PronDifficulty

A rule-based system for evaluating pronunciation difficulty of words across multiple languages.

Features

• Supports English (en), Norwegian Bokmål (nb), Spanish (es), and Italian (it)
• Provides difficulty scores from 0 (easiest) to 1 (hardest)
• Analyzes multiple linguistic aspects:
  • Phoneme complexity (40%)
  • Maximum phoneme difficulty (20%)
  • Syllable structure (20%)
  • Phonotactic constraints (10%)
  • Prosodic patterns (5%)
  • Complex phoneme ratio (5%)

Installation

pip install pron-difficulty

Quick Start

from pron_difficulty import PronDifficulty

evaluator = PronDifficulty()

# Single word evaluation
score = evaluator.evaluate("difficult", "en")
print(f"Difficulty score: {score}")  # Example: 0.723

# Batch evaluation
words = ["cat", "difficult", "antidisestablishmentarianism"]
scores = evaluator.evaluate_batch(words, "en")

How It Works

The system analyzes pronunciation difficulty through several components:

1. Phoneme Complexity (40%)

• Evaluates individual sound difficulty
• Considers articulatory features (place, manner, voicing)
• Rates rare or complex phonemes higher (e.g., /θ/, /ð/ in English)

2. Maximum Phoneme Difficulty (20%)

• Tracks the hardest sound in the word
• Helps identify words with even one challenging phoneme
• Example: "th" in "think" increases difficulty even if rest is simple

3. Syllable Structure (20%)

• Analyzes consonant clusters (e.g., "str" in "string")
• Evaluates syllable patterns (CV, CVC, CCVC, etc.)
• More complex structures = higher scores

4. Phonotactic Constraints (10%)

• Checks if sound combinations follow language rules
• Penalizes unusual or forbidden sequences
• Example: "ng" at start of word (uncommon in English)

5. Prosodic Structure (5%)

• Examines rhythm and stress patterns
• Analyzes sonority profiles
• Considers length and complexity of prosodic units

6. Complex Phoneme Ratio (5%)

• Percentage of difficult phonemes in word
• Helps differentiate consistently hard words
• Affects longer words more significantly

Length Scaling

Words get additional difficulty points based on length:

• ≤3 phonemes: no extra points
• 4-6 phonemes: +0.2 per extra phoneme
• > 6 phonemes: +0.1 per extra phoneme (max 0.7)

Final Score Adjustment

• Simple words (score < 0.4): Gentle sigmoid curve
• Complex words (score ≥ 0.4): Steeper sigmoid + exponential boost for very complex words

Language Support

Each supported language has:

• Custom phoneme difficulty ratings
• Language-specific syllable patterns
• Tailored phonotactic rules
• Adjusted prosodic analysis

Examples with Explanations

# English examples with typical scores:
"cat" -> 0.123         # Simple CV-C structure, common phonemes
"string" -> 0.567      # Complex onset cluster, but common in English
"rhythm" -> 0.789      # Unusual consonant patterns, no vowel between 'th' and 'm'

# Norwegian examples:
"hei" -> 0.234        # Simple structure, common sounds
"skjønnhet" -> 0.678  # Complex consonant cluster, front rounded vowel

# Spanish examples:
"casa" -> 0.123       # Simple CV-CV structure
"desarrollo" -> 0.456 # Longer but regular structure

# Italian examples:
"ciao" -> 0.234       # Simple structure despite diphthong
"struggere" -> 0.567  # Complex consonant cluster

Contributing

Contributions welcome! Areas for improvement:

• Additional language support
• Refined difficulty metrics
• Enhanced prosodic analysis
• Performance optimizations

License

This project is licensed under the European Union Public Licence (EUPL) v. 1.2. See the LICENSE file for details.