A good number of Audio files are freely downloadable. Few of them listed below:

1 Classroom Audio (Business Plus Level 1 Student's Book)
Audio, 63mb

2 Classroom Audio (Business Plus Level 2 Student's Book)
Audio, 59mb

3 Classroom Audio (Business Plus Level 3 Student's Book)
Audio, 67mb

6 - 7 Classroom Audio (Objective IELTS Advanced Audio)
Audio, 174mb