Wow, even the 320kbps mp3 looks worse when compared to AAC 256kbps. You can clearly see it gets cut off above 20kHz freq as you mentioned.
Yes but very few humans can hear a 20KHz tone.
There is an argument that the sound might even be better if the highest frequency is cut lower. We are talking about COMPRESSED audio. Given that the bit rate is fixed what you have is a zero-sum game. In other words, if you put one thing in the file then something else has to be removed because the table number of bits is fixed.
So in order to put in a few KHz of bandwidth what did they remove? Did they remove a dynamic range in the bass? We don't know.
So the logic goes that it is reasonable to remove something you can't possibly hear if it allows room to add more of what you can hear. And we can be sure you are NOT able to hear above 20KHz.
All that said the AAC generally sounds better because they use better compression and can fit more in.
Also if you are listening using the built-in speakers and Bluetooth and so on it hardly matters. You'd need some high-end equipment, to notice But "high end" need not cost a lot. Using just a pair of $125 AKG K240 headphones plugged into a MacBook Pro is reasonably high end and if you add a good quality external audio interface you have "studio quality."
Pro-audio gear is generally less expensive than high-end consumer gear -- consumers are gullible, professional engineers aren't. So if you want to take advantage of higher quality audio files, it wil not cost of an arm and a legto buy pro level gear
Again, I just wanted to make the point that higher upper bandwidth might even make a compressed recording soubd worse. With compression is always a trade off, what to keep and what to toss out. The compression software tries to keep the part of the sound we notice the most and chuck-out what we will not miss.
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The difference is really big. The audio quality of 128kbps MP3s is horrible by todays standards - I can't believe we could stand listening to it, even non-audiophiles.
People no longer care about audio quality. What they care most about now is the physical size of the equipment and there is a trend to worse and worse audio gear.
Go back to the 1950's and look at was considered "good", not "over the top" just "good" and it will completely blow away a cell phone. In those days popular music was still jazz and the recording might be a piano, string bass, sax, horns or some other acoustic instrument and the goal of the music playback was to make it soud as if the musicians were actually in the living room. In the 50's all the parts were separate. the most important part was a speaker and they were typically 3 feet tall at least and floor standing. The speaker would be powered by a vacuum tube amplifier and they'd be playing vinyl. What made it sound real was the very low "loading" of the speakers. The physical size vs the power was large.
Over the years the power goes up and the size goes down and today there is no way on earth that a person listening to an iPhone would be fooled for a second that the musicians were actually in the living room.
But of course, you can still buy some very nice stereo equipment if you know how to shop and set it up. Today's high-end is actually better than it was in 1960 but not by much.
So don't say "my today's standards" to mean something good. Standards have been in a decline for at least the last 50 years. We are trading quality for convinance and price.
