Instrumentation Synchonization Techniques for Large Microphone Arrays (original) (raw)

A Portable Matched-Field Processing System Using Passive Acoustic Time Synchronization

IEEE Journal of Oceanic Engineering, 2000

A portable matched-field processing (MFP) system for tracking marine mammals is presented, constructed by attaching a set of autonomous flash-memory acoustic recorders to a rope to form a four-element vertical array, or "insta-array." The acoustic data are initially time-synchronized by performing a matched-field global inversion using acoustic data from an opportunistic source, and then by exploiting the spatial coherence of the ocean ambient noise background to measure and correct for the relative clock drift between the autonomous recorders. The technique is illustrated by using humpback whale song collected off the eastern Australian coast to synchronize the array, which is then used to track the dive profile of the whale using MFP methods. The ability to deploy autonomous instruments into arbitrary "insta-array" geometries with conventional fishing gear may permit nonintrusive array measurements in regions currently too isolated, expensive, or environmentally hostile for standard acoustic equipment.

New hardware interface to synchronize stand-alone measurement instruments

The Measurement Instruments (MIs) connected by Hardware Interface (HI) to the node of the Distributed Measurement System (DMS) can coordinate their operations by synchronized trigger signals sent from the HIs to MIs. In the research it is taken into consideration the case that the HIs cannot be connected to DMS and, then, the MIs are standalone. With this aim a new architecture of HI is proposed for the synchronous triggering of the MI. The proposed architecture avoids the random effects of concurrency of the software processes running on PC, and reduces the random causes of delay to detect the trigger condition. From the analysis of the HI the model of the synchronization time delay is pointed out, including the opening time of the hardware components. This model permits to evaluate the effects of each cause affecting the execution of the trigger command.

FINE LANDMARK-BASED SYNCHRONIZATION OF AD-HOC MICROPHONE ARRAYS

We use audio fingerprinting to solve the synchronization problem between multiple recordings from an ad-hoc array consisting of randomly placed wireless microphones or hand-held smartphones. Synchronization is crucial when employing conventional microphone array techniques such as beam-forming and source localization. We propose a fine audio landmark fingerprinting method that detects the time difference of arrivals (TDOAs) of multiple sources in the acoustic environment. By estimating the maximum and minimum TDOAs, the proposed method can accurately calculate the unknown time offset between a pair of microphone recordings. Experimental results demonstrate that the proposed method significantly improves the synchronization accuracy of conventional audio fingerprinting methods and achieves comparable performance to the generalized cross-correlation method.

Coalignment and synchronization of the AIRS instrument suite

IEEE Transactions on Geoscience and Remote Sensing, 2003

Previous multispectral sounders have consisted of infrared and microwave instruments operated asynchronously, with the data interpolated during ground processing to common fields of view (FOVs) for geophysical retrieval processing. To help achieve the high retrieval accuracy required for the Atmospheric Infrared Sounder (AIRS) system, the four instruments making up the AIRS suite are aligned and synchronized in such a way as to achieve common FOVs without interpolation. We describe the system, how the alignment is accomplished, and the plans to verify performance after launch and compensate for misalignments that might be revealed then.

Two-way sequential time synchronization: Preliminary results from the SIRIO-1 experiment

1981

A two-way time synchronization experiment performed in the spring of 1979 and 1980 via the Italian SIRIO-1 experimental telecommunications satellite is described. The experiment was designed and implemented to precisely monitor the satellite motion and to evaluate the possibility of performing a high precision, two-way time synchronization using a single communication channel, time-shared between the participating sites. Results show that the precision of the time synchronization is between 1 and 5 ns, while the evaluation and correction of the satellite motion effect was performed with an accuracy of a few nanoseconds or better over a time interval from 1 up to 20 seconds.

Time Synchronization for High Latency Acoustic Networks

2006

Distributed time synchronization is an important part of a sensor network where sensing and actuation must be coordinated across multiple nodes. Several time synchronization protocol that maximize accuracy and energy conservation have been developed, including FTSP, TPSN, and RBS. All of these assume nearly instantaneous wireless communication between sensor nodes; each of them work well in today's RF-based sensor networks. We are just beginning to explore underwater sensor networks where communication is primarily via acoustic telemetry. With acoustic communication, where the propagation speed is nearly five orders of magnitude slower than RF, assumptions about rapid communication are incorrect and new approaches to time synchronization are required. We present Time Synchronization for High Latency (TSHL), designed assuming such high latency propagation. We show through analysis and simulation that it achieves precise time synchronization with minimal energy cost. Although at very short distances existing protocols are adequate, TSHL shows twice the accuracy at 500m, demonstrating the need to model both clock skew and propagation latency.

Time Delay Estimation Using Signal Envelopes for Synchronisation of Recordings

In this work, a method of time delay estimation for dual-channel acoustic signals (speech, music, etc.) recorded under reverberant conditions is investigated. Standard methods based on cross-correlation of the signals show poor results in cases involving strong reverberation, large distances between microphones and asynchronous recordings. Under similar conditions, a method based on cross-correlation of temporal envelopes of the signals delivers a delay estimation of acceptable quality. This method and its properties are described and investigated in detail, including its limits of applicability. The method's optimal parameter estimation and a comparison with other known methods of time delay estimation are also provided.

A WIRELESS TIME-SYNCHRONIZED COTS SENSOR PLATFORM: APPLICATIONS TO BEAMFORMING1

2002

In recent years, sensor network system has been proposed for various applications. In the past, most reported systems involve custom-made hardware. In this paper, we consider the use of Compaq iPAQ 3760s with their build-in Stron-gARM processors, ROM and RAM memories, and microphones and codecs for acoustic acquisition and processing, plus external wireless Ethernet cards for radio communication to form a distributed sensor network to perform acoustical beamforming. Time synchronization among the microphones is achieved by the Reference-Broadcast Synchronization method of Elson-Estrin. Two beamforming algorithms, based on the time difference of arrivals (TDOAs) among the microphones and least-squares estimation of the TDOAs method, and the maximum-likelihood (ML) parameter estimation method, are used to perform source detection, enhancement, localization, delay-steered beamforming, and direction-of-arrival estimation. Theoretical Cramér-Rao bound analysis of the system performance and experimental beamforming results using the iPAQs and the wireless network are reported.

Implementation and Applications of Open Sound Control Timestamps

Proceedings of the ICMC, 2008

The background, purpose, and function of Open Sound Control (OSC) timestamps is reviewed. An analysis shows that jitter-induced noise with dispersion over the millisecond range significantly degrades real-time highresolution sensor signal streams. The design of a distributed clock synchronization and event scheduling domain over an asynchronous network is described. A realization of this model is presented, created using the new micro-OSC (µOSC) hardware platform and host software components in MaxMSP. An OSC address schema for client-server clock synchronization is documented. Two new objects for MaxMSP are introduced: OSC-timetag and OSC-schedule.