## 1 Introduction  
As one of the fastest growing technologies in the emerging Internet of Things (IoT) environment, low power wireless sensor networks are expected to realize IoT applications and to provide connectivity for remote smart objects. The basic concept of IoT is that various smart objects can be automatically linked into a network for interacting with humans through perception and networking technologies [1]. Smart objects in the IoT have the ability to send information through the Internet to provide the interaction among multiple things and people. IoT is opening tremendous opportunities for novel applications that promise to improve the quality of people life. The development of IoT technologies can be applied to a huge variety of applications, such as intelligent power grid [2], healthcare [3], environmental monitoring [4], localization [5], etc. In an AAL context where assisted living technologies are based on ambient intelligence, smart objects need to use wireless communications because of the requirements of supporting mobile applications and remote monitoring of people. AAL can be used for detecting and preventing distress situations, improving wellness and health conditions of older adults. AAL technologies can also provide more safety for the elderly, using mobile emergency response systems, detecting domestic accidents, monitoring activities of daily living, issuing reminders, as well as helping with mobility and automation, and, overall, improving their quality of life [6; 7]. In fact, according [8], AAL should be understood as a system for extending the time people can live in their preferred environment by increasing their autonomy, self-confidence and mobility; supporting the preservation of health and functional capabilities of the elderly, promoting a better and healthier lifestyle for individuals at risk; enhancing security, preventing social isolation and supporting the preservation of the multifunctional network around the individual; supporting carers, families and care organizations; and increasing the efficiency and productivity of used resources in the ageing societies. A survey of sensors in assisted living of older people is presented in [9], such as passive infrared (PIR) and vibration sensors, accelerometers, cameras, depth sensors, and microphones. These systems should satisfy some requirements as: low-cost, high accuracy, user acceptance and privacy. These can be connected to form a network for an intelligent home designed for elderly people. The data and decision results that the sensors produce can be processed and fused over a cloud or a fog. Authors expect that the IoT will lead to remote health monitoring and emergency notification AAL systems that will operate autonomously, without requiring user intervention. In this context, audio recognition is also a promising way to ensure more safety by contributing to detection of distress situations because of the interaction of each person with her environment may be identified. In fact, in [10] detection of distress situations and monitoring of activity and health are described as two challenges to address in AAL environments. On the one hand, the identification the sounds of everyday life can be particularly useful for detecting distress situations in which the person might be. For instance, the detection of a fall can be used to call an emergency number. On the other hand, audio processing can be quite useful for the monitoring of the person's activity and the assessment of some decline. For instance, an application might consist of recognising health related symptoms such as coughing, scraping throats and sniffles. Hence, the development of WASN with low power consumption and low cost are suitable for implementing AAL systems. In this research, we are focused in the development of a low cost wireless acoustic sensor with audio processing capabilities and network connectivity to be located at the edge of a WASN. The WASN have been developed under the paradigms of both the Smart City and the IoT.