ABSTRACT
An acoustic emitter based on electrical-mechanical transduction is designed to have a projected emission pattern. However, due to constructive features, design flaws, and different material qualities, the final device does not match project specifications which may cause, among other things, the reduction of performance, loss of emission power, and undesirable noise. In this work, an apparatus for acoustic characterization comprising a turntable and an arc is developed to estimate the emission power of acoustic emitters. The time-stretched pulse method is used as a test signal to obtain the emission power for each emitter's azimuth and elevation angles. Processing the acquired signals gives an estimated radiation pattern in the three-dimensional space, which visually allows the analysis of the emission characteristics of the acoustic source.
ABSTRACT
In many countries, water quality monitoring is limited due to the high cost of logistics and professional equipment such as multiparametric probes. However, low-cost sensors integrated with the Internet of Things can enable real-time environmental monitoring networks, providing valuable water quality information to the public. To facilitate the widespread adoption of these sensors, it is crucial to identify which sensors can accurately measure key water quality parameters, their manufacturers, and their reliability in different environments. Although there is an increasing body of work utilizing low-cost water quality sensors, many questions remain unanswered. To address this issue, a systematic literature review was conducted to determine which low-cost sensors are being used for remote water quality monitoring. The results show that there are three primary vendors for the sensors used in the selected papers. Most sensors range in price from US$6.9 to US$169.00 but can cost up to US$500.00. While many papers suggest that low-cost sensors are suitable for water quality monitoring, few compare low-cost sensors to reference devices. Therefore, further research is necessary to determine the reliability and accuracy of low-cost sensors compared to professional devices.
