A common problem with the foam ear plugs is not inserting them in far enough. Twist them tightly. Put them in your ear so just a bit protrudes. As they expand, you will hear the sounds being reduced. You will still be able to hear a conversation but the volume will be less and the background noise will be very reduced. If someone can see them both as they look at you, you have not inserted them enough. They should be almost fully hidden by the small bump over your ear canal.

There are some customizable ear plugs that you warm up and insert. They cool and mold to your ear's shape. They work good too.

The bell shaped foam plugs and the ones with strings in them do not work very well.

I have used ear plugs for more than ten years. I have tried all kinds except the heat customizable ones.