A fuel nozzle assembly for a gas turbine engine includes a flange and a pre-mix tube. The flange includes a first end that is configured to couple to an end cover of the combustor, and a second end that is opposite said first end. The pre-mix tube is coupled at a first end to the flange second end. The flange and the pre-mix tube are fabricated to operate at a natural frequency that is different from an operating frequency of the gas turbine engine.