Left channel has more noise than right channel.

1) mp4: extract to wav file [A]

Audacity:

2) [A] -> [B] 
  - AudioTrack: Split Stereo to Mono, drop right channel 'mono'
  - Effect.Inverter

3) [A] -> [C] 
  - Tracks: Stereo Track to Mono
  - Audio Track: Amplify +2dB (simply use slider)

4) [B] + [C] -> [D]
  - Tracks: Mix and Render

5) [D] -> [E]
  - Effect.Noise_Removal..
    - Pick short noise sample
    - Remove noise:
      - Noise reduction -10 dB, 
        Sensitivity 0dB, 
        Frequency smoothing 300Hz, 
        Attack/decay time 0.15s

6) [E] -> [F]
    - Effect.Compressor
      - Threshold -16 dB
        Noise Floor -30 dB
        Ratio 2:1
        Attack Time 0.2s
        Decay Time 1.0s
        Gain for 0dB: ON
        Compress based on Peaks: ON