Checkpoint 05: Sound

Audio content in PDFs must be accompanied by equivalent alternatives. Users who are deaf, hard of hearing, or in sound-restricted environments must be able to access the same information presented in audio form.

What This Means

Sound in PDFs can appear in several forms:

• Media annotations: Video or audio clips embedded within the document
• Audio annotations: Sound clips attached to specific document elements
• JavaScript beeps: Alert sounds triggered by scripts

PDF/UA requires that any information conveyed through sound must also be available in another form. This could be:

• Text transcripts for spoken content
• Captions or subtitles for video with audio
• Visual alerts alongside audio notifications
• Text descriptions of significant sounds

The key principle is that no information should be available only through audio. A user who cannot hear the audio must be able to access equivalent content through visual or text-based means.

Why It Matters

Audio-only content creates barriers for significant user populations:

• Deaf users: Approximately 5% of the world's population has disabling hearing loss
• Hard of hearing users: Many more experience partial hearing loss, especially among older adults
• Non-native speakers: Text alternatives help users who struggle with spoken language
• Noisy environments: Users in public spaces or workplaces may not be able to hear audio
• Silent environments: Libraries, hospitals, and shared spaces often require silent operation
• Assistive technology users: Screen readers cannot interpret audio content meaningfully

Beyond accessibility, audio alternatives improve content usability for everyone. Transcripts are searchable, can be translated, and allow users to consume content at their own pace.

Common Violations

The Matterhorn Protocol defines three failure conditions for sound content. All three require human testing because automated tools cannot analyze audio content or determine whether adequate alternatives exist.

05-001: Media Annotation Present Without Alternative (Human Testing)

What's Wrong: The PDF contains a media annotation (typically video or audio) with audio content, but no text alternative is provided for the audio information. Users who cannot hear the audio have no way to access that content.

How to Identify:

• Open the PDF and look for embedded media players
• Play any video or audio content
• Check whether there are captions, subtitles, or transcripts
• Look for text near the media that describes or transcribes the content
• Verify that any spoken information in video is available in another form

Common Scenarios:

• Training videos with narration but no captions
• Audio interviews without transcripts
• Video demonstrations where spoken instructions are not in text
• Promotional videos with voiceovers but no subtitles

05-002: Audio Annotation Present Without Alternative (Human Testing)

What's Wrong: An audio annotation is attached to a document element (such as a note or comment), but the content of that audio is not available in text form. Audio annotations are different from media annotations; they are typically shorter clips attached to specific locations in the document.

How to Identify:

• Check the Comments panel for any audio comments
• Look for speaker icons that indicate attached audio
• Play any audio annotations
• Verify that a text equivalent exists for each audio annotation
• Check whether the audio adds information not available elsewhere

Common Scenarios:

• Voice comments instead of text comments
• Audio instructions attached to form fields
• Spoken annotations on reviewed documents
• Audio explanations for complex content

05-003: JavaScript Beep Without Visual Notification (Human Testing)

What's Wrong: JavaScript in the PDF uses the beep function to alert users, but no visual indication accompanies the sound. Users who cannot hear the beep receive no notification.

How to Identify:

• Test all interactive elements in the PDF
• Fill out forms and trigger validation
• Complete actions that might generate alerts
• Watch for both audio beeps and visual indicators
• Check whether every beep is accompanied by a visual change (color, text message, icon)
• Review JavaScript code if accessible for app.beep() calls

Common Scenarios:

• Form validation that only beeps on errors
• Calculation alerts without visual confirmation
• Timer warnings with audio-only notification
• Button actions with sound-only feedback

How to Fix in Adobe Acrobat

Adobe Acrobat provides tools for managing multimedia content and adding text alternatives.

Identifying Media Content

1. Open your PDF in Adobe Acrobat Pro
2. Go to Tools > Rich Media
3. Look for any embedded audio or video content
4. Click on each media element to review it
5. Check whether captions or transcripts already exist

Adding Captions to Video

If you have video with audio that lacks captions:

1. Best option: Edit the original video file

   • Use video editing software to add burned-in captions
   • Or add closed caption tracks (SRT, VTT files)
   • Re-embed the captioned video

2. Alternative: Add a transcript alongside the video

   • Create a text transcript of all spoken content
   • Add the transcript as text in the PDF near the video
   • Tag the transcript appropriately and link it to the video

Adding Transcripts for Audio

1. Create a complete transcript of the audio content
2. Include speaker identification where relevant
3. Note significant non-speech sounds (music, effects)
4. Add the transcript to the PDF:
   • Place text near the audio player
   • Or create a separate section with the transcript
5. Tag the transcript as regular content (P, Span)
6. Consider adding a link from the audio to the transcript

Fixing Audio Annotations

1. Go to View > Show/Hide > Navigation Panes > Comments
2. Identify any audio comments
3. For each audio comment:
   • Play the audio and note the content
   • Add a text comment with the same information
   • Delete or keep the audio version as supplementary

Addressing JavaScript Beeps

1. Go to Tools > JavaScript
2. Select Document JavaScripts
3. Review scripts for app.beep() calls
4. For each beep, add a visual notification:

Example modification:

// Instead of just:
app.beep();

// Add visual feedback:
app.beep();
app.alert("Validation error: Please check the highlighted fields", 1);
// Or update a form field to show the error
this.getField("errorMessage").value = "Error: Invalid input";

Using Alternative Visual Alerts

Replace or supplement audio alerts with:

1. Alert dialogs: app.alert() displays a message box
2. Field highlighting: Change field borders or colors
3. Status text: Update a text field with the message
4. Icon changes: Show/hide error indicator images

How to Fix in Microsoft Word

When creating source documents in Word, plan for accessible audio alternatives from the start.

Avoiding Audio-Only Content

1. Do not embed audio files without transcripts
2. If including video, ensure captions exist before embedding
3. Write text descriptions for any audio content

Adding Transcripts for Multimedia

1. Create a complete transcript before embedding media
2. Format the transcript appropriately:
   • Use heading styles to introduce the transcript
   • Use paragraph styles for the content
   • Include timestamps if helpful
3. Place the transcript near the embedded media
4. Add a note explaining that the transcript is available

Best Practices for Video in Word

1. Caption your videos before embedding:

   • Use YouTube, Vimeo, or video editing software to add captions
   • Download the captioned version for embedding

2. Provide multiple formats:

   • Embedded video with captions
   • Link to external video with caption options
   • Full text transcript in the document

3. Check video accessibility:

   • Ensure captions are accurate
   • Verify caption timing
   • Include speaker identification
   • Describe significant visual content for comprehensive accessibility

PDF Export Considerations

1. When exporting to PDF, multimedia handling varies by method
2. Test the resulting PDF for:
   • Proper media embedding
   • Caption visibility and function
   • Transcript accessibility
3. You may need to add alternatives after PDF creation in Acrobat

Testing Your Fix

Because sound-related violations require human testing, verification must be thorough and systematic.

Manual Audio Review

1. Play all audio and video content in the PDF
2. For each piece of audio content, verify:
   • A transcript or caption exists
   • The alternative contains the same information
   • The alternative is accessible (properly tagged)
   • The alternative is easy to find near the audio content

Testing Without Sound

1. Mute your computer speakers
2. Navigate through the entire PDF
3. Interact with all forms and buttons
4. Verify you can:
   • Understand all content without audio
   • Receive all alerts and notifications visually
   • Complete all tasks without hearing anything

Screen Reader Testing

1. Open the PDF with a screen reader (NVDA, JAWS, VoiceOver)
2. Navigate to multimedia content
3. Verify:
   • The screen reader announces the presence of media
   • Transcripts are readable by the screen reader
   • Alternative text describes what the media contains
   • No information is trapped in audio-only format

JavaScript Alert Testing

1. Enable JavaScript in your PDF reader
2. Test all interactive elements:
   • Submit forms with invalid data
   • Trigger any calculation functions
   • Complete any scripted workflows
3. Note every audio alert
4. Verify each alert has a visual equivalent
5. Test with speakers off to confirm visual alerts work alone

Transcript Quality Checklist

For each transcript, verify:

• All spoken content is included
• Speaker changes are identified
• Significant sounds are described (music, applause, etc.)
• Technical terms are spelled correctly
• The transcript is placed near the audio content
• The transcript is properly tagged for accessibility
• Timestamps are included if content is time-sensitive

Validation Checklist

• All media annotations have transcripts or captions
• All audio annotations have text equivalents
• All JavaScript beeps have visual alternatives
• Transcripts contain equivalent information
• Alternatives are accessible to assistive technology
• Document is fully usable without sound

Additional Resources

Official Standards and Guidelines

• W3C WCAG 2.1 Success Criterion 1.2.1: Audio-only and Video-only (Prerecorded)
• W3C WCAG 2.1 Success Criterion 1.4.2: Audio Control
• PDF Association Matterhorn Protocol 1.02

Captioning and Transcription

• W3C Web Accessibility Tutorials: Captions/Subtitles
• Described and Captioned Media Program
• 3Play Media: Complete Guide to Closed Captioning

Tools and Services

• YouTube Auto-Captions - Auto-generate captions (requires review)
• Otter.ai - AI-powered transcription service
• Rev - Professional transcription and captioning
• Descript - Audio/video editing with transcription

Accessibility Testing

• PAC (PDF Accessibility Checker) - Free PDF/UA validation
• NVDA Screen Reader - Free screen reader for testing
• WebAIM: Creating Accessible Media

This documentation is based on the Matterhorn Protocol 1.02, the definitive reference for PDF/UA validation. Sound-related violations require human testing because automated tools cannot analyze audio content or verify the completeness of alternatives. For the most current information, consult the PDF Association and W3C WCAG guidelines.