An
audiogram is a graph that shows the audible threshold for standardized frequencies as measured by an
audiometer. The Y axis represents intensity measured in decibels and the X axis represents frequency measured in Hertz. The threshold of hearing is plotted relative to a standardised curve that represents 'normal' hearing, in dB(HL). They are not the same as
equal-loudness contours, which are a set of curves representing equal loudness at different levels, as well as at the
threshold of hearing, in absolute terms measured in
dB SPL (sound pressure level).