Sound will come out of speakers even when headphones are plugged

When i play sound (like YouTube or Spotify) on my computer it will come out the speakers even when my headphones are plugged it.I have a Acer so if anyone knows a way to fix this please so.Also i tried to look it up but i couldn't find where the people said to go (The hardware) well i found it but the headphones wouldn't come through.

Please help