Voice lift: Now hear this

Meetings can be stressful enough without the pressure of not being able to hear what is said. Paul Skelton listens to the experts.

Written by Paul Skelton

What’s the point of holding a meeting if some people can’t hear the discussion? If people have to strain to listen to a speaker, they will quickly lose interest or suffer ‘audio fatigue’. Voice lift is a technology – series of technologies – that aims to take the stress out of meetings by making it seem as though the presenter is sitting right next to you.

Tackling audio fatigue

Timothy Mackie is senior field systems engineer with Yamaha Unified Communications;

“Audio fatigue is the number one problem to avoid in any meeting,” he says. “Intelligible audio is paramount for productive stress-free meetings, and correctly executed voice lift applications achieve this. The objective of voice lift is to achieve the same comfortable speech volume levels throughout the room or space. This allows for those far away from a person talking to hear at the same level as someone right next to the person.”

Jason Grbevski is the product channel manager, integrated systems, for Sennheiser. He says the proliferation of meeting and collaboration spaces in enterprises has led to voice lift systems becoming more common.

“Voice lift systems can take many forms, yet their essential purpose is to augment the natural loss of speech in a larger space. This is not to be confused with public address systems, which broadcast at high volume to cover large areas.”

Voice lift equipment typically includes microphones, a digital signal processor (DSP) to mix and route the microphone audio, an amplifier (multi-zone amplifier for larger rooms that require balancing the audio in different areas) and loudspeakers.

“Multi-zone amplifiers are advantageous because they allow fine-tuning of volume levels based on zones,” Jason says.

Some zones might require a bit more voice lift than other zones or areas of the room or space. Perhaps +3dB in one zone and +5dB in another.

“There are more complex types of voice lift, such as ‘mix minus’, which routes specific microphones to specific loudspeakers. In conventional voice lift, all microphones are routed to all loudspeakers. Ultimately, voice lift is an application of multiple technologies, rather than a technology in itself. Its purpose is to provide amplification of dialogue in a conference or discussion environment where natural speech suffers losses due to distance or a floor creating high room noise.

“This affects intelligibility and ultimately induces fatigue during longer sessions, much in the same way as eye strain if you cannot see the blackboard from the back of the classroom.”

Lifting our meetings ‘out of the box’

Sennheiser’s ADN delegate conference system is an example of implementing voice lift in a complete ‘out of the box’ solution. It is designed for more formal delegate-style meetings. Microphone, signal processing, amplification, and loudspeakers come in a single delegate station form.

“Sennheiser’s expertise in high-quality transducer design allowed us to create microphones voiced for excellent speech intelligibility in voice lift applications,” Jason says “Their ‘gain before feedback’ characteristics are particularly important, considering that many of these systems are used with ceiling speakers directly firing into the capsules.”

The SpeechLine range of products was engineered for these environments.

“Voice lift is just that – lift. It is not designed to behave like a sound reinforcement system or a large public address system. A voice lift system should feel natural in the way it represents the talker’s voice. The participants should not struggle to hear each other’s voice, nor should it boom through the room.”

“A correctly deployed voice lift system should result in the perception of little to no amplification, but the difference is easily noticed when amplification is removed. Ideally, a voice lift system will permit zoning of the loudspeakers in the space. This allows for the talker’s amplified signal to be progressively increased in zones farther from the microphone.

“This helps maintain natural support for the dialogue and offers a better resolution in offsetting the losses over distance. You will often see ‘mix-minus’ systems employed in these scenarios, as they provide greater control of which microphone signal can be reproduced by each loudspeaker zone. They are extremely effective, but they can be more expensive to implement.”

Factors to consider when implementing

Timothy says that size, acoustics, audience members and the number of active participants are factors that can determine the voice lift needs of a space. Background noise also has an effect.

“The best voice lift applications use directional microphones close to the people speaking and the correct number of loudspeakers to achieve complete and even room coverage. You can also use a multi-zone amplifier to allow different volume levels to different loudspeakers or groups of loudspeakers.

“Room size and shape play a major role in the number of components needed for good voice lift and highly intelligible audio.”

Yamaha’s Executive Elite wireless Microphone system has wearable, gooseneck and tabletop microphone options that can be mixed and matched to suit user preference and the application.

“It’s a proven solution for implementing voice lift and providing voice comprehension in large rooms or spaces,” Timothy says. “The system can support up to 44 microphones and is loaded with audio-enhancing technology, including Designed for Speech technology, built-in equalisation options and advances such as an improved signal-to-noise ratio to provide meeting participants with a best-in-class experience.”

Yamaha also produces intelligent ‘power over Ethernet’, Dante-enabled line array loudspeakers.

“Voice lift will always need to be calibrated or set up based on the previously mentioned parameters,” Timothy says “An integrator will set the volume levels based on microphone and loudspeaker placement relative to participants in the room. The integrator will take sound-level readings throughout the space and adjust the loudspeaker levels accordingly.

“Again, the overall effect is to have similar, comfortable volume levels throughout.”

Jason says truly ‘out of the box’ solutions are rare.

“The exception to this is discussion systems, like Sennheiser’s ADN platform. These are stand-alone platforms that incorporate microphone, signal processing, amplification and loudspeakers into a single station that can be easily scaled. Delegates require their own station in front of them that captures dialogue and manages playback of other meeting participants via the integrated loudspeakers. These systems are very flexible and help to bring structure and formality to meetings.”

Knowing your space

“Parliamentary or council chambers would be the easiest scenario for the installation of this type of system. Yet in a corporate environment, the form factor of a discussion system is not as visually appealing. This is where a mix-minus system is usually the implementation of choice.

“These more bespoke, integrated solutions require a clear understanding of the room layout to determine the placement of loudspeakers in relation to microphones.”

An understanding of how the room will be used is essential when determining placement and coverage.

“System gain structure is probably the most important factor when commissioning such a system,” Jason says. “Microphone gain is important in ensuring that the automatic mic mixer responds effectively to manage the number or gain applied to open microphones, reducing the risk of acoustic feedback being induced into the system.

“This also ensures that loudspeaker zones can be commissioned with progressive amounts of microphone gain to adjacent zones.”

However, not every conference room needs voice lift.

“Each room should be evaluated based on size, number of participants, acoustics, etc,” Timothy says.“A simple and quick way of gauging whether a room needs voice lift is to have participants populate a room and ask those farthest away from each other to try having a conversation. Distance or room size is the main consideration.”

Jason agrees, saying another way of assessing requirements is that if he cannot clearly hear someone from across the table, then a voice lift system could add value.

“In smaller rooms where unamplified dialogue flows freely there is no appreciable benefit in a voice lift system.”

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