An audiometer is used to check your hearing. It measures your level of hearing by using 20 decibels, units used to measure the intensity of a sound or the power level of an electrical signal, at 500, 1,000, 2,000, 3,000 or 4,000 hertz, which is the SI unit of frequency. You put on a set of headphones and the doctor or nurse will change the tones.All you have to do is tell them if you can hear the tone. They will do one ear at a time. Don't worry about the volume of the machine. I promise that it will not bust your eardrums! If for any reason you cannot hear the tone, they will know you have a hearing issue, and they will either do something themselves or send you to a more experienced ear doctor, an otologist.