Replace the current jarring sound alerts with smoother, more pleasant
bell-like tones inspired by voice assistants like Siri and Gemini.
Changes:
- start_recording.wav: Ascending perfect fifth (A4→E5, 0.30s)
- stop_recording.wav: Descending perfect fifth (E5→A4, 0.25s)
- error.wav: Low gentle chime (E4, 0.35s)
Technical improvements:
- Smooth frequency sweeps (sigmoid curve transitions)
- Subtle vibrato (8Hz) for warmth and richness
- Harmonic overtones for fullness
- Elegant exponential decay envelopes
- Reduced file sizes (926KB → 80KB total)
The new sounds are shorter (0.25-0.35s vs 0.5-1s), quieter
(20-25% amplitude vs full volume), and more pleasant for frequent use.
