Why does the sound of wireless earphones tend to be interrupted on the platform of the station?

If you are listening to music on a train while using wireless earphones, the sound may be interrupted when you arrive at the station platform. Some earphones have severe sound interruptions, while others rarely occur, and the symptoms differ depending on the product. yeah. The reason is the congestion of the wireless communication (Bluetooth) band used by wireless earphones and the communication procedure of Bluetooth. Since the reception sensitivity of wireless earphones and the output of the transmitting device such as a smartphone can be covered to some extent, the sound may not be interrupted, but it tends to occur in places such as station platforms where communication conditions are severe.

Why does the sound of wireless earphones tend to be interrupted on the station platform? Bluetooth, which most wireless earphones use, has a function called "Frequency Hopping (FHSS)" that provides 79 channels in 1MHz increments in the 2.4GHz band (2400-2483MHz) and communicates while switching at a speed of 1600 times per second. hold. In addition, there is also a function called "adaptive frequency hopping (AFH)" that stabilizes communication by avoiding frequencies that are in use by other wireless devices, suppressing radio interference. However, when a crowded train arrives at a station platform (which is also crowded), the 2.4GHz band becomes "congested", and there may be moments when even FHSS/AFH cannot find a switch destination. This is the cause of sound interruptions, and it tends to occur not only in crowded trains and station platforms, but also in places where many users of devices that use the 2.4 GHz band, such as wireless earphones and smartphones, come and go.