Usher was targeted by a crazed fan while taping The Voice on Thursday (18 April).
An unidentified woman in the audience was eventually kicked out of the studio after constantly screaming Usher's name and blowing a whistle.
A source told the New York Post's Page Six that the fan was initially asked to calm down after she repeatedly "blew a whistle" in a bid to distract the More singer, but after she "refused" to stop, a security guard removed her from the NBC studio.
The insider said: "The woman was blowing her whistle and yelling Usher's name."
Another source said that the woman kept "pointing at Usher and exclaiming, 'I want you!'" repeatedly, adding: "The security people escorted her out to the street."
Usher took the incident in his stride and the show continued.
The source explained: "It was at the end of the first half of the day, right before lunch, so taping was not delayed."
This season's panel of judges also includes Adam Levine, Shakira and country music star Blake Shelton.