Question: what is the sound generated by backflow through a valve
[{'answer': 'Abnormal murmurs', 'provenance': [{'wikipedia_id': '237412', 'title': 'Heart sounds', 'start_paragraph_id': 4, 'start_character': 555, 'end_paragraph_id': 4, 'end_character': 571, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '237412', 'title': 'Heart sounds', 'start_paragraph_id': 4, 'start_character': 0, 'end_paragraph_id': 4, 'end_character': 973, 'bleu_score': 0.9713492876971751, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15787576522402191971}, 'section': 'Section::::Abstract.'}]}]