need some help with adjusting recording

[fairlanemama]

I am a court reporter and recently took a video deposition. The videographer ran a line from his equipment directly to a USB mic on my computer. The recording is SOOO loud and garbly. I have WavePad and have tried to amplify to half volume and spectral subtraction, but I'm not having very good luck. I am wondering if someone can give me a few suggestions to lower the entire recording and stop the garbly/vibrating sound of it.

 

Thanks much,

Karen