uncaptcha
Defeating Google's audio reCaptcha with 85% accuracy
...It employs signal processing techniques such as segmenting audio clips into individual components before transcription, which improves accuracy in noisy or complex audio conditions. The project was developed as part of academic research to highlight potential weaknesses in CAPTCHA systems and includes disclaimers emphasizing responsible use. While it achieved high success rates at the time of publication, later updates to reCAPTCHA have reduced its effectiveness.