Stop reading for a moment and give a listen to what’s going on around you. What do you hear? Perhaps you’re hearing the distant sound of people in the next office or common area? Or maybe noise from the street below? Maybe even the air handler above? Do you find all that distracting now? I can tell you that AV professionals are obsessed with this kind of analysis, and do their best to determine what your space is intended to do with careful consideration as to how these external factors come into play.
While those noise sources aren’t necessarily the most prominent sounds you would hear in a conference room or lecture hall, their ability to interfere with speech intelligibility must be factored in to create a space where proper communication can take place, especially when a sound system is needed to bring audio and video communications to all of its participants. Early stage building design decisions should include consideration to the room’s materials in order for the audio to react favorably, especially when it becomes a critical part of that room’s function. In some cases, a room may be repurposed as a meeting or presentation space and its acoustic qualities must either be redesigned, or dealt with by the audio technology. But first, let’s take a step back and talk about typical workflows in some common room types found in the workplace.
Small Meeting Rooms
The simplest and usually most widely deployed types of spaces found in the work environment are huddle rooms and small conference rooms. These types of rooms don’t require a tremendous amount of equipment to make them suitable for employee collaboration. Display technology is relatively inexpensive with most manufacturers offering a variety of wired AV connections. But what about the audio portion of that technology? Does the display showing a presentation have speakers to playback any sound associated with it? Is there a way to inject sound from a source, such as a laptop? Typically, the answer would be yes to both, and to some degree, can be done with a relatively minimal amount of cabling and connectivity devices. And while smaller speakers that are integrated into the display will usually suffice, we find that additional speakers would be required to provide better performance in larger meeting spaces.
Now, what if there is a need for a meeting space to include conference calling capabilities? Many spaces can make do with a simple speakerphone. There are plenty of options for telephone technology including analog and VoIP speakerphones that can be expanded with additional mic and / or speaker “pods” for larger tables and rooms, as well as the same types of offerings with a USB connection for hosting calls using a PC or laptop.
Medium to Large Presentation and Conference Rooms
In larger rooms and conference tables, this expansion may still not provide enough range for people to be heard through the microphone system built into it, nor will its speaker translate well to those that are seated at the very ends of a larger table, or others outside of the seating area.
…On a side note, I recently attended an onsite construction meeting, where the meeting organizer got together all of the tradespeople around several tables set up in a U shape and proceeded to dial into the audioconference bridge with his smart phone. Now, hearing the participants on the other end of the call was difficult for those seated across from the phone, and for anyone who was not within a chair or two of that phone, participants on the far end were not able to hear them at all. As a representative of the AV integrator chosen to install presentation and audio/videoconferencing systems for our common client, I was happy that the groundwork was already in place to show the value of what we do…
Once you have gone beyond a room size that only allows for a few people to collaborate, you and possibly your AV integrator need to determine how to best provide an audio solution for a larger room and its participants. Medium to large rooms may still utilize displays with integrated or separate left and right speaker systems mounted at the front of the room for both presentations and audio or videoconferences. But in some cases, that audio may be required to be louder than typical listening levels so that participants can make decisions based on cues from audio content. In an environment where content is being created and then presented to a decision team, the AV system may need to have multi-channel audio, such as a surround sound system like those that would be found in a home theater. This can be achieved by wall mounted speakers strategically placed around a seating area, or with ceiling mounted speakers placed in a similar dispersion pattern. Ceiling speakers may be a better choice where either a room’s aesthetics are important, or ceiling heights restrict mounting speakers on wall surfaces due to ADA requirements.
For an audio or videoconference call in a larger sized meeting room, distributed ceiling speakers will better benefit the people in the room listening to those on the far end of the call. Ceiling speakers will also provide a benefit to the audio portion of a video presentation so that areas in the middle and rear of the space are hearing equal amounts of audio, rather than having to turn up the display or front of room’s speakers and subject the people seated closer to the display to either an uncomfortable or unsafe listening levels.
If the same room is to be designed with a maximum predetermined number of participants around a table, then a properly planned and installed solution can involve permanently fixed microphones which can guarantee proper pickup of people seated at that table. Microphone placement for a rectangular table of an average width (3-4′) can utilize microphones that have either multiple elements or a single element with an omnidirectional pattern (picking up sound from all directions), that are placed down the center of it. In other cases where room noise and/or room reflectivity is an issue, it is desirable to have microphones that have a narrow pickup pattern placed closer to the participants, and may only capture two chairs per element (see example below). This will cut down on the amount of room sound that is being picked up by the microphone elements.
For these large spaces, early stage audio design considerations must be discussed so that deploying the technology isn’t going to be difficult, expensive or worse, performing poorly. In most training rooms and town hall spaces, the primary focus is on the person at the front of the room giving a presentation and addressing the rest of the room. If that person relies on a podium to present from, then a wired microphone would typically suit the application and can be neatly dressed and terminated to a floor box below the podium. Microphone wires have to be properly managed so that people aren’t coming into contact with them and possibly damaging or disconnecting them. But if the presenter is required to move around, then a wireless microphone solution should be considered to avoid microphone wires exposed across a floor. A hand held wireless microphone will typically suffice for most presenters who are able to use a microphone properly. It’s not uncommon for people to mishandle a microphone though, which typically involves them pointing the element away from the direction of their mouths, or just too far to overcome the amount of ambient noise versus their speech. If this is the case, or the presenter is expected to be using their hands to operate other equipment, such as presentation clickers, pointers or a laptop, then a lapel worn microphone would be a better choice.
When a room’s function can vary and audience table arrangement isn’t permanent, the use of wired microphones becomes more difficult to permanently install and maintain. A wireless solution can also benefit a room in which tables are expected to be moved around depending on function or audience size. Wireless microphone transmitters and receivers come in many configurations and can easily expand to cover a large room with multiple presenters, audience seating areas and even room divisions. In the case of a divisible room, there needs to be additional planning for microphone antenna mounting as well as separation of microphones and speakers.
Since large meetings might require an audience to participate with the presenter and even people on the far end of a conference call, or when the audiovisual presentation is being recorded and/or shared with a remote site, it is important that the audio from the source (person speaking) is well above the background noise in the room. Sometimes, the best solution is to have meeting participants instructed beforehand about the meeting etiquette for the room, and they might be expected to participate by using wireless hand held microphones that either require walking up to (like a microphone on a stand), or waiting to be passed one.
While ceiling mics are recommended less frequently, a multipurpose space with movable furniture may require them. If wireless microphones cannot be successfully deployed (which usually requires a person designated to properly place microphones prior to a meeting and collect them for charging after it has ended), this may warrant a case for ceiling microphones. If so, careful attention must be paid to HVAC, noise from fluorescent lighting, room reflectivity (lots of hard surfaces) and distance from microphone to desirable sound sources. Microphones need to be close to participants, and far away from sources of noise and moving air. If air diffusers aren’t spread throughout the room properly and blow too much air directly over seating areas, chances are they will also push air across a microphone element as well, which is difficult, if not impossible to overcome with the audio system’s processing devices.
If the room is large enough that speech audio requires reinforcement to those seated further away from the presenter, consideration must be given as to how that audio is to be reproduced. In rooms that are wider than they are long, a system designed with a pair of loudspeakers in the front of the room may not do a good job of providing audio to everyone. Worse yet, the presenter’s microphone will be subject to feedback given that the microphone’s element has a greater chance of pointing directly at the loudspeaker. A voice lift system in which the presenter’s microphone is gradually introduced into the overhead ceiling speakers, specifically where it is set up to provide greater amounts of speech the further you move away from the presenter is a better solution. At the same time, audience members might be too far from the presenter to effectively be heard during a Q&A session, so it would warrant the case for voice lift to be implemented in the reverse fashion. The same may hold true for a large boardroom table, in which case a similar voice lift solution should be utilized. There are several factors that need to be considered so that microphones meant to cover the audience or opposite table ends are not going to feed back into the system as well.
In the beginning of this article, I mentioned the types of noises that can be heard around a typical office environment. While a building’s designer can do their best to minimize noises from the outside world, the noises inside can be just as problematic. Conversations from outside of offices or conference spaces can distract those inside the room. At the same time, the people on the other side of a closed door are often not expected to hear the discussions taking place inside the room. Even in an open area environment, conversations can collectively add to the distraction of their co-workers. To combat this, specialized speaker systems known as sound masking can add a degree of “noise” to the environment that will make it more difficult to either get distracted by too many conversations or noise from a nearby TV or other sound source, as well as make it difficult for people to eavesdrop. Typically, these speakers are placed above a ceiling grid, or hung from the ceiling deck above and provide an upward (or sometimes downward) full frequency source of white noise that can help cancel out what can be heard in a quieter environment.
Audio Tools & Processors
AV integrators have many tools in their arsenal including measurement devices, software to perform acoustic modeling of a space which predicts how sound will react in a room, and digital signal processors (DSPs) to help them manipulate audio, which can include acoustic echo cancellation (AEC), an important part of conferencing technology. AEC technology stops audio in a conference call from being regenerated by its table microphones and played back through the ceiling speakers.
DSPs can come in many configurations that can handle various functions necessary to accommodate all of the required elements of an audio system. Audio mixers are the most basic of these functions, which provide a way to combine multiple audio inputs including microphones and line level audio sources from various playback devices (computers, Blu-ray players and even telephone lines). Ultimately the goal is to bring these signals to a level that will easily interface with the next downstream device, such as an amplifier for driving loudspeakers, a recording device, a telephone hybrid or a videoconference codec. The number of devices that require connection to the DSP will determine the number of outputs that the processor comes equipped with. Many devices external to the DSP will expect to see various audio configurations, processing and levels of the same audio signal, which is also why they are necessary.
Automatic microphone mixing, which is typically included in a DSP device, can be helpful in combating room noise and side conversations which can distract others on the far end of an audio call. Automatic mixers turn on microphones that detect sound above a certain level and turn them back off when that level falls below a threshold. These devices are best suited for audio and videoconference rooms and provide a valuable way of increasing speech intelligibility in a conferencing system.
Today, many DSP devices also provide a USB encoder/decoder which allows an audio signal to be bi-directionally passed to and from a PC. Many software companies offer some type of communication applications that require direct interaction with the PC’s hardware. Oftentimes, the host PC and DSP device can live together in an equipment rack, but they can also be separated by a distance greater than the allowed USB cable length, as in the case of a laptop at the conference table which is hosting the communication software. When the cable length exceeds the USB recommendation, then an extender must be used to properly pass that audio. However, these differ from the typical HID (mouse/keyboard) extenders and must be certified to work with both the audio device (DSP in this case) and the software which with it is working.
As you can see, achieving proper audio in a room may not always be an easy task, but it is an important one to get right. In a conferencing room, audio must be intelligible for participants to understand and react to the people on the far end of the call. For presentations, clearly hearing the message of the presenter is the goal for all involved; presenter, audience and the person responsible for bridging the two.