When would you use auditory highlighting? You can use it when you are trying to introduce a new topic to a child of any language level. If you working with prepositions you may want to highlight the preposition (the block is under the table.) You can use it when you're reading to your child to help him/her pick out the most important details. You may then want to go back and ask comprehension questions and see if the verbal emphasis helped your child to remember the information.
Practice this the next time you are working with your child! See if he/she clues into the important things you're saying. Don't forget to have fun!