Engineers at Imperial College London have demonstrated a new method for capturing a far wider range of sound without increasing digital resolution, challenging a nearly 90-year-old convention in digitisation. This breakthrough, known as Unlimited Sensing, opens new possibilities for applications in healthcare, environmental sensing, and artificial intelligence.
For decades, engineers have managed the trade-off between capturing quiet and loud sounds by balancing loudness against the number of bits used. The new approach, demonstrated by researchers at Imperial College London, deliberately folds loud signals into a smaller range before digitisation. Although the resulting waveform may appear scrambled, its mathematical structure allows the original sound to be reconstructed.
In experiments using just six bits per sample, the prototype achieved at least 18 dB greater dynamic range than a conventional six-bit converter. Listening studies involving 52 participants also indicated that reconstructed audio received higher quality ratings than conventional recordings at the same bit depth.
This advancement builds on nearly 90 years of digitisation research, including the work of Imperial alumnus Dr Alec Reeves and Claude Shannon. The team's solution, developed by researchers Dr Ruiming Guo, Yuliang Zhu, and Dr Ayush Bhandari, uses a mathematical principle similar to a clock wrapping around to represent large signal amplitudes within a smaller range, allowing the original signal to be recovered.
Dr Ruiming Guo, lead author and Research Associate in Imperial's Department of Electrical and Electronic Engineering, stated, “Reeves and Shannon established the ideas that made digital communication possible. Those ideas are not wrong. What has changed is that modern computation allows us to ask whether the analogue signal must still be presented to the converter in the same way.”
The technology's potential extends beyond audio, impacting digital stethoscopes, environmental sensors, and AI systems. Dr Ayush Bhandari, Associate Professor in Imperial's Department of Electrical and Electronic Engineering, commented, “Great music lives in its contrasts — from the faintest whisper to the loudest crescendo. Yet conventional digital recording forces compromises between capturing these extremes. We asked a radically different question: what if we changed what the bits represent, rather than simply adding more of them?”
The study, titled ‘Re-thinking Digital Audio via Unlimited Sensing: Theory, Algorithms, and Hardware Validation’, was published in IEEE Transactions on Audio, Speech and Language Processing and supported by the European Research Council.
