Clive O’Brien is co-owner and CEO of EAV Technology, a Melbourne-based distributor of broadcast and AV equipment. Clive has over 50 years experience in the broadcast and AV industries in Australia and founded EAV Technology over 30 years ago with his wife, Barbara Ward. Clive is passionate about providing innovative solutions to the AV and digital signage market in Australia.

Column: Clive O’Brien

Way back in 1927, The Jazz Singer motion picture stunned the world by synchronising sound with vision… and everything changed. Or did it?

In 2017, we live in a world dominated by visual messages, and digital signage is at the forefront in delivering those messages. But how many times do we see expensive and elaborate video walls, or digital signage in retail outlets where the sound is turned off?

The challenges of combining sound with digital signage are well-known to both AV professionals and end-users alike — noisy environments, privacy issues and focusing your audio so that it doesn’t collide with other audio or disturb other people. So how do we overcome these challenges? How do we engage our audience when we’re competing with a sea of visual messages?

Enter directional speakers: focused sound which can target single or small groups of listeners.


There are several directional speaker technologies currently on the market, and the most intriguing of these would have to be ultrasonic speakers. Evolving from underwater sonar experiments in the 1960s, ultrasonic speakers are now available commercially.

Unlike traditional speakers, which push air, these speakers use ultrasonic sound, comprised of very small wavelengths, normally outside the range of human hearing. The transducer in the speaker modulates the ultrasound signal to change the way it moves through the air, while the properties of the air itself render the ultrasound audible to humans. This results in a highly directional ‘beam’ of sound, just like a spotlight, which can be used to project audio content to a highly-localised area, for example, in front of a digital sign or billboard.

The viewer can hear the audio clearly in the target zone, about 1m wide, whereas others standing just outside of the ultrasonic beam will barely hear anything and, often, will not hear the audio at all.

Conversely, the reflectivity of such a tight audio beam can be used to bounce audio off a screen or another surface, to make the sound appear to originate from that surface.

In either case, the properties of ultrasound produce an ‘in your head’ audio experience for the listener, akin to telepathy. The effect is uniquely engaging and ideally suited to targeted messaging or atmospheric audio.


Line array speakers are another popular technology used for directional or focussed audio. Directional line array speakers are typically comprised of multiple small drivers arranged in a ‘sound bar’ or ceiling tile format.

While not as directional as ultrasonic speakers, they cover a wider dynamic range and use nanosecond signal delay to the outer drivers to deliver a focussed audio ‘sweet spot’ directly in front of the speaker. Outside of the sweet spot, the audio level drops off significantly, to a point where it mixes in with the ambient noise.

They are ideal in noisy environments, such as shopping malls, or airport boarding gates, where you want maximum clarity directly in front of your digital signage, or to create an ‘audio zone’ in front of your display. They also come in a variety of sizes, to complement video walls, single monitor displays or digital kiosks.


Parabolic speakers (often called Sound Domes or Sound Showers) are a unique focussed audio solution for digital signage. Consisting of a stereo driver projecting audio into an open acrylic dome, they are reminiscent of the Cone of Silence in the TV series Get Smart, or a prop from a 1950s science fiction movie.

The sound is reflected by the dome and concentrated in a defined area underneath the speaker. Parabolic speakers can localise sound to either a single or small group of listeners, with minimal audio bleed beyond the width of the dome itself. As well as providing focussed audio output for digital signage, kiosks and POS displays, parabolic speakers have the additional advantage of an eye-catching design, while giving the viewer a visual cue as to where to experience the audio for the display.


Whichever directional audio solution you choose, there’s no doubting the effectiveness of using directional audio in your digital signage installation. Your digital signage delivers a targeted message, but if you don’t have targeted sound to capture your audience and convey that message, they may be missing out on half the picture. With directional speakers completing the picture, the future of digital signage is sound.

Clive O’Brien can be reached at