Your sound does not come form the monitor but from the computer. The computer will have sound out ports.
You put the post in the title which cuts it off, try again with details about what you are trying to connect and for what purpose.
If you are trying to use your computer monitor attached to the cable box, you need to get an HDMI to VGA active converter, that will split the signal to VGA and audio. The Audio part will go into the input of your speakers, the VGA will go to the monitor.
An active converter will cost close to what a monitor with HDMI and speakers would cost, especially if you buy a used one. Spend $40 on a converter or a bit over $100 for a new monitor, or that 40 or 50 on a used one.