Smartphone Audio Acquisition and Synchronization Using an Acoustic Beacon With Application to Beamforming

A time-domain (TD) and a frequency-domain (FD) method for time offset (TO) compensation between received audio data are presented and implemented on Android smartphones and a processing computer. Simulations show the TD method is superior in almost all applications. Real-life experiments show the TD synchronization error is below 6 samples. A Java and MATLAB server application and an Android application are presented to acquire audio and orientation data with the intent of applying it to beamforming algorithms. Orientation data from Android smartphones is shown to be inconsistent among devices and is therefore inadequate for beamforming applications. Sampling rate offset (SRO) on Android smartphones is characterized by analyzing long duration audio recordings from the devices. Future work could include an SRO compensation algorithm, self-localization of the smartphones and distributed synchronization.