Voice Lift Takes Communication to a New Level
The most critical aspect of a meeting is interaction – the give-and-take between co-workers, students and instructors, board members, etc. While videoconferencing systems are designed to enable interactivity between participants at different locations, their importance to communication between people in the same room is often overlooked. Conventional sound systems enable the audience to hear the presenter or instructor, but they don’t do anything to help audience members to hear each other.
Speech level naturally fades as the distance between the talker and the listener increases. In typical rooms, the middle and high frequencies – which carry consonant sounds and are thus critical to intelligibility -- tend to be the first to get lost in the muddle of background noise and sonic reflections. The impact is made even worse when people face the front of the room instead of each other (such as in a training room), since the most important speech frequencies travel mostly forward from the speaker’s mouth. But even where people are facing each other, a person seated at one end of the room may not be able to hear someone at the other end without straining. Worst of all, they may not complain about the situation because they assume that they’re the only one who can’t hear clearly.
The Solution: Voice Lift
The solution is a special type of sound system called voice lift. A voice lift system amplifies the voices of people in one part of the room just enough so that people in other parts of the room can hear them clearly. Unlike a conventional sound reinforcement system, a voice lift system bolsters only those frequency ranges that are most critical for intelligibility, and only enough to restore the loss caused by the distance between the farthest talker and listener in the room. Voice lift usually increases the speech level in the room by 3 to 6 dB at the most. The effect is so subtle that many users don’t even realize there is a sound system until it is turned off.
How Voice Lift Works
A typical voice lift system is similar to a conventional sound reinforcement system, in that it consists of microphones, digital signal processors, amplifiers, and loudspeakers. The key difference is that the room is divided into zones, and the microphones in one zone are only connected to the loudspeakers in the other zones.
While it’s possible to use standard table microphones with a voice lift system, ceiling microphones are almost always preferred. But two things are critical: First, the microphones must have an extremely tight polar pattern so they do not pick up the sound coming from the loudspeakers, which would cause feedback and render the voice lift system useless. Second, the pickup area of each microphone must be able to be accurately aimed so that it picks up the desired group of people. Common omnidirectional or cardioid microphones on the ceiling can’t deliver sufficient speech enhancement without feedback, and even most array microphones fall short. This makes the Microflex® Advance™ MXA910 ceiling array microphone a particularly useful tool. The pickup lobes of the MXA910 are extremely directional – even narrower than a shotgun microphone. The width and position of each lobe can be easily adjusted to precisely match the desired coverage area. This allows the MXA910 to outperform any other ceiling microphone solution in voice lift applications, with more consistent speech levels throughout the room and greater gain before feedback. The MXA910 can also deliver 9 dB more voice lift than conventional microphones in a typical application.
Voice lift restores the natural speech level of the talker evenly throughout the room, just enough so audience members can hear each other clearly without straining.
When is Voice Lift Appropriate?
Voice lift is appropriate in rooms that are large enough to make it difficult for participants at opposite ends of the room to hear each other without straining. A minimum room size of 40 feet by 40 feet, with at least 25 feet between talker and listener, is a good starting point. If it is difficult for people to hear each other in a room smaller than this, it is more likely that acoustic treatment is needed to solve issues such as excessive noise from air handling, hallway traffic, electronic equipment and the like. In theory, there’s no limit to the size of the room in which a voice lift system can be installed; ceiling height will have more of an effect than room size on the success of the system. In most cases the ceiling microphones are mounted between 8 feet and 12 feet above the floor; higher installations are possible but will depend on the room acoustics.
Voice lift is useful in a number of applications and environments, particularly where the conversation is interactive and multi-directional, involving students or audience members in addition to a primary instructor or presenter at the front of the room. In training rooms, lecture halls, and even large meeting rooms, voice lift makes it easier for a person in any part of the room to be heard evenly throughout the room.
“…When a voice lift system is properly set up the communication is so natural that the participants will not know it is on, until you turn it off.”
Forcing people to move to a stand microphone or wait for a microphone to be brought to them creates awkward delays that stifle interactivity. Voice lift systems allow the conversation to flow smoothly and effortlessly. Everyone involved can talk, move, and interact naturally, without having to think about the technology in the room.
Control and Configuration
With many spaces now configured for a variety of uses, it’s important for a voice lift system to be easily controllable so it can be used when it really provides a benefit. During video conferences or when people are collaborating in small groups the voice lift system is likely not needed. When it’s time for groups in the room to share their ideas, voice lift can be turned on so every group can hear each other. This is made simple by the MXA910’s ability to assign and recall templates with specific microphone lobe configurations. With a simple selection on the room control system, the microphones will be correctly configured when the room is divided or combined, used for a simple presentation, or set up for an interactive training session. The voice lift configuration can be activated only when it’s needed.
It is important to choose a system integrator who has experience with voice lift systems and allow for necessary adjustments in the commissioning time. An experienced installer will start by equalizing the loudspeakers to optimize them for the room, which is important to ensure that the system is stable and will deliver the expected speech level in each zone.
A correctly installed voice lift system should only make subtle changes to a room; when set up correctly, many people won’t even know that the system is on. When it’s turned off, however, they’ll realize there was something helping them to understand conversation. That’s the power of an effective voice lift system – it makes the whole communication experience more natural. A voice lift system including the MXA910 takes this to the next level, offering a multi-purpose audio solution that improves participants’ ability to hear, understand and interact in a cost-effective and easy to configure setup.
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To hear what users have to say about voice lift, watch the videos below: