Text-to-Speech Deep Dive

Overview

Text-to-Speech (TTS) converts written text to spoken audio with synchronised word highlighting. This deep dive covers all available settings and use cases.

Who benefits most: Students with dyslexia, visual processing difficulties, attention challenges, or anyone who learns better by listening.

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All Settings Explained

Voice Selection

Choose from voices available on your system:

Setting	Options	Default
Voice	System voices (varies by OS)	System default

Finding voices:

• Windows: Settings → Time & Language → Speech
• Mac: System Preferences → Accessibility → Spoken Content
• Chromebook: Settings → Accessibility → Text-to-Speech

Tips:

• Some voices sound more natural than others
• Try several voices to find one you like
• Download additional voices from your OS settings

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Speed Controls

Setting	Range	Default	Description
Rate	0.5x - 2.0x	1.0x	How fast text is read
Pitch	0.5 - 2.0	1.0	Voice pitch (higher/lower)
Volume	0 - 100%	100%	TTS audio volume

Speed recommendations:

User Need	Recommended Speed
Learning new content	0.8x - 1.0x
Familiar content review	1.2x - 1.5x
Proofreading own work	0.7x - 0.9x
Language learners	0.6x - 0.8x

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Word Highlighting

Setting	Options	Default
Highlight enabled	On/Off	On
Highlight colour	Colour picker	Yellow (#FFEB3B)
Highlight opacity	10% - 100%	70%
Word-by-word	On/Off	Off
Sentence highlighting	On/Off	Off

Highlighting modes:

Mode	How It Works	Best For
Word-by-word	Highlights each word as spoken	Following along closely
Sentence	Highlights whole sentence	Faster readers
Both	Word highlighted within sentence	Maximum tracking

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Reading Scope

Controls how much of the page TTS reads in a single playback session.

Setting	Options	Default
Reading Scope	Paragraph / Section / Whole Page	Paragraph

Option	Behaviour
Paragraph	Reads the paragraph containing the cursor, then stops
Section	Reads from the cursor to the end of the current heading section
Whole Page	Reads all readable content on the page from start to finish

Tip: Use Paragraph for focused reading, Whole Page for hands-free listening while you do something else.

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Word Highlight Sync Mode

Controls how word highlighting stays in sync with the voice.

Setting	Options	Default
Sync Mode	Boundary / Timer	Boundary

Option	How It Works
Boundary	Highlights update on boundary events fired by the speech engine — accurate but dependent on browser voice support
Timer	Highlights advance on a fixed timer — more consistent across voices that don’t fire boundary events reliably

Tip: If word highlights seem out of sync with the voice, switch to Timer mode.

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Word Highlight Speed

Adjusts the timer cadence when Timer sync mode is active.

Setting	Range	Default
Highlight Speed	0.5× – 4×	2×

Higher values advance highlights faster. Match this to your TTS speed for best results.

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Reading Behaviour

Setting	Options	Default
Read from cursor	On/Off	On
Auto-scroll	On/Off	On
Skip headings	On/Off	Off
Skip links	On/Off	Off
Announce punctuation	On/Off	Off

Read from cursor: When enabled, TTS starts reading from wherever you click on the page rather than the beginning.

Auto-scroll: Page scrolls automatically to keep the highlighted text visible.

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Step-by-Step Setup

Basic Setup

1. Click AssisT icon in toolbar
2. Expand Reading Help section
3. Toggle Text-to-Speech ON
4. Test with Ctrl+Shift+Space on any page

Optimised Setup for Different Needs

For dyslexia:

1. Enable word-by-word highlighting
2. Set speed to 0.8x - 1.0x
3. Choose high-contrast highlight colour (yellow or green)
4. Enable sentence highlighting as well

For ADHD:

1. Enable auto-scroll
2. Set speed to 1.0x - 1.2x
3. Enable read-from-cursor
4. Choose a bright highlight colour

For language learning:

1. Set speed to 0.6x - 0.8x
2. Enable word highlighting
3. Choose a clear, natural voice
4. Enable announce punctuation

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Common Use Cases

Proofreading Your Own Writing

Settings:

• Speed: 0.7x - 0.9x (slower catches errors)
• Highlighting: Word-by-word
• Read from cursor: On

How it helps: Hearing your writing read aloud reveals awkward phrasing, missing words, and repetition that your eyes skip over.

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Studying Long Documents

Settings:

• Speed: 1.0x (adjust to comfort)
• Auto-scroll: On
• Sentence highlighting: On

How it helps: Reduces eye fatigue, allows multitasking (follow along or listen only), and provides dual-channel learning (visual + auditory).

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Reading Before Sleep

Settings:

• Speed: 0.8x
• Volume: 50-70%
• Highlighting: Off (screen off)

How it helps: Listen without screen light. Combine with a Screen Color Overlay or turn screen off entirely.

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Following Along with Physical Text

Settings:

• Speed: 0.9x - 1.0x
• Highlighting: Off
• Read from cursor: On

How it helps: Use TTS as audio guide while reading printed textbook. Pause and resume as needed.

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Troubleshooting

No Sound Playing

Solutions:

1. Check system volume isn’t muted
2. Verify TTS is enabled in AssisT popup
3. Try a different voice in settings
4. Check Chrome sound permissions for the website
5. Restart Chrome

Voice Sounds Robotic

Solutions:

1. Download better voices from OS settings
2. Try different available voices
3. Adjust pitch setting slightly (0.9 or 1.1)
4. On Windows: Install neural voices from Settings

Highlighting Not Working

Solutions:

1. Verify “Highlight enabled” is on in settings
2. Check if page uses unusual text rendering
3. Try refreshing the page
4. Some PDFs may not support highlighting

TTS Stops Unexpectedly

Solutions:

1. Page may have lost focus — click back on page
2. Content may have ended — select new content
3. Try pressing Ctrl+Shift+Space to resume
4. Refresh page if problem persists

Wrong Language Being Used

Solutions:

1. Text may be in different language than expected
2. Manually select voice that matches content language
3. Some voices only support specific languages

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Equations (Preview)

By default a maths equation in the page is either skipped or read out as a run of symbols, which tells a listener almost nothing. With the Equation read-aloud companion feature on, equations join the ordinary reading flow instead: they are spoken as maths, in sequence with the surrounding sentences, and the synchronised highlight tracks through them the way it tracks through text.

It is on by default. Its switch is in the popup under Companion (preview), and it is marked preview because it is newer than the rest of the extension and is still being refined.

Maths Support, in the Reading group, is the related setting for reading numbers on the page and for the on-page calculator.

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Mind Maps

Read aloud also works inside the mind map editor. Alt+R speaks a branch using the same voice, rate and pitch you set here, and highlights the node being read. See the Mind Map guide.

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Keyboard Shortcuts

Shortcut	Action
Ctrl+Shift+Space	Play/Pause TTS
Ctrl+Shift+S	Stop TTS

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For Educators & Parents

Setting Up TTS for Students

1. Test voice options together — Student preference matters
2. Start with defaults — Adjust only if needed
3. Set appropriate speed — Slower for new content, faster for review
4. Enable highlighting — Visual tracking helps most learners

Monitoring Usage

TTS doesn’t track or report usage. To check if students are using it effectively:

• Ask students to demonstrate their settings
• Observe during study sessions
• Check if comprehension improves with TTS use

Classroom Implementation

• TTS works on most educational websites
• Compatible with Canvas, Moodle, Google Classroom
• Works offline once page is loaded
• No additional logins or accounts needed

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Related Features

• Reading Help — TTS overview
• Dyslexia Reading Modes — Combine with TTS
• User Profiles — Pre-configured TTS profiles