A.7 WCAG 2.1 Success Criterion 1.4.7 − Low or No Background Audio
Ideally, do not place background sounds in audio clips. If this cannot be avoided, provide a clearly labelled function to enable the user to turn the audio off and ensure the foreground sound is approximately four times as loud as the background sound.
Before Rectification
The background audio has a high chance of overpowering the actual dialogue. This becomes an issue for persons with hearing impairments.
After Rectification
An effort should be made to reduce the background sound as much as possible. At the bare minimum, make sure that if a background sound does exist, it is four times as quiet as the foreground sound/dialogue.
WCAG 2.1 Reference:
https://www.w3.org/WAI/WCAG21/Understanding/low-or-no-background-audio