Each month we’ll deliver highlights of intriguing new exhibit and event marketing technology and highlight new interactive projects in the event marketing space. Bringing to you the latest emerging technologies from the worlds of media, events, trade show environments, exhibits, retail, art, technology, material research, and cross-platform experimentation. Click here to download our latest Interactives White Paper.
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Joe Cantrell Interactive Technologist
Hyperdirectional Speakers - what are they and how do they work?
Imagine you are at a trade show and a specific exhibit catches your eye. You walk up to the installation and you perceive audio content that you could not hear until you were right in front of the exhibit. As you move away, the sound also disappears as if by magic.
This experience is the hallmark of hyperdirectional speaker technology. This technology transmits sound to specific points in space while inaudible elsewhere. How does this technology work and how does it differ from traditional speakers?
Traditional speakers commonly work using a paper cone attached to an electromagnet. This electromagnet is excited by electrical signals from an amplifier. When the signal is polarized positively, it moves the speaker outward, and likewise when a negative current is applied, the speaker moves inward. When this happens in rapid succession, it produces movement in the air, which we hear as sound. Sound produced using this method is broadcastin a wide array. That is, it sends sound out in nearly all directions at once, filling the entire room with sound.
Hyperdirectional speakers function in a drastically different manner. They use a process called acoustic heterodyning to create audible sound. This process exploits the limitations of human hearing to pinpoint audio in space.
It works like this: Hyperdirectional speakers have two speaker elements that emit frequencies above the range of human hearing. The magic happens when these frequencies are slightly different. When two sounds that individually are above human hearing range but different from each other are pointed at an object, the difference between them is audible. For example, if one speaker element is projecting a frequency of 30,000hz and the other is creating a 35,000hz tone (both above the range of human hearing) the difference between them (a 5,000hz tone) is created, which is within the range of human hearing. High frequencies tend be directional. That is, the higher the pitch of a sound, the more easy it is to detect where the sound came from.
In hyperdirectional speakers, the extremely high frequencies used create the illusion of the sound emanating from the point of difference between the signals. In other words, we hear the sound not ascoming from the speaker itself, but from where the speakers are aimed.
This effect is striking, but also limited. The sounds produced tend to be noticeably quieter from conventional speakers and bass frequencies are virtually nonexistent. That said, they are quite useful for isolating multiple spoken word or similar audio content in a limited space without intruding on each other.
Popular manufacturers include Brown innovations and Holosonics.