EAST LANSING, Mich. — An emergency siren blared on Michigan State University’s campus in late January, turning the heads of a few students milling along the web of sidewalks behind Wells Hall, just south of the Red Cedar River. The Jan. 23 alert was a test run conducted by the university’s Department of Police and Public Safety, which is honing the outdoor signal as a communication tool that could be used during a mass shooting like the one that unfolded on campus last year. Whether the siren caught students’ attention was hit and miss. John Eidt, a freshman from Bloomfield Hills, did not hear…