Try adding
log_user 0
to your script. That should turn off the display to stdout.
If you want to turn it on again for the "do some thing" part of the program, re-enable it
log_user 1
using this command:
exec >log 2>&1
you can forward your output to a file or you can pass it to dev/null
is with -stty and stty
stty -echosend_user "Password: "expect_user -re "(.*)\n"set password $expect_out(1,string)stty echo