CASSS ¢ Coherent Acoustic Source Synchronization System

The Interdisciplinary Consulting Corporation (IC2) proposes to develop a low-power, embeddable electronic module that provides coherence between an array of consumer devices, allowing the devices to be used in reception and transmission beamforming applications. In a previous Phase II SBIR (NASA contract #80NSSC20C0090), IC2 developed a æTime Synchronization ModuleÆ (TSM) as a subsection of a distributed, wireless, instrumentation-grade acoustic acquisition system (WArray). This systemÆs main application is beamforming for acoustic source localization in ground-test flyover arrays of commercial aircraft. The goal of this proposal is to adapt the proven TSM technology to provide coherence in commercial-off-the-shelf (COTS) devices commonly found in consumer and commercial spaces. IC2 has chosen to demonstrate the TSM technologyÆs ability to achieve coherence in consumer devices by embedding it in æsmart speakersÆ. Smart speakers are defined here as any device that contains a microphone and speaker, and can transmit and receive audio signals over the internet from a remote system such as desktop Voice over Internet Protocol (VOIP) phones, web meeting systems, and wireless smart assistant devices. The method for modifying the smart speakers with the TSM proposed will not affect the commercial deviceÆs functionality or appearance, allowing the æend-userÆ to continue using the device for its original purpose without knowledge of the modification while also allowing a æbeamforming-userÆ to leverage an array of modified smart speakers for beamforming applications. The TSM technology is not limited to acoustic applications, but it has been chosen as the demonstration vehicle because of IC2Æs expertise with acoustic acquisition and beamforming. To achieve beamforming synchronization for the WArray system, IC2 developed a specialized GPSDO (TSM) that generates a standard 10 MHz signal, a PPS signal, and a customizable trigger signal that is aware of, and programmable with respect to, absolute time. The TSM allows multiple wireless acquisition units to wirelessly synchronize their analog-to-digital converter (ADC) clocks and trigger an acquisition simultaneously. Although the current TSM functions by locking to the PPS signal of a GPS module, it is planned to adapt this system to function on timing signals available from other technologies such as Ultra-Wideband (UWB) radio technology, enabling it to function in indoor applications and other GPS-denied environments. The TSM modules currently exist, are functional, and have been successfully deployed in testing scenarios including a flyover test deployment at NASA LangleyÆs UAS test range in October 2022.Ā Because the system is modular and the synchronization is customizable, the TSM can be integrated into commodity hardware with minor modifications to provide coherence between a broad range of devices and applications.