THE SHORT ANSWER
Here's the approach.
Voice Isolation gives detectable human speech priority over other sound. Enable it manually in the Audio inspector; automatic audio analysis does not turn it on for you.
Audio enhancements operate on components. For a clip with multiple components, choose the intended component first. Apple warns that isolating several components that play together can produce garbled sound; turn the feature off on one or more components if that happens.
Related tutorial.
Full tutorialThis is a supplemental tutorial. Its compatibility with Final Cut Pro 10.8 has not been confirmed. Use the written steps and version-specific sources for the controls.
By Ripple Training. YouTube oEmbed confirmed the title, creator and thumbnail. The software version shown in this video has not been verified. No watched-content review, answer timestamps, transcript, duration or upload date is asserted. Playback was not tested.
Step by step.
Final Cut Pro 10.8- 01
Choose the audio
Select the timeline clip. For a clip with multiple audio components, select the component that contains the dialogue.
- 02
Enable Voice Isolation
Open the inspector, click Audio, and select Voice Isolation in Audio Enhancements.
- 03
Adjust and compare
Move the Amount slider while listening to the dialogue and surrounding sound. Toggle the checkbox to compare the processed and original sound.
Sources & version notes
Written for Final Cut Pro 10.8. Menu names and available features can differ in other versions.
Version reference: Final Cut Pro 10.8Written answer checked against the linked official documentation for Final Cut Pro 10.8. Related videos have metadata verification only; they are supplemental resources, with no verified answer-specific timestamps or software-version compatibility assertion.