Smart Sound Control in Acoustic Sensor Networks: a Perceptual Perspective

Abstract

Audio systems have been extensively developed in recent years thanks to the increase of devices with high-performance processors capable of performing more efficient audio processing. In addition, the expansion of wireless communications has given the possibility of implementing networks in which devices can be placed in different locations without physical limitations, unlike wired networks. The combination of these technologies has led to the emergence of Acoustic Sensor Networks (ASN). An ASN is composed of nodes equipped with audio transducers, such as microphones or speakers. In the case of acoustic field monitoring, only acoustic sensors (or microphones) need to be incorporated into the ASN nodes. However, in the case of control applications, the nodes must interact with the acoustic field through loudspeakers.The ASN can be implemented through low-cost devices, such as Raspberry Pi or commercial mobile devices, capable of managing multiple microphones and loudspeakers and offering good computational capacity. In addition, these devices can communicate through wireless connections, such as Wi-Fi or Bluetooth. This ASN design provides high processing power and flexibility due to the processors and the wireless communications offered by the current mobile devices. Therefore, in this dissertation, an ASN composed of commercial mobile devices connected to wireless speakers through a Bluetooth link is proposed. Additionally, the problem of synchronization between the devices in an ASN is one of the main challenges to be addressed since the audio processing performance is very sensitive to the lack of synchronism. Therefore, a deep analysis of the synchronization problem between commercial devices connected to wireless speakers in an ASN is also carried out. In this regard, one of the main contributions is the analysis of the audio latency of mobile devices when the acoustic nodes in the ASN are comprised of mobile devices communicating with the corresponding loudspeakers through Bluetooth links. A second significant contribution of this dissertation is the implementation of a method to synchronize the different devices of an ASN, together with a study of its limitations. Finally, the proposed method has been introduced in order to implement personal sound zones (PSZ) applications. Therefore, the implementation and analysis of the performance of different audio applications