If your monitor doesn't have speakers, only way of getting sound is either usb headphones (from ps4) or an idea is to get a sound bar with headphone jack with optical in. HDMI for video and optical for audio.
Analog mic in to PC might work but would be messing around with digital to analog audio conversions. PS4 usb to 3.5mm powered converter, kind of like using usb headphones but with 3.5mm jack end and have the pc route sound that way. Sound quality would be lacking id imagine though.
Headphones/sound bar would be best way imo
Lakken :
A PC monitor only gets visual through hdmi from GPU and sound from the soundcard.. It least my old pc monitor with speakers.
Gpus also carry sound via hdmi and monitors with speakers will work just need to enable the gpu audio in audio playback devices.