This "real" is the question, what kind of ontological position (way of existing) is this effect. Is the effect like a mountain or a tree? pain? beauty? good? logic? math?
The realness hasn't been able to be demonstrated and proved simply by pointing to it and saying, "see there it is."
The effect would be a perception of the listener. You would likely use a diary based test survey with an agreed upon scale. You would need a large sample size. But you could fail to reject that they are different. This would make the perceived, real or at least not being random chance.
This is done with allergy patients to assess symptoms instead of directly measuring inflammation or nasal airway caliber. They are noisy because symptoms are qualitative measures but they are a perfectly valid means of evaluating something. Good enough for FDA however may not be good enough for Headfi...:-)