• In the Waveform Editor, choose Edit > Convert Sample Type. or Shift T.
  • From the Channels menu, select Mono

    Adobe Audition

    Convert Sample Type

  • In the Advanced section, Enter percentages for Left Mix and Right Mix.
    • When you convert from mono to stereo, the Left Mix and Right Mix options specify the relative amplitude with which the original mono signal is placed into each side of the new stereo signal. For example, you can place the mono source on the left channel only, the right channel only, or any point in between.
    • When you convert from stereo to mono, the Left Mix and Right Mix options control the amount of signal from the respective channel that will be mixed into the final mono waveform. The most common mixing method uses 50% of both channels.

    Info found on the Adobe Website.