Here's the WEB page for my SONAR SF05.

http://www.robot-electronics.co.uk/htm/srf05tech.htm

It says:
-10microsec trigger pulse
-produces an 8 cycle burst of 40khz sound (total duration 5millisec)
-can be triggered every 50millisec (20 per second)
-the beam pattern is conical.

Details! Details! Ain't technology grande!
Ken