New video conferencing systems offer HD audio quality that is almost as good as CD quality sound. However, you need to have a high-speed network connection to support it. Increased processing power of equipment also allows manufacturers to improve features like echo cancellation, background noise cancellation, feedback elimination, microphone localization and beamforming, and so on.

The equipment has gotten much more sophisticated over the years. But what about your conference room? Is it worthy of that new HD video conference system?

How does the room affect the audio quality?

Imagine if you took a professional symphony out of a concert hall and made them play in a noisy warehouse. Even with the best musicians, the sound would be mediocre. Unfortunately many expensive video conferencing systems end up installed in the equivalent of a noisy warehouse.

One of the universal factors for audio quality is signal-to-noise ratio, and video conferencing systems are no exception. The “signal” (people’s voices) must be louder than the “noise.” Noise consists of several factors, some of which may not be immediately obvious:

  • Background noise in the source conference room is picked up by the microphones, such as HVAC noise, traffic noise, rustling papers, etc.
  • Reverberation (reflected sound) in the source conference room is picked up by the microphones and passed on through the audio system. A basic microphone cannot differentiate between direct sound and reverberation.
  • Background noise in the receiving conference room (HVAC noise, traffic noise, etc.) can obscure the sound coming from the loudspeakers.
  • Reverberation in the receiving conference room can muddy the sound from the loudspeakers and reduce intelligibility.
  • Noise generated within the equipment. Fortunately this noise is minimal and usually not a problem with HD video conferencing systems.

This list assumes that everyone in the conference is seated in a conference room. If someone in the meeting is on their cell phone or using a hands free system while driving, the noise introduced can be even worse.

The signal-to-noise ratio is greatly affected by the distance from the person talking to the microphone. In most cases, the background noise in a conference room is pretty consistent throughout the space. The signal level, on the other hand, falls off significantly as the distance from the person’s mouth increases.

The worst case is to have a ceiling-mounted microphone near a noisy HVAC diffuser. We have seen some situations where the microphone was only a foot or two from a noisy diffuser and more than six feet away from the person speaking. In that case, the noise can actually be louder than the signal!

At this point, you might say that none of this matters because my shiny new HD conferencing system includes echo cancellation, noise cancellation, source localization, and a host of fancy features that make a bad room sound great! It’s true that these features will help, but they are not enough to make a noisy warehouse of a conference room sound like a concert hall. To get the most out of your expensive equipment, you need to take the room into consideration too. The good news is that it’s not hard to do. In the next post we will cover good design principles for acoustics.

Continue to Part II…