Why do intelligent people deny audio differences?

We are all human and we all have ego. The ego wants above all control, and cling to what can be seen, touch and explained. Our minds are comfortable only in the security of the known. That which cannot be fathomed is simply too scary for the ego to entertain in its limited world view.

Our culture, the educational system reinforced this tendency. We tend to equate intelligence with a logical mind and sensibility, and dismiss our intuitive and creative faculty. In the process we lost awe of the mysteries of life and a large part of our true capactiy laid dormant. We are taught to think in acceptable norms of the society, and that fleeting voice of the heart are not trusted.

The ego's identification with control and what can be known is the reason why the subject of death is treated as much of a taboo. I draw on Rodney Smith:

"Consider the question of what it means to be human. Birth and death are the boundaries of our known existence and embody the enigma of life. We atempt to understand who we are and investigating where we came from and where we are going. This is one of the reasons that death holds such a fascination for us. By approaching it we hope to gain insight into our real nature, but that nature is as unfathomable as death itself. So the mind works to make death understandable even as our hearts delight with the impossibility of the task."

The ironic thing is when the world view is fragmented, life has a way of forcing a balance upon it. Often we appreciate this too late.

This is an intriguing topic for me, not least because of a recent incidence. A couple of weeks ago I was selling over head-fi my Grado RS2i headphone, a much sought after item, to a gentleman in Sweden. On my way to the post office I got a vague hunch that I should cancel the transaction, but because the Swedish gentleman has already paid then I did not heed my intuition and went ahead and shipped the parcel to Sweden. Not long thereafter I received an email from the buyer that he received the parcel but was forced to pay heavy custom duties because I have specified the value of the phone on the accompanying shipping documents. I wasn’t conscious of the issues because I shipped like these from my country to the US many times without problem. To pacify the Swedish gentleman I made a refund to him, so that the net price was such that I would never have sold the phones at such low price. I told the Swedish gentleman what happened, and that the refund was my tuition fees for not listening to that fleeting inner voice. He wrote me back “you should always listen to your intuition”.

Now this incidence seemingly has no bearing to the OP’s question of why do intelligent people deny audio differences, but I do see a correlation. I guess sooner or later one would come across people who insist only upon the measurable, logical, the calculated way that everything that cannot comes to terms within which framework are literally banished, repressed, push away, much like the OP’s brother holding a Masters Degree in Education would not acknowledge perceivable audio differences, when everyone else could hear it. The reason this person would not acknowledge perceivable audio differences is akin to the mistake I made when my conscious reasoning mind is not willing to acknowledge the vague feeling that something is wrong, because logically I could not sensibly discern a reason thereof. In the same way the OP's brother could not hear audio differences with cables because the frequency spectrum should scientifically be all the same.

I don’t know who taught DaVinci about physics, but I asked what makes his Mona Lisa such work of art. One could, of course, says that she has a mysterious smile or that there is something elusive about her, etc., but truth be told our reasoning minds are not able to explain that very thing that makes this painting a masterpiece. That which speak to the heart do so in a language not comprehend by the logical mind. The conscious mind plan, solves problem, etc., the unconscious mind transcend.

IMHO there exists vast difference between intelligent and wise, one of which being the latter acknowledge there is only so much that the mind could comprehend, and requires a healthy dose of humbleness.