In today's hybrid business environment, meeting attendees are not typically sitting in the same space. Participants are located in multiple geographical locations, thus meeting spaces require video conferencing capabilities so the in-room and remote participants can collaborate together. The remote participants should have the same level of engagement and satisfaction as being in person.
But did you know the two most common pain points are audio related? First is poor microphone pickup for the remote participants listening into the space, and the second being poor loudspeaker-quality for the in-room participants so they can properly hear the remote participants when they are talking. If the participants can't understand what's being said, no video or screen sharing is going to recover the meeting. Everyone participating needs to be clearly heard and understood. This is known in acoustics as speech intelligibility: the frequency range of human speech and its comprehension by the human ear. For IT managers and meeting leaders alike, a basic understanding of a few key acoustical principles helps make meetings successful. Here, we break down the most common acoustics challenges as well as some techniques that can help fix them.
Sound and microphones behave remarkably similarly to light, and it's helpful to use light to visually explain how sound interacts with various types of spaces and environments. For instance, light, sound, and microphones are reflected by certain types of surfaces — in light's case, by highly polished surfaces such as mirrors, which can result in glare; and in sound and microphone's case, by hard, rigid surfaces such as glass, tile, or wood, which cause various types of echoes that can impact speech intelligibility.
There are similar dynamics when it comes to rough or uneven surfaces, which can either absorb or diffuse both light and sound. And those reactions — reflection, critical distance, absorption, and diffusion — are the key dynamics to keep in mind while evaluating a particular meeting venue for potential acoustical problems.
Critical distance refers to the distance between the person talking and the point in the room where the room reflections interfere with their direct voice, which reduces listening comprehension (these room reflections can seem just as loud as the original person talking). This is the critical distance point. At this point, speech intelligibility greatly decreases, especially for the remote participants getting their audio from a microphone in the room. In spaces with hard surfaces, the critical distance usually begins halfway into the room and extends beyond.
As mentioned, room reflections are a common problem, mainly because they're caused by the fundamental structural elements of any room: walls, floor, and ceiling. For instance, many large conference spaces can have drywall ceilings, glass walls, and concrete floors. These solid materials cause sound waves to bounce off or between them. These reflections will mingle to form reverberations ("reverb" for short). Additionally, when reflective surfaces are at several different angles in the same space, that complex geometry can cause variations in the reverb time depending on the direction of the sound source.
The easiest remedy to stay within critical distance and combat room reflections is to keep the in-room participants within a total of 10 feet, and to use a microphone with directivity for the in-room audio pickup to the remote participants. Today, there are conferencing devices like the Bose Professional Videobar VB1 that includes beam-forming microphone arrays that track people talking in the room and remove echoes coming from reflections even up to a distance of 20 feet (6 meters).
For meeting spaces with high ceilings or deeper than 16 feet or 5 meters, absorption material are used as an acoustical remedy for overly reflective spaces. Carpeting is a primary treatment for larger venues such as theaters and concert halls — and it serves that same purpose for large meeting rooms. Other types of absorptive treatments include drapes and curtains, but there are also professional solutions available for this. The most common type is acoustical panels, which are designed to absorb sonic energy in particular frequency ranges. Typically, one- to two-inch thicknesses of foam-type panels are appropriate for absorption in 500-Hz to 4-kHz range, where most speech-based reflection will occur. They are mounted most often on walls but may need to be placed on ceilings depending on the layout of the space. If there are other broadband sound sources in the room — a presentation accompanied by music, for instance — a wider frequency range needs to be addressed with additional thicker panels up to about three inches.
Diffusion isn't quite as straightforward as absorption, but it's a technique that can be useful in certain circumstances. Essentially, diffusion breaks up sonic energy as opposed to soaking it up. This can help keep the volume level of speech and other presentation elements at a sufficient level without adding more electro-acoustical volume (i.e. turning up the PA system higher and risking distortion). For example, imagine spilled water on a wooden-slatted floor. The spaces between the slats will diffuse the liquid over a wider area than if it stayed in one spot — it's the same amount of water but less concentrated.
Diffusors come in a variety of shapes, but the most common are small squares arranged in a pattern on a panel, rounded or cylindrical columns, and panels. These are generally positioned vertically on walls. As with other acoustical treatments, specific sizes and shapes correlate with specific frequency bands — but for typical meeting room applications, there are ready-made solutions available.
There are also more active solutions available, including Bose Professional's EdgeMax EM180 loudspeaker. Its waveguide, which manages the directional propagation of sound energy, keeps that energy off of reflective surfaces such as walls or windows and can lessen the need for passive acoustical treatments like absorption panels. Similarly, VB1 utilizes beam-forming microphone array technology as mentioned earlier and our renowned proprietary loudspeaker transducers that reproduce accurate, room-filling audio at lower volume levels, thus helping avoid acoustical issues.
Marshall McLuhan famously proclaimed that "the medium is the message." For meetings, the meeting space is part of the meeting experience. Proper acoustical treatments and techniques can make a world of difference in how well a meeting's message is communicated and the overall enjoyment of the experience.