Energy Efficiency is Not Enough:Towards a Batteryless Internet of Sounds

Abstract

This position paper advocates for digital sobriety in the design and usage of wireless acoustic sensors. As of today, these devices all rely on batteries, which are either recharged by a human operator or via solar panels. Yet, batteries contain chemical pollutants and have a shorter lifespan than electronic components: as such, they hinder the autonomy and sustainability of the Internet of Sounds at large. Against this problem, our radical answer is to avoid the use of batteries altogether; and instead, to harvest ambient energy in real time and store it in a supercapacitor allowing a few minutes of operation. We show the inherent limitations of battery-dependent technologies for acoustic sensing. Then, we describe how a lowcost Micro-Controller Unit (MCU) could serve for audio acquisition and feature extraction on the edge. In particular, we stress the advantage of storing intermediate computations in ferroelectric random-access memory (FeRAM), which is nonvolatile, fast, endurant and consumes little. As a proof of concept, we present a simple-minded detector of sine tones in background noise, which relies on a fixed-point implementation of the fast Fourier transform (FFT). We outline future directions towards bioacoustic event detection and urban acoustic monitoring without batteries nor wires. CCS CONCEPTS• Hardware → Sound-based input / output; Digital signal processing; Power estimation and optimization; Impact on the environment; • Computer systems organization → Real-time systems; • Networks → Sensor networks.

The Internet of Sounds: Convergent Trends, Insights, and Future Directions

“…Among the most drastic are the autonomy of the sensors, autonomy meaning here low dependence to energy harvesting and maintenance [152].…”

“…2) Audio Things: Various IoT devices designed to provide or collect sonic information to/from users have been proposed while others are currently under study [152]. An illustrative example is represented by sonic shoes devised for clinical or sport training applications [9], [158].…”

“…Resorting to embedded power storage reduces the ease of maintenance and increases the dependency on polluting materials. Those issues call for innovative solutions such as batteryless designs [281]. While this kind of hardware potentially allows simpler and more reliable networks designs, it also opens an interesting challenges in sparse network managment to be able to produce reliable estimates of quantities of interest from sources of information that are only intermittently able to record, process and transmit.…”

In‐Sensor Passive Speech Classification with Phononic Metamaterials

“…For such tasks, phononic computing is an excellent candidate. While phononic signal processing is significantly slower than electric circuits, a large class of highly relevant signals (e.g., speech commands, [20] bioacoustic signals, [21] gas concentrations, [22] or intraocular pressure [23] ) naturally occur at lower frequencies, and for these in-sensor batterypowered applications, high energetic efficiency is of utmost importance.…”

BirdVox: Machine listening for bird migration monitoring

“…However, the design of a CPS necessarily incurs practical risks in terms of reliability, and the case of bioacoustic sensor networks is no exception. Indeed, the ARUs, which constitute the physical frontend of the system, are typically made from low-cost parts [29], deployed in extreme weather conditions [30], and under strong constraints of energy supply [31]. On the “cyber” side of the CPS, machine listening remains a fallible technology, with multiple forms of technical bias.…”