Sentence:  What is interesting to note here is that the 2⁄3 gain can be seen to <WSD>overamplify</WSD> over the curved line of the impaired ear more than underamplifies, whereas the 1⁄3 gain curve illustrates the opposite, where it tends to underamplify sound to the ear. 
Meaning of the word marked with <WSD> tags:  To amplify to an extent that is undesirably loud.