alarms, beeps and voice

The below is available in R's base package as a notification method, for example, to alert users that a long running script has finished.

alarm()

'beepr' package is available to provide more options for notification sounds

install.packages("beepr")
library(beepr)
beep()
beep(1)
beep(2)
beep(3)
.
.
.

In Mac, text to speech technique can be called from R

system("say Loop 1 completed")

for different voice options

system("say -v Tessa Loop 2 completed")