What is the test for inferring that a defendant's absence from a criminal proceeding is voluntary?

Under Arizona's rules of criminal procedure, the court may infer an absence is voluntary if the defendant had personal notice of (1) the time of the proceeding, (2) his right to be present at it, and (3) a warning that the proceeding would go forward in his absence should he fail to appear. Ariz.R.Crim.P. 9.1. We have held that Rule 9.1 "comports with the requirements of a waiver of the defendant's constitutional rights provided that the defendant is afforded a hearing to determine whether his absence was, in fact, voluntary." Brewer v. Raines, 670 F.2d 117, 120 (9th Cir.1982).