The author of the NewPing library has provided an explanation and suggestions for fixing this error:
https://bitbucket.org/teckel12/arduino-new-ping/wiki/Multiple%20Definition%20of%20"__vector_7"%20Error
The author of the NewPing library has provided an explanation and suggestions for fixing this error:
https://bitbucket.org/teckel12/arduino-new-ping/wiki/Multiple%20Definition%20of%20"__vector_7"%20Error