RadioSonic(TM): A Preview of a Teaching Platform Using Audio-Frequency Waveforms

RadioSonic is a new educational platform under development that uses real-time audio propagation to emulate wireless channel behavior for hands-on SDR instruction. By shifting RF waveform experimentation into the acoustic domain, the RadioSonic platform enables exploration of realistic multipath, Doppler, digital modulation, and other physical-layer effects using affordable purpose-built hardware, at a fraction of the cost of equivalent RF hardware when scaled to the speed of light.

This talk provides a first look at the platform’s architecture and draft curriculum materials. The underlying concept of scaling the speed of light to the speed of sound on low-cost devices for real-time RF emulation is patent pending and being developed to support SDR and DSP education in environments where cost, licensing, and RF complexity present barriers to learning.

The presentation will illustrate how the platform can be used for hands-on implementation of digital filtering, timing and carrier recovery, and modern modulations such as QAM and OFDM, as well as spatial techniques including diversity, beam steering and MIMO, using wavelength-consistent waveforms that reflect real-world channel effects at audio scale in real-time hardware.

Targeted for release in Spring 2026, the RadioSonic platform will include extensible software released under a permissive license and designed around common interfaces to simplify integration and modification. These design choices are intended to encourage collaboration and future community-developed functionality as the platform matures. Attendees will preview the platform’s direction and have an opportunity to provide feedback to help shape its relevance to the signal processing community.

What this presentation is about and why it matters

Dan Boschen introduces RadioSonic, a low-cost teaching platform that emulates RF wireless behavior by running RF-like waveforms in the audio band. The idea is simple but powerful: scale the propagation speed of electromagnetic waves (the speed of light) down to the speed of sound so that wavelength-dependent RF phenomena — multipath, Doppler, coherent fading, and the baseband DSP used to deal with them — appear in slow motion and are affordable to build and use in a lab. For engineers and instructors, this matters because it lowers the cost, licensing and safety barriers of hands-on RF experiments while preserving many of the signal-processing lessons learned from real wireless systems (carrier recovery, timing, OFDM, MIMO, etc.).

Who will benefit the most from this presentation

This talk is targeted at DSP and communications educators, graduate and advanced undergraduate students, and engineers who teach, learn, or prototype software-defined radio concepts. It is especially useful for anyone who wants hands-on labs for: introductory DSP and filtering, carrier and timing recovery, equalization, OFDM and modern modulations, and simple spatial techniques (diversity and small-scale MIMO) without buying expensive RF test gear or dealing with RF regulatory issues.

What you need to know

To get the most from the talk, you should be comfortable with the following core concepts and how they apply to both RF and audio implementations:

• Sampling and Nyquist: Analog-to-digital and digital-to-analog conversion rates set the usable bandwidth. In RadioSonic, RF channel bandwidths are scaled down into audio bandwidths that fit common audio ADC/DAC rates.
• Complex baseband and digital downconversion (DDC): Typical SDR chains mix a bandpass RF signal down to complex baseband using an NCO and perform filtering/decimation. The same steps occur in RadioSonic but at audio-rate frequencies. A useful relation is the frequency scaling used to map RF to audio: \(f_{audio} = f_{rf}\times\frac{v_{sound}}{c}\), where \(v_{sound}\) is sound speed and \(c\) is light speed.
• Rate conversion and multirate filters: Implementations use CIC filters, FIR shaping, and decimators/interpolators — exactly the algorithms you study for SDR, but operating at much lower rates on low-cost MCUs.
• Channel effects and wavelength consistency: Multipath delay spreads and frequency-selective fading depend on wavelength. By scaling frequencies and preserving wavelength relationships, the audio channel reproduces many RF-like fading patterns (walls and large surfaces produce similar reflections), though small-object scattering and Doppler scale differently.
• Real-time streaming and DMA: The platform streams samples via ping-pong DMA buffers at the ADC/DAC level so lessons can be inserted either sample-by-sample or in blocks for real-time processing.
• Practical constraints to watch for: coherence time at audio speeds, oscillator phase noise, microphone/speaker placement relative to scaled wavelengths, and the dynamic range/bandwidth of the audio codec (the presenter mentions 24-bit ADCs/DACs and dual channels as target hardware).

Quick tips for watching

Listen for how the presenter maps specific RF examples (e.g., a Wi‑Fi 7 packet) into audio, what processing blocks are reused from SDR practice (NCO, mixers, CIC, shaping filters), and the hardware/firmware choices (ESP32, codecs, DMA). Note the caveats he raises about what does and does not scale perfectly (Doppler and small-object scattering), since those affect which experiments map well to audio.

Glossary

• Software-defined radio (SDR): A radio architecture where signal processing that would traditionally be done in analog RF is implemented in software or firmware.
• Digital downconverter (DDC): DSP block that mixes, filters, and decimates a passband signal to produce complex baseband samples.
• Numerically controlled oscillator (NCO): A digital sine/cosine generator used to mix signals to/from baseband.
• CIC filter: A class of efficient decimation/interpolation filters used in multirate systems.
• Complex baseband: Representation of an RF signal as I (in-phase) and Q (quadrature) components centered at zero frequency.
• Multipath / frequency-selective fading: Channel behavior where delayed copies of the signal interfere, producing notches and ripples across frequency.
• OFDM: Orthogonal frequency-division multiplexing — a multi-carrier modulation that turns a frequency-selective channel into many flat subchannels.
• MIMO: Multiple-input multiple-output — using multiple transmit/receive elements to exploit spatial diversity or multiplexing.
• Coherence time / Doppler: Time over which the channel is approximately constant; Doppler scales with relative motion and is affected by the conversion to audio speeds.
• DMA ping-pong buffers: A double-buffering technique used to stream audio samples to/from ADC/DAC with low CPU overhead for real-time processing.

With those ideas in mind you will be able to follow the architecture, the curriculum examples, and the tradeoffs Dan discusses — and evaluate how a low-cost, wavelength-consistent audio platform could fit into your lab or course.

This overview is AI-generated from the session transcript. Spot an issue? Let us know.