Voice enhancement is the process of improving intelligibilty of speech. It starts by analyzing the recording to determine what conditions exist and what processes will be needed.
It often begins with Background Noise Reduction as its first process. Our next step is to focus on the frequencies of our target voice. If the voice sounds "muddy" or bassy, we might add some high frequency equalization to improve clarity. Conversely, if the voice recording is "shrill" or "tinny" we might add midrange or low frequency equalization.
Intelligibility is also very dependent on having the frequencies present where consonants are created. For example, we need to make sure 1500 hz is adequately present to ensure that P, H , G and the sounds CH and SH are heard clearly.