i think its also very likely the brake pads that stop the blades from spinning when you disengage the blades, are worn right through to the metal backing.
its very common
to test this, with mower off, engage the blades, this releases pressure on the brake pads, then spin the blades by hand (very carefully) and see if its still making noise. inmost cases if the spindle bearing are bad enough to hear noise over sound of engine then its so loose its flopping around in the hole