We all saw Hawaii was doing this a lot and if definitely disrupted Cardale the 1st few possessions, but the refs didn't do anything and the announcers said it wasn't against the rule.  I thought it was bush league and a little dirty.

This morning a googled it and this is what I found:

Rule 7, Section 1, Article 5, Subpart A states: “No player shall use words or signals that disconcert opponents when they are preparing to put the ball in play. No player may call defensive signals that simulate the sound or cadence of (or otherwise interfere with) offensive starting signals. An official shall sound his whistle immediately.”