Success Criterion 1.4.7: Low or No Background Audio

Understanding Success Criterion: 

For prerecorded audio-only content that (1) contains primarily speech in the foreground, (2) is not an audio CAPTCHA or audio logo, and (3) is not vocalization intended to be primarily musical expression such as singing or rapping, at least one of the following is true:

  • No Background: The audio does not contain background sounds.
  • Turn Off: The background sounds can be turned off.
  • 20 dB: The background sounds are at least 20 decibels lower than the foreground speech content, with the exception of occasional sounds that last for only one or two seconds.

Note: Per the definition of "decibel," background sound that meets this requirement will be approximately four times quieter than the foreground speech content.

Accessibility Level: 
AAA
Intent of Success Criterion: 

The intent of this Success Criterion is to ensure that any non-speech sounds are low enough that a user who is hard of hearing can separate the speech from background sounds or other noise foreground speech content.
The value of 20 dB was chosen based on Large area assistive listening systems (ALS): Review and recommendations [LAALS] and In-the-ear measurements of interference in hearing aids from digital wireless telephones [HEARING-AID-INT]

Specific Benefits of Success Criterion: 
  • People who are hard of hearing often have great difficulty separating speech from background sound.