The computer's on-off music is gone, the sound card is not broken, and the sound is set as the default.

I hope I can help you: First, make sure the hardware is ok. If there is nothing wrong with the speaker and sound card, if you have tested it on other machines and it is really in good condition, you can continue to watch it. Second, make sure all the connecting wires are completely correct. Then turn on the speaker power and turn on the volume switch. Third, install the driver of the sound card correctly. If it is an onboard sound card, it is best to install the driver provided on the motherboard driver disk. In fact, the computer can't make sound, and many times it is because the sound card driver is incorrect. Generally speaking, after the sound card driver is installed, there will be a small speaker icon in the taskbar in the lower right corner. If you are sure that the driver is installed correctly, let's take a look at the volume setting in the computer. The specific method is: double-click the small speaker icon in the taskbar, and check whether the volume control and waveform are turned off to the minimum or set to mute in the pop-up volume control dialog box. If these two options are not available in the dialog box, click Options menu-Select Properties-Select the volume control and waveform in Show the following volume controls, and then make the correct settings. Note: The fourth step can only be set after the sound card driver is installed correctly. Special reminder: in fact, many times, the reasons why computers can't work normally are glitches and soft faults. Careful analysis can easily solve the problem in many cases.