Parso is being promoted as an alternative to headphones, creating a personal sound experience while maintaining environment awareness, for use outdoors, while wearing a helmet, or an open office space for online meetings. The user just needs to point Parso at his head, and only he can hear the sound loud and clear.
AFUR is an electronic equipment manufacturing company based in Tokyo, Japan, specializing in connected and wearable devices equipped with various sensors, circuit design, and high-speed signal processing. It carries out contract development up to manufacturing and can flexibly handle small-lot prototypes and mass production.
The highly directional speaker using ultrasonic elements is an evolution of previous designs. AFUR has in fact commercialized an ultrasonic speaker in the past, and Parso is an attempt to create a wireless Bluetooth concept with mass market appeal. "In the past, speakers using ultrasonic waves were not suitable to be wearable due to problems such as size and power consumption, but this problem has been solved by using both structural and electronic circuit approaches," the company states.
"The design of the ultrasonic speaker was fundamentally reviewed, and the approach from each direction of structure and circuit design was adopted. Smaller size and power saving have been achieved, and the speaker itself can be miniaturized. We will release it as the world’s first wearable product for parametric speakers," they add.
The available information for Parso, details a two-stage ultrasonic speaker arrangement. "The biggest problem in downsizing the parametric speaker is the number of elements of the ultrasonic speaker is proportional to the volume, so if you want to increase the volume, you need to increase the area of the elements. This problem was solved by arranging the elements with about 1.6 times the efficiency of laying them on one plane by adding the directivity of ultrasonic waves and making it a two-stage structure."
AFUR also created a single chip solution to drive the system, using a mixed signal controller (mixed digital and analog), to modulate the audio signal onto the drive signal of the ultrasonic element. This allowed significant reductions to the board size, while reducing power consumption by optimizing the signal that drives the ultrasonic element. It also enabled a solution that is able to adapt to changes in the ultrasonic elements.
The Parso speaker can also be charged using a USB Type C connector, allowing portable use with Bluetooth audio. The key to the personal sound area is in the directivity allowed by parametric speakers. Sound has higher directivity as the frequency increases, and conversely diffuses as the frequency decreases. This is why we only hear the bass when standing away or outside a closed live venue.
While "ultrasound" generally refers to sound outside the audible frequency for humans, Parso is a speaker that emits directional sound waves by adding the intended program sound to sounds with frequencies above the audible range, by modulating the drive signal of the ultrasonic element. The result is increased directivity, that allows creating a very restricted listening area, supporting possible applications as an intercom for bikes, as a speaker and microphone for online meetings.
As AFUR notes, the design works as intended outdoors. However, indoors, the directivity is reduced by wall reflections, becoming necessary to absorb sound on the reflective surface to ensure high directivity.
"Parso can be securely worn for walking or running and can also be mounted using a standard 1/4" tripod screw mount," the company says. "Keep whatever you're listening contained to yourself, even while wearing a helmet. With a three hour estimated battery life, Parso can be used in cafes, campsites, and other environments where you want to play music only in a specific area," they add.
Parso will be available for around USD $350 and AFUR plans to produce a limited quantity to be available in May 2022, while remaining open to further enquiries. Further details will be offered to those who sign-up for updates here. Judging from the presentation video, AFUR clearly needs to have input from designers for further applications of the concept.
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