The "ding" sound you hear when a microwave finishes cooking is typically produced by a small electronic component called a "buzzer" or "beeper." The purpose of the buzzer is to provide an audible signal to let you know that the cooking time has elapsed.
Inside a microwave, there is a control circuit that manages the various functions, including the timer. When the timer reaches zero, it sends a signal to the buzzer, which then generates the sound. The buzzer is usually a small electromechanical device that consists of a diaphragm or speaker and a magnetic coil. When the electrical signal is sent to the buzzer, it causes the diaphragm to vibrate, producing the audible sound you hear as a "ding."
The specific sound produced by the buzzer can vary between different microwave models and manufacturers. Some microwaves may have a softer or more melodic sound, while others may have a louder and more pronounced "ding." Additionally, some microwaves may offer options to adjust the sound level or even mute it if desired.
It's important to note that not all microwaves use an audible "ding" sound to indicate the end of cooking. Some models may have different ways of signaling the completion, such as displaying a message on the control panel, flashing lights, or simply shutting off the cooking function without any specific sound. The exact method of indicating the end of cooking can vary depending on the microwave's design and features.