Install Praat software from http://www.fon.hum.uva.nl/praat/
/usr/bin/praat (directory of the script)/speechRate.praat -15 3 0.3 yes (directory of the input wav files)
Eg. /usr/bin/praat /home/aswin/Work/Badiyajobs/Rate\ of\ Speech/speechRate.praat -15 3 0.3 yes /home/aswin/Downloads/voice_rec/edited/