US Patent # 9,485,982
Date: 11/8/2016 - Game call with a single mouthpiece and a body with multiple passages of different shapes or sizes associated with different airflow resistances.
US Patent # 8,727,828
Date: 5/20/2014 - Game call with an inlet, a splitter with at least one outlet, and multiple pipes of different lengths, wherein at least one of the pipes is connected to the outlet of the splitter.
US Patent # 8,016,637
Date: 9/13/2011 - Method of reproducing animal voice using a game call with an air inlet, splitter w/ multiple passages, and resonance chambers (e.g., extension pipes).
US Patent # 7,465,213
Date: 12/16/2008 - Game call with a single air inlet and splitter w/ multiple passages.