IPX4 is an ingress protection rating, which is an internationally recognized standard that specifies the resistance of electronic devices against the ingress of foreign objects and liquids. The code consists of two digits. The first digit, replaced by the letter "X" in this case, indicates protection against solid particles, such as dust. The letter "X" means that the device has not been tested for this resistance. The second digit, here "4", describes the level of protection against water. Specifically, the digit 4 guarantees that headphones, a speaker, or a player are protected against splashing water from all directions. In practice, this means that the device can easily withstand rain or sweat during sports. However, it is not waterproof and therefore not suitable for submersion in water, for example, when swimming or showering.