What's an Audiogram?
The Audiogram plots frequency or pitch from Left to Right and the loudness of sounds from Top to Bottom. Hearing test results are plotted so that the higher the marks are, the better the hearing is; and the lower the marks are the worse the hearing is.

The vowels are concentrated in the lower pitches. They carry the power of speech. The consonants are more concentrated in the higher pitches. They carry the information of speech. With high frequency hearing loss, the consonants are either not heard or are heard too faintly. This is why people say, "I hear you, but I can't understand what you are saying." Also, this is why people with hearing loss accuse other people of mumbling.