-★ 1. "Car horn" is similar to a buzzer. There is a contact in the middle that makes it on and off with the movement of the diaphragm. When the battery is connected with direct current, the diaphragm is sucked in, the contact is disconnected, the diaphragm is reset, the contact is closed again, and then it is repeatedly sucked in and reset, so it will automatically sound.

—★ 2. The diaphragm (paper basin) of the "loudspeaker for acoustics" is connected with the voice coil. When an AC audio signal is applied in the magnetic field of the magnet, the voice coil (interacting with the magnetic field of the magnet) drives the diaphragm and emits an audio signal. If you connect DC (like a car horn), the diaphragm will not vibrate and will not make sound.

-★ 3. "Can a horn whistle be used as a music horn?" ..... The two have different sound principles and cannot replace each other.