Audio Cleanup and Voice Enhancement

I need an experienced audio engineer to clean up a low-quality audio file. This is part of an ongoing confidential investigation, with more files to follow.

Requirements:
- Remove human-made background noise (e.g., chatter, machinery)
- Enhance voice by improving volume and clarity

Ideal skills and experience:
- Proficiency in audio editing software (e.g., Audacity, Adobe Audition)
- Experience with noise reduction and voice enhancement techniques
- Attention to detail and ability to handle confidential material

Please provide samples of previous work.