Targeted Audio Transforming Digital Signage

Most digital signage is completely silent. The reason is fairly simple. While you can avoid the visual portion of a presentation by turning your head, you can’t avoid the audio as easily. "Where video tends to be focused into a vector, sound tends to be a 360-degree bubble around you," explains Dick Trask, marketing director for Scala, Inc.

"Repetitive noise is a huge issue with employees," says Ed Glicken, director of foreign sales for Brown Innovations. "We became involved in a lot of kiosk applications early on as a direct result of employees turning off or actually damaging equipment because of the repetitive noise."

The repetitive noise issue could disappear completely because of a new generation of speakers that focus sound into a narrow beam. The Audio Spotlight from Holosonic Research Labs, for example, confines its sound within a tight band- just three to five degrees across. As you move outside the audio beam, there’s a sharp decline in the volume. "One step will be 90 percent of the sound level- it drops like a rock," says F. Joseph Pompei, Holosonic’s founder. "We’ve had installations where three people can stand shoulder to shoulder and hear completely different soundtracks."

Focused speakers really come into their own when combined with a motion sensor or other triggering device. "We did a project in New York in about 50 locations- bookstores, coffee shops and other places like that- where we had a triggering system that would whisper at you as you walked by a display for Court TV," says Pompei. "It would whisper,‘Excuse me, have you ever thought about murder?’ It was a creepy message that really got the point across. The point was to do something clever and unusual as they were walking through a quiet space."

Motion sensors also trigger focused audio in London’s popular Churchill Museum, a permanent installation within the underground Cabinet War Rooms where Churchill and his War Cabinet commanded British forces during World War II at the height of the German Blitzkrieg on the city. Among the exhibits relating to Winston Churchill’s political career is a "speech wall" capped with a series of directional speakers aimed down from the ceiling. "We fitted a reflector on the floor under glass and a sensor next to them," says Rob Ferguson, a design manager with Electrosonic Systems. "As you walk under the directional audio, it triggers our MP3 players back in the control room. It gives you a monologue about each of the pictures you see in front of you."

Because the audio commentaries are triggered via sensors, visitors hear each audio clip from the beginning. "We have a display about every six feet along the wall," says Brian Hinckley, business manager of Electrosonic Systems’ Managed Media Services Group. "You can walk from one display to the next and get a personalized tour that’s completely unobtrusive relative to the other displays."

For the speech wall, Ferguson chose American Technology Corporation’s (ATC) HyperSonic Sound speakers. He was impressed with their extreme directionality. "We did some tests where we took a speaker down and aimed it across the room," he explains. "People could hear it from one end of the room to the other. It must have been a 20-meter-long area." He wasn’t as impressed with the speakers’ frequency range. "It’s really just suited to voice. It’s not full range by any stretch of the imagination."

Hinckley cautions that you need to understand the limitations of the technology and manage the expectations of your client. "If the client wants to stand under here and think it’s going to sound like a studio- quality or full-range speaker, then he or she is going to be let down," he says. "At the same time, whoever is creating the audio track needs to be aware of the particular model. If we’re creating custom content, we often provide a similar speaker so we can understand what it sounds like in the studio. We tune it to the appropriate frequencies and try to limit the low end. We essentially EQ the soundtrack to that particular box in order to maximize the focused sound performance."

ATC has sold its HyperSonic speakers to a wide range of commercial, government and military installations. The complete system combines an ultrasonic powered emitter (directional speaker) and proprietary signal processor/amplifier. In addition to generating a cone of sound targeted to one or two listeners, you can use HyperSonic speakers to communicate intelligible messages over long distances or move sounds around a room in real time.

With new audio capabilities comes the freedom to create different forms of content. "Everyone is learning what the content would be," explains James Croft, ATC’s chief technology officer. "Is this content people will want to hear? Is it something more people are going to enjoy? Or is it something only someone in one spot is going to be interested in?"

In a grocery store, for example, a 42-inch screen over the vegetable section might require a wider audio beam so groups of customers can hear the audio simultaneously. In that same store’s checkout line, however, the audio might be targeted to one person and last only as long as it takes to remain in that position in line. "Usually you’re either trying to cover an area that’s equivalent to what the video screen coverage is, or you’re trying to limit the area to a very narrow area so that only someone in a very specific spot hears it," says Croft.

Focused audio often has to reconcile competing interests, especially at retail. "You have the advertisers who demand that their message be heard," says Glicken. "Otherwise, they’re not going to pay. And you have the retail environment that the signage is going into that says we can’t bother our employees, and we don’t want it to bother our customers who are not in viewing range. The digital signage company is stuck in the middle, where it can’t be too loud for the store and it can’t be too soft for the advertiser."

Glicken’s employer, Brown Innovations, sells two types of directional speakers, each suited to a different purpose. The downward-pointing Sound Dome provides a tight audio beam with a 5-to-1 isolation ratio. "That means within the sweet spot, it’s going to be five times as loud as the bleed just outside," he says. "If you tune it so that the bleed is lower than the ambient noise, a person outside isn’t going to hear it." The Sound Dome is well-suited for applications where you know exactly where the person will be standing, such as at a touch screen. The side-pointing Maestro, on the other hand, offers a somewhat wider audio beam. It would be a good choice for creating an audio space for a 42-inch screen. "You want to create an area in front of the screen where anyone who is aware of the screen will hear the associated audio," he explains.

The Maestro also features an automatic audio gain. "It uses a microphone to monitor the environment, and it will raise and lower the volume of the speaker as the ambient environment changes," says Glicken. "In a lot of environments, there can be a 30 to 40 dB swing throughout the day as crowds come and go. This will keep it at the same relative comfort level no matter what is going on." You could mount a Maestro underneath the monitor or install it flush into a wall or cabinet.

Finland-based Panphonics takes a similar two-pronged approach with its focused speakers. The Sound Shower is usually mounted in the ceiling to provide a highly directional audio footprint underneath. It’s available in a variety of sizes, ranging from 600 by 600 millimeters to 3000 by 200 millimeters. The Sound Sign is typically mounted on the same wall as the screen. It’s designed for digital signage applications where you want to maintain an audio corridor around the screen, but don’t want to annoy the employees. Like the Maestro, it has an automatic ambient volume control so the audio won’t be drowned out during periods of extreme activity.

Whether you should even consider audio or not will depend largely on the installation’s environment. "If you’re in a noisy train station, and you’re displaying the train schedule, you might not use audio because you’re competing with the ambient noise around you," says Trask. "Or you might not use audio in a digital signage application where you don’t have an audience that’s there for any longer than a few seconds. They’re on an escalator, in an elevator or walking down an aisle. However, if you’re standing in line waiting for the next ATM machine or your next hamburger, audio might be an option because you have a captured audience."

What’s the best approach if you have an audio-friendly environment? Use sound sparingly to generate an initial curiosity and draw the viewer in for the visual content. "The eyes tend to follow the ears," says Croft. "You hear a sound behind you and then turn to look at it. Whereas if there’s a visual element behind you, it may be out of your field of vision, so you may not notice it." Just as TV advertisers have learned to emphasize the audio message visually because viewers prefer to mute the volume during the commercials, digital signage will likely remain a mostly visual medium. "Communicating visually is the heart and soul of what digital signage is all about," says Trask. "It’s all about the content. If the content isn’t delivering the message on its own, then the sound isn’t going to help you."

American Technology Corp. www.atcsd.com
Brown Innovations www.browninnovations.com
Electrosonic Systems www.electrosonic.com
Holosonic Research Labs www.holosonics.com
Panphonics www.panphonics.com
Scala, Inc. www.scala.com