In Arizona, our criminal and civil rules of procedure allow jurors to communicate during the trial through written questions. 

Jurors are given instructions "jury instructions" from the court at the beginning of the trial immediately after the jury is sworn. These instructions include, among other things, the duties, conduct and order of proceedings, the procedure for submitting written questions of witnesses or of the court, and basic legal principles that will govern the proceeding. (Arizona Rules of Civil Procedure Rule 39(b)) and (Arizona Rules of Criminal Procedure Rule 18.6)

Typically, if a juror has a question during the trial, the question is written down by the juror and handed to the bailiff. The judge will then review the question with the attorneys for each party and the attorneys may object to the question outside the presence of the jury. Objections are usually made if the question is not a permissible question under the rules of evidence. If the judge sustains (accepts) the objection then the question is not allowed. This is really the only way a juror may "speak up" during a trial.

Jurors are also given an "admonishment" at the beginning of the trial that they are not allowed to speak about the trial until AFTER the trial. This process is supposed to protect the parties on trial so the jurors are not influenced during the trial by outside sources. (Arizona Rules of Civil Procedure Rule 39(f))