Acoustics and audio concepts
This article will cover some general concepts around audio and acoustics, such as reverberation and general rules of thumb for room setup, which will help when you are planning how to implement specific technologies to optimize your space.
This article covers:
- Acoustics (reverb issues)
- Signal-to-noise ratio (noisy rooms)
- Microphone concepts
- Speaker concepts
- Acoustic treatment specialists
For information regarding audio processing and acoustic echo cancellation, please refer to the Zoom Rooms audio guidelines with specifics around Zoom Rooms and technical processing.
Acoustics (reverb issues)
Acoustics is a very important aspect for any conference room. Reverberation in a room will always degrade the sound quality and intelligibility of a conference participant. Treatment (adding soft and non-flat surfaces) will allow the microphones to hear the audio source more directly, and will also help diminish the sound artifacts that may be residual in the room due to reverberation caused by hard surfaces such as walls, ceilings, glass windows, or conference room tables.
RT60 is a measurement expressing the time during which a sustained sound drops by 60dB after the sound stops. A general rule of thumb is to make sure that there is no more than half a second of reverb time based on RT60.
If the reverb time is higher than half a second in a space, another calculation can be applied for room treatment. As an example, for a room with an average ceiling height, 40% of the floor's square footage should be treated with sound-dampening solutions and/or should not contain hard surfaces in the space.
There are many sound-dampening solutions, such as acoustic paneling and ceiling baffles to help mitigate reverberation in a room, but—depending on how heavily a space needs to be treated— use of these materials can be expensive. Before consulting a specialist, think about what kinds of soft objects you can add to a troublesome space, such as bookcases, overflow soft seating, carpeting, canvas artwork, or plant life, all of which will help to dampen reverberations.
Signal-to-noise ratio (noisy rooms)
Signal-to-noise ratio is the relationship between the noise floor—or the ambient state of the room—as compared to the actual volume of the desired audio you are trying to capture and transmit. Ideally, the noise floor in any space is no louder than 40 dB SPL A-weighted. If you assume that a normal speaking voice is about 70 dB SPL A-weighted, then your signal-to-noise ratio is 70 dB minus 40 dB, equaling 30 dB, which would classify a room as an optimal candidate for conferencing.
The noise floor in a conference room can be affected by things like heating, air conditioning & ventilation (HVAC) systems, elevators, building mechanics, open-sales offices or trading floors, traffic, trains, planes etc. What actions can you take? When designing room layouts—and you are able to anticipate issues—using sound absorbing and sound-proofing materials such as:
- double-paned glass between a room and a busy street
- heavier wall and ceiling tiles with a higher transmission coefficient
- wall construction from floor to infrastructure ceiling (above ceiling grid)
- sound absorbing ceiling tiles
Use of these types of materials will be the best approach to reducing a room's signal-to-noise ratio.
Microphones take energy and convert it from one form to another; these types of energy-converting devices are also known as transducers. In this scenario, you are taking acoustic energy and turning it into electrical energy, and producing digital data.
There are a few variations for microphone configuration:
- All microphones are a part of the room-listening experience, with some processing to optimize the experience.
- Presentation microphones are prioritized for local voice lift and primary audio into the conference system. Additional room microphones may exist alongside in this scenario.
- A hybrid of the above two configurations. Typically seen in boardrooms with long gooseneck microphones for each seated participant, this setup utilizes the 3-to-1 rule: for every participant-to-mic distance of one, there will be a relative distance of three between microphones. This invasive model is a bit outdated.
Generally, it is desired that the video experience is seamless and invisible, so that participants will not know the technology is there.
In the conference room, new array-microphone technologies can now simplify and steer microphone pickup with more directive technology, which allows the microphone experience to be unnoticed—rather than being invasive—since being close in proximity to microphones is usually not preferred.
Speakers, another type of transducer, convert electrical energy back into acoustic energy, so that you can hear the digital data. Speakers can be thought of as the mouths of the video participants.
The conference phone in the center of the table has historically been the point of focus. This has translated into some room designs as an all-in-one speaker/mic unit on the table, with video participants on the wall. This is an unnatural experience, but in most cases, the all-in-one mic/speaker unit must function as both for it to work properly, as these kinds of devices (Poly Trio, Crestron Mercury, Logi Group etc.) have their own internal processor .
In a lot of Zoom designs, the speakers are put as close to the people on video as possible, since that is where where the attention is being focused. You are, after all, talking and listening to a face on-screen, which is just a recreation of the speaker's image captured by a camera—the technology becomes invisible.
To do this, you need to create a natural environment. In smaller huddle rooms, an all-in-one soundbar emits sound nicely, while combining a microphone and camera. In a standard conference room, a pro soundbar mounted near the displays work best. For larger conference rooms, you can run into the issue of lacking uniformity of the sound system in the space, which can be problematic. In much larger systems, it is preferred to distribute the audio so that all participants continue to have a good experience listening—without great volume fluctuation—regardless of the seating location.
Acoustic treatment specialists
Here is a small list of companies that will assist you with sound treatment in your space to optimize the Zoom Rooms experience.
Please feel free to reach out directly for consultation.
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