Resolved

Keystroke audio plays robotic brrr sound for consecutive spaces after shift chars

Python
Audio Processing
Debugging
State Management
Algorithm
Text Processing
Sound Synthesis
Performance

Python keystroke sound generator incorrectly played multiple space sounds after shift characters like quotes and brackets | Created machine-gun 'brrr' effect instead of natural single space sound

Working with a Python-based keystroke sound generation system, the system synthesized typing sounds from text input, handling character timings and triggering corresponding audio samples, including special handling for spaces and shift characters.

Issue

The keystroke audio generator produced an unnatural ‘brrr’ machine-gun effect when processing consecutive spaces after shift characters (e.g., quotes, parentheses, brackets). While code indentation spaces worked correctly (single sound), spaces following shift characters caused the system to play multiple space sounds (e.g., 4 sounds for " (hello) " instead of the expected 2), creating robotic audio artifacts.

Culprit

The root cause was a broken state tracking mechanism in the prev_char variable used for consecutive space detection. During processing of shift characters or non-keystroke sequences, the system updated prev_char without correctly handling the space detection chain. This resulted in incorrect deduplication of spaces, especially when processing sequences like:

"  (hello)  "

The logic failed to recognize consecutive spaces due to gaps in state tracking caused by skipping non-keystroke characters.

Solution

Stateless Look-Ahead Approach

Replaced the stateful prev_char tracking with a stateless look-ahead approach using pre-calculated space indices:

  1. Pre-processing Phase: Identified all space indices in the input text during a one-time pass.
  2. Look-Ahead Deduplication: Used set-based lookups to skip redundant space sounds when consecutive spaces were detected.

Key Improvements:

  • Stateless: Eliminated cross-iteration variable tracking, improving reliability.
  • Robust: Worked uniformly across all space sequences, regardless of preceding characters.
  • Efficient: Utilized set lookups for fast deduplication.
  • Consistent: Ensured uniform behavior for spaces in code, around shift characters, and in mixed sequences.

The solution improved the system’s handling of spaces following shift characters, ensuring natural audio output without robotic artifacts. Testing confirmed correct behavior for:

  • Spaces around shift characters: " (hello) " → 2 sounds.
  • Code indentation: → 1 sound.
  • Mixed sequences: def foo(): → 1 sound.
  • Complex sequences involving shift/alt characters.

This approach resolved the unnatural ‘brrr’ effect and ensured consistent audio output across all scenarios.