The U.S. Justice Department has closed an investigation into the audio headset maker Plantronics Inc. without criminal prosecution, citing the company’s “full cooperation” with a foreign bribery investigation involving a communications technology firm that it acquired this year.

In settlements with the DOJ and U.S. securities regulators, the Santa Cruz, California-based company agreed to pay $36 million to resolve allegations involving Polycom, which Plantronics acquired in July. Plantronics, represented by Foley & Lardner and Wilson Sonsini Goodrich & Rosati, said the alleged misconduct predated its $2 billion acquisition of Polycom and that all of the Polycom employees involved had left the company by the time the deal closed in July.