Metal Detector Headphones
Perhaps the most important reason to wear headphones is the clarity that they provide. They'll allow you to pick up signals that may be impossible to hear with just the external speaker on the detector. Also, headphones will help you identify different metals. If you're hard of hearing it will allow you to hear the low tone targets that otherwise might be missed.
What other factors should you consider when buying headphones and why?
Brands - buy the headphones that are specific to your metal detector.
Look for a brand that provides a good fit so that ambient noise will be kept to a minimum. Ask questions before you make a purchase so that your dealer can help make the right choice. You spend a lot of your time searching and walking with your metal detector and you want to have all the right tools in order to get the most from the hobby.