Ping-pong balls can absorb the city's din
Simple and inexpensive things like pinpong balls, which instantly bring to mind their use in the fastest sport played on foot called table tennis, can absorb the unbearable din caused in a city, especially Indian cities where rules concerning decibel levels are thrown to the wind. Low-frequency sounds can trigger earaches, respiratory impairment, irritability, and other long-term adverse effects. Because it is produced by a range of sources and is less affected by structures than higher-frequency sound, low-frequency noise can be challenging to avoid.
But now, researchers from the University of Lille in France and the National Technical University of Athens in Greece have found that this very low-frequency noise, which is known to be bad for health, can be mitigated using simple ping pong balls, albeit with some modifications. The researchers used ping pong balls to create a low-frequency insulating panel structure to present an economical alternative to acoustic insulators for both low-cost and potential recycling. Acoustic metasurfaces are materials specially engineered to manipulate sound waves.
This metasurface uses hollow ping pong balls with small holes punctured in each, modelling Helmholtz resonators, which have the ability to capture ambient sound waves at their natural frequency, and which when coupled, lead to the occurrence of two resonance frequencies. More resonant frequencies mean that the device is able to absorb more sound. The researchers kept adding more holed ping pong balls, until their device resembled a square sheet of punctured ping pong balls, multiplying the number of resonant frequencies absorbed, thus achieving noise absorption. By adjusting the number of balls, the holes made in them, and the size of the holes, the researchers could change the metasurface’s acoustic properties, creating a sound absorption panel without expensive materials. The researchers are now looking at presenting an economical alternative to acoustic insulators at very low costs.
Biodegradable sensors to aid precision agriculture
Limited land and water have created a need for precision agriculture, which involves the use of remote sensing technology to monitor air and soil environmental data in real-time to help optimize crop output. The main aim is to maximize the sustainability of such a technology, which becomes critical to achieving optimal quality of production at minimal costs and reducing costs. This requires sensor networks to gather environmental information for the proper allocation of resources — basically, assess when and where resources are needed and in what quantities. While drones and satellites are already being used, these cannot precisely capture data on humidity and soil moisture levels.
The need has been for moisture-sensing devices on the ground — in fact, in the soil itself. But there is a problem: these need to be gathered at the end of their utility if they are not biodegradable. Now scientists from Osaka University in Japan have developed soil moisture-sensing sensors that can be powered as well as can transmit data in a wireless mode, and — most importantly — are biodegradable, allowing deployment in high numbers in the soil itself.
The system comprises several sensors, a wireless power supply, and a thermal camera for acquiring and transmitting sensing and location data in the wireless mode. The sensors are eco-friendly, composed of a nano paper substrate, a natural wax protective coating, a carbon heater, and tin conductive lines. Its wireless power transmission to the sensor corresponds to the temperature of the sensor’s heater and the moisture content of the surrounding soil. A thermal camera captures images of the area to simultaneously collect soil moisture-content data and sensor location data. At the end of the crop season, the sensors can then be tilled into the soil for biodegradation.