Invalid Sample Rate for Batch Processing

Audacity 2.4.2 on Windows 10.
My macro has one command: ExportMP3
I’m batch processing sermon and lecture audios to reduce their size.
But as each file is processed, I get the following error.

Invalid Sample Rate
The project sample rate (44100) and bit rate (16 kbps) combination is not supported by the MP3 file format. You may resample to one of the rates below.
Sample rates: 8000

Selecting 8000 yields a good result for my purposes. How do I set it permanently to avoid the above error?
I tried changing Project Rate (Hz) in lower right corner to 8000 but the error still occurs and it resets to 44100 for each file.

Thank you.

P.S. My ExportMP3 settings are as follows.

  • Bit Rate Mode: Constant
  • Quality: 16kbps
  • Variable Speed: Standard
  • Channel Mode: Joint Stereo

That’s very low quality. Are you sure you want such poor audio quality?
If you do, then you will need to add a “SetProject:” command to your macro to change the Project Rate prior to the Export step.

Thank you.
After adding the following as the first command:
Set Project Rate=“8000”
The batch processing works perfectly.