Low or No Background Audio:
Understanding SC 1.4.7
[begin change][end change]1.4.7 Low or No Background Audio: For audio content that (1) is not an audio CAPTCHA and (2) contains speech in the foreground, at least one of the following is true: (Level AAA)
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 sound effects.
Note: [begin add]Per the definition of "decibel,"[end add] background sound that meets this requirement will be approximately [begin add]four times quieter than[end add][begin delete]one quarter as loud as[end delete] the foreground speech content. [2460]
Intent of this 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 [begin add]can separate the speech from background sounds or other noise[end add][begin delete]can understand the speech. Individuals who are hard of hearing have difficulty separating speech from background sounds or other noise. [2526] [end delete] Background sound that meets this requirement will be approximately [begin add]four times quieter than[end add][begin delete]one quarter as loud as[end delete] 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 1.4.7:
People who are hard of hearing often have great difficulty separating speech from background sound.
Examples of Success Criterion 1.4.7
Related Resources
Resources are for information purposes only, no endorsement implied.
Techniques and Failures for Success Criterion 1.4.7 - Low or No Background Audio
Each numbered item in this section represents a technique or combination of techniques that the WCAG Working Group deems sufficient for meeting this Success Criterion. The techniques listed only satisfy the Success Criterion if all of the WCAG 2.0 conformance requirements have been met.
Sufficient Techniques
- [begin delete]
Not including audio content (future link)
[end delete]
Additional Techniques (Advisory) for 1.4.7
Although not required for conformance, the following additional techniques should be considered in order to make content more accessible. Not all techniques can be used or would be effective in all situations.
Providing a way for users to adjust auditory levels of foreground and background sound independently (future link)
Common Failures for SC 1.4.7
The following are common mistakes that are considered failures of Success Criterion 1.4.7 by the WCAG Working Group.
(No failures currently documented)