Radio Frequencies & Audio Frequencies
In a previous post we looked at the physics of sound — how it is made and how it travels. In this post we will compare how audio and radio technologies operate in their respective domains and the different kinds of technologies which operate along each of these spectra.
Radio Frequencies
Most of the wireless networking technologies that we are familiar with, such as Wifi & Bluetooth, use a (relatively) narrow range of frequencies on the electromagnetic spectrum as their medium — this range is termed ‘Radio Frequency’ or simply ‘RF’. This portion of the spectrum allows for an exceptionally wide of range different examples of RF networking and communications. Everything from cordless phones, AM/FM radio broadcast, communicating with deep space satellites, NFC, walkie-talkies.
More narrowly, the band restricted by governments and regulators for use in Industrial, Scientific and Medical uses (ISM Band) includes most of the technologies discussed here. Each of these technologies and protocols have to share the same space along the electromagnetic spectrum, either for practical/physical reasons, adherence to international standards or governmental regulation. Both WiFi and Bluetooth primarily use frequencies around 2.4GHz, with more modern WiFi devices also taking advantage of a less congested region around 5GHz.
RF technologies are great for creating high-bandwidth secure networks, whilst allow each node (device) to remain free from cables. Most require authentication or some kind of identification step before a connection is made and access to network resources given i.e Logging in to WiFi, or pairing via Bluetooth. Some, like BLE beacons, can be interacted with without prior setup.
Sound Frequencies
As we discussed in a recent post, sound is the vibration of particles (usually in air) at different frequencies which together produce a wave which travels out from the source of the vibration. The frequency of vibration sits on a completely different spectrum to the RF technologies we have been discussing above.
Sound has long been used as a means for sending data. We use sound to convey information every day using speech. Human to human communication using sound also includes examples like Morse code.
In the animal kingdom, to give just a few examples: spiders use sound to ‘listen’ for prey falling into their webs; elephants use very low frequency sound to communicate for hundreds of miles across the savannah; birds use it to call to each other and millions of other species in order to convey information as well as receive it.
In the machine to machine realm, sound was used by dial-up modems in the earliest examples of networked computers. Just like with RF technologies, there are various different schemes and standards for transmitting data using sound, and some use different frequency bands (Chirp, for example has products which separately use audible and inaudible, ultrasonic portions of the sonic frequency range).
How do these compare?
This depends on several factors, though it should be noted from the start that all of these technologies can be used alone or as part of a combined system which leverages the benefits of each separately. These technologies sit alongside each other and can act collaboratively, rather than competitively.
Technologies such as WiFi, Bluetooth and Chirp’s data-over-sound can sit alongside each other as complementary technologies, each with particular affordances and benefits for certain use cases.
- Bandwidth : Compared to most modern RF technologies, sound can carry much less data, so if ultimate bandwidth is the priority sound may not be the right fit. RF technologies are typically orders of magnitude faster than comparable data-over-sound transfers.
- Hardware : Sound is everywhere around us, and billions of devices are able to make or listen for sound via their microphones and loudspeakers. This makes sound a good fit if you need the widest possible reach.
- Broadcast : Sound is (most of the time) practically omnidirectional, meaning it is broadcast from a source and travels out in all directions from its origin. This makes it particularly well suited for broadcasting data in a ‘one to many’ network configuration to devices which may have no prior interaction or association.
- RF-sensitivity : Certain applications are extremely sensitive to radio frequency energies — especially in industrial, security or scientific areas. Sound can act in these areas without issue.
- Connectivity : Sound works completely peer-to-peer, meaning no additional connections are needed to ‘the cloud’ or other network services, so it works great in situation where there is no other network access.
As a complementary technology, data-over-sound represents a compelling addition alongside RF networking standards because of several key characteristics: It is simple, ubiquitous and extremely portable.
Our next post in this series will take a deeper look at the different ways in which data can be sent using sound and the benefits and limitations of each method.
To find out more about Chirp’s data-over-sound solutions, please visit us at Chirp.io or get in touch contact@chirp.io.
