AVSpeechUtterance with Dutch AVSpeechSynthesisVoice glitches on some words

Number:rdar://FB9144292 Date Originated:Jun 9, 2021 at 10:54 AM
Status:Open Resolved:
Product:AVFoundation Product Version:Tested with iOS 14.4 and iOS 14.6
Classification:Incorrect/Unexpected Behavior Reproducible:Yes
In our app we use AVSpeechSynthesizer to speak navigation directions. Our Dutch users notice that many of the utterances glitch, where it seems to speak a random '-' in-between the text. 

This is reproducible by simply speaking this text on a Dutch AVSpeechSynthesisVoice:  "Over 300 meter houd rechts aan richting Breda." (which means "In 300 meters, keep right towards Breda."). It glitches on the word 'aan'. 

Reproducible only on-device, as the Xcode simulator doesn't seem to have this issue. Tested on iOS 14.4 and 14.6, where both have this issue. Attached is a small project that reproduces the issue when run on-device and pressing the button on-screen. The issue is very obvious to hear. 

Texts that also have this issue: 
- "Over 900 meter houd rechts aan en blijf op Muntweg."
- "Houd rechts aan."


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