'sox' is not recognized as an internal or external command, operable program or batch file.

[ChernobylGum]

Hello,
Can anyone please help with this

When I run convert_directory.py I get the error message:

'sox' is not recognized as an internal or external command,
operable program or batch file.
'sox' is not recognized as an internal or external command,
operable program or batch file.
Flushing to disk...
C:\Python27\lib\site-packages\numpy\core\fromnumeric.py:3118: RuntimeWarning: Mean of empty slice.
out=out, **kwargs)
C:\Python27\lib\site-packages\numpy\core_methods.py:78: RuntimeWarning: invalid value encountered in true_divide
ret, rcount, out=ret, casting='unsafe', subok=False)
Done!

Thanks in advance.