At Chirp, we’re constantly researching and testing ways to improve data-over-sound as a means for data transmission. Recently, our research and development team was able to successfully produce a data rate above 2kbps within the near ultrasonic band only, over the air, using consumer hardware.
Below, Haris, our Research Engineer, and resident telecommunications guru, provides a demonstration and explanation of this high data rate transmission:
“In transmission over sound, we can combine audio with digital communication techniques to exploit a fast and easy-to-deploy peer-to-peer communications system for smartphones and laptops. The spectral edge of the speakers and microphones of these devices at the ultrasonic range serve as an ideal inaudible medium for data-over-sound transmission.
First, we take into account the specific characteristics of the mics and speakers in the system’s design in this range. Second, we assess background noise to determine what frequencies are present in the environment. With very low background noise, there is no interference, and, by applying signal processing and digital communication techniques, we can achieve very high data rates.
In the following video, we have set both the smartphone and laptop in airplane mode, while using the smartphone as a transmitter of data-over-sound at the ultrasonic range. We send one message composed of random integers with 30 bytes (240 bits) of useful information.
Once the message is sent, it then appears in hex on the smartphone screen. The laptop serves as the receiver (or decoder, to be specific) of the system. Once the message is decoded, the message is also shown on the laptop screen. The data rate achieved is over 2.5kbps. This is twice the nearest data rate that has been reported for over-the-air near-ultrasonic transmission using a smartphone.” – Haris Kourogiorgas, Research Engineer, Chirp
*This post has been updated since original publication.