Low noise turbine for geared gas turbine engine

A gas turbine engine comprising:

• a propulsor section including a propulsor having a propulsor rotor and a plurality of propulsor blades;
• a geared architecture;
• a high spool including a high pressure compressor, a high pressure turbine and an outer shaft that connects the high pressure compressor and the high pressure turbine;
• a low spool including a low pressure compressor, a low pressure turbine and an inner shaft that connects the propulsor and the low pressure compressor to the low pressure turbine, wherein the inner shaft drives the propulsor through the geared architecture, the low pressure turbine includes at least three turbine rotors, the high pressure turbine includes two stages, and the inner and outer shafts are concentric and rotate via bearing systems about an engine central longitudinal axis;
• and
• wherein at least one stage of the low pressure turbine includes an array of rotatable blades and an array of vanes, the array of vanes of the at least one stage are immediately upstream or downstream from the array of blades, a ratio of the number of vanes to the number of blades of the at least one stage is greater than or equal to 1.55, and a mechanical tip rotational Mach number of the array of blades is greater than or equal to 0.5 at an approach speed, the approach speed taken at an approach certification point as defined in Part 36 of the Federal Airworthiness Regulations.