WCAG 1.4.7 Low or No Background Audio: Keep Speech Clear and Audible

What This Criterion Requires

WCAG 1.4.7 requires that for prerecorded audio-only content that contains primarily speech in the foreground, background sounds are either absent, can be turned off, or are at least 20 decibels lower than the foreground speech content (with the exception of occasional sounds lasting no more than one or two seconds). This 20-decibel difference means the background is roughly four times quieter than the speech. The criterion addresses a fundamental challenge for people who are hard of hearing: distinguishing speech from competing background sounds. While a person with typical hearing can often mentally filter out background music or ambient noise, people with hearing loss experience a reduced ability to separate audio streams, a phenomenon known as decreased auditory scene analysis. Even mild hearing loss, which affects an estimated 1.5 billion people globally, can make speech incomprehensible when background audio competes with it. This criterion applies to podcasts, audio articles, narrated tutorials, voice instructions, audio descriptions, and any other audio content where speech is the primary content. It does not apply to music, sound effects that are the primary content, or audio that is incidental. Meeting this criterion benefits not only people with hearing disabilities but also anyone listening in noisy environments, people whose first language differs from the audio content, and older adults experiencing age-related hearing changes.

Why It Matters

Hearing loss is one of the most prevalent disabilities worldwide, affecting approximately 1.5 billion people according to the World Health Organization, with 430 million experiencing disabling hearing loss. Age-related hearing loss (presbycusis) affects roughly one-third of people over 65 and half of those over 75. One of the earliest and most significant effects of sensorineural hearing loss is reduced ability to understand speech in noise. Research published in the Journal of the Acoustical Society of America consistently demonstrates that people with hearing loss require a significantly better signal-to-noise ratio than those with typical hearing to achieve the same level of speech comprehension. A person with typical hearing might understand speech at a 0 dB signal-to-noise ratio (equal loudness), while a person with mild hearing loss may need a +10 to +15 dB advantage. Background music in podcasts, ambient sound effects in tutorials, and music beds under narration can transform comprehensible content into an unintelligible blur for these listeners. Hearing aids and cochlear implants help but do not restore normal auditory processing, particularly in the presence of competing sounds. Beyond hearing disability, the global rise in audio content consumption through podcasts (over 500 million listeners worldwide) and audio articles makes this criterion increasingly important. People commonly listen in noisy environments such as commuting, exercising, or working, where even typical hearing is challenged by poor signal-to-noise ratios.

Common Failures and How to Fix Them

<audio controls>
  <source src="podcast-ep12.mp3" type="audio/mpeg">
  <!-- Audio file has music bed at -10dB under speech -->
</audio>
<!-- No option to listen without background music -->

<audio controls>
  <source src="podcast-ep12-clean.mp3" type="audio/mpeg">
  <!-- Audio file has no background music, or music
       is at least 20dB below speech level -->
</audio>
<p><a href="podcast-ep12-transcript.html">Read the
  full transcript</a></p>

<video controls>
  <source src="tutorial.mp4" type="video/mp4">
  <!-- Narrator speaks over office ambiance at -8dB -->
</video>

<video controls>
  <source src="tutorial.mp4" type="video/mp4">
  <track kind="captions" src="tutorial-en.vtt"
    srclang="en" label="English" default>
</video>
<!-- Audio mix: ambiance at -25dB below narrator -->
<p>Tip: Enable captions for the best experience.</p>

<div id="welcome-audio">
  <audio autoplay>
    <source src="welcome-with-music.mp3">
  </audio>
  <button onclick="toggleMute()">Mute</button>
</div>

<div id="welcome-audio" role="region"
  aria-label="Welcome message">
  <audio id="narration" src="welcome-voice-only.mp3"
    controls></audio>
  <label for="bg-volume">Background music volume:</label>
  <input type="range" id="bg-volume" min="0" max="100"
    value="0" aria-label="Background music volume">
  <audio id="bg-music" src="welcome-bg.mp3" loop></audio>
</div>

How to Test

1. Listen to prerecorded audio content that contains speech. Subjectively assess whether background sounds make the speech difficult to understand.
2. Use audio editing software such as Audacity to measure the difference in decibel levels between foreground speech and background audio. The background should be at least 20 dB below the speech.
3. Check whether the content provides a mechanism to turn off background sounds independently of foreground speech.
4. Verify that any background sounds lasting more than one or two seconds maintain the required 20 dB separation from foreground speech throughout the recording.

CMS-Specific Guidance

This criterion commonly causes issues on these platforms:

• Wordpress Accessibility Checklist
• Squarespace Accessibility Checklist
• Wix Accessibility Checklist

Further Reading

• Video Accessibility Captions Guide
• Accessible Content Writing Guide
• Wcag Explained Plain English

Related WCAG Criteria

• WCAG 1.4.2
• WCAG 1.2.1
• WCAG 1.2.2