It is supposed to be sufficiently small that the difference between the volume of the foreground sound (main utterance) and the volume of the background sound only has to be 20 decibels, but since it is a difficult area for web content personnel to take care, accessibility If you know that it includes video content at the time you make the policy, you should share it with the video staff in advance.
If possible, it is good to set a policy of not using the background sound in the first place if you want to explain something with a video.
|Principle||Perceivable||Information and user interface components must be presentable to users in ways they can perceive.|
|Guideline||Distinguishable||Make it easier for users to see and hear content including separating foreground from background.|
|Criterion||Low or No Background Audio
|Content that contains only recorded sounds, (1) mainly includes utterances in the foreground, (2) not speech CAPTCHA or voice logo, and (3) mainly music expressions such as songs and laps There is consideration for things that are not intended utterances.|