Thermal insulation is one of the important performance indicators of insulated cups. How to determine the insulation of a cup? Some netizens claim that blowing a breath into the inner lining of a thermos cup and then holding it to their ear, if there is a noticeable "buzzing" sound, it indicates that the cup has good insulation properties. This method is figuratively referred to as the "blowing air and listening to sound" method on the internet. Is this method reliable? The so-called 'blowing air to hear sound' is actually similar to the principle of 'shell resonance' Associate Professor Gong Youpin from the School of Physics at Chongqing University told reporters that when people place semi open objects such as cups towards their ears, the airflow outside the cup will enter the inside of the cup, and then repeatedly return to the inner wall of the cup and ear canal, forming a "buzzing" sound. He further explained that we can hear a "buzzing" sound when blowing air into any material cup, even without blowing air, because the "buzzing" sound is actually the noise generated by air flow. So, what kind of insulated cup has better insulation performance? Unlike conventional cups, insulated cups have a vacuum layer and a small mouth that can block heat conduction and convection. The outer wall of the inner liner is often coated with a layer of silver or copper, which helps reduce heat radiation. Gong Youpin told reporters that the vacuum layer technology of insulated cups is the key to determining the insulation effect, but for ordinary consumers, it is difficult to judge the quality of the process. Therefore, he suggests that consumers purchase products with compliance labels and certificates when choosing insulated cups. In addition, it is also possible to select insulated cups by comparing the insulation test reports of different products. In the face of the highly segmented insulated cup market, experts remind that in addition to paying attention to the insulation effect, it is also extremely important to choose the appropriate material for the insulated cup according to one's own needs. The reporter searched multiple e-commerce platforms using the keyword "thermos cup" and found that the inner lining and filter screen materials of thermos cups on the market are mostly 304 stainless steel, 316 stainless steel, etc., while the lid materials are mostly silicone, polypropylene (PP), etc. Gong Youpin suggests that although food grade 304 stainless steel insulated cups are the most common, if there is a long-term need to brew tea or hold acidic drinks, it is best to choose medical grade 316 stainless steel insulated cups with stronger corrosion resistance. The cup lids made of silicone and PP materials are relatively safe and do not easily release harmful substances at high temperatures, so you can rest assured when purchasing. Gong Youpin reminds that with the upgrading of people's consumption needs, the styles of thermos cups are updated and the functions have become more comprehensive, such as temperature display, water reminder and other intelligent functions. Consumers should prioritize selecting insulated cup products with complete labeling, advanced technology, and safe materials based on their own usage needs when making purchases. (New Society)