This is my blu ray copy of the 1988 anime masterpiece, Akira. I love Akira, and I think
it’s one of the most stunning achievements in animation ever. But I also think, besides
my feelings about Akira, this blu ray itself is very special. Because on this dual layer,
50gb Blu Ray disc, almost half the capacity is consumed by audio data. And this blu ray
also came with a little booklet that explains WHY half this disc is audio. And when I bought
this blu ray many many years ago, this booklet started a little obsession for me.
Because, as it turns out, the composer for Akira’s score, Tsutomu Ooohashi, is also
a brain scientist. And since his work on Akira, he and his team of scientists have been researching
something called the Hypersonic Effect.
Now the limit of human hearing is generally considered to be somewhere around 20 to 22kHz.
Over the years what Oohashi’s team of researchers have done is conducted a series of experiments
where they played music for listeners, and sometimes the music was a version that contained
very very high frequency sound, very very high frequency information above 22kHz, and
sometimes they would play versions that didn't contain this high frequency sound. And what
they found was, listeners exhibited more brain activity on EEG scans and expressed a pleasurable
perception of higher audio quality when they were exposed to this high resolution music.
Now Oohashi called these changes the Hypersonic Effect. And here's a 2000, here's a paper
from 2000. "Inaudible High Frequency Sounds Affect Brain Acitivty: Hypersonic Effect".
And because Oohashi wanted everyone to experience the Hypersonic Effect, he had a custom mixing
console built, and he painstakingly oversaw a new mix for the Akira blu ray to make sure
that all this high frequency information from the original analogue tapes was preserved.
And that is why the Akira Blu Ray has 5.1 channels of 192kHz audio at a 24 bit bit depth,
so that high frequency information up to 96kHz can be reproduced from this disk. And in this
little booklet that comes with the disc Oohashi recommends that the viewer construct a viewing
environment with the right equipment that can reproduce all this high frequency information
that this disc is bursting with. And maybe its sort of like the placebo effect but it
even feels like this disc is heavier than your normal blu ray.
When I got this Blu Ray, it put me into a flurry of trying out all the different output
sampling rates on my new PS3, and watching the movie at tremendously high volumes, hoping
my head would just kind of explode with pleasure from all the high frequency information. And
if you have watched Akira, you KNOW that it is the kind of movie with the kind of score
that could make your head explode.
Since those younger, more naive times, I’ve learnt a lot. I’ve learnt that, for instance,
the results that Oohashi found in his original 1991 studies could NOT be replicated in follow
up studies by the NHK Laboratories. I’ve learnt that many many studies have been conducted,
trying to see if listeners can in some way feel or perceive high frequency audio, and
the results have been very mixed. And since Akira’s return to the earth, the audio market
has also learnt something: the market has learnt that if you put a “High Resolution”
sticker on gear people will pay more for it, even if there has been poor evidence that
this sticker isn’t bullshit.
For me personally, I came to the conclusion, after doing my own volume matched listening
and my own blind tests, that in a normal listening environment most people can’t tell lossless
from lossy compressed audio apart, let alone higher sampling rates or bit depths. And you
can watch some of my many previous videos on the subject, where I talk about lossless
versus lossy audio, I talk about the importance of double blind testing, I talk about 24 bit
audio. Honestly, and I know some of you agree with me on this, those videos I think have
been some of the most important and helpful videos I’ve made for this channel.
Because to me, this question of high resolution audio and this sticker has always struck me
as a sort of, marketing departments pushing something of dubious benefit to increase product
sales, like say, 3D movies, or Valentines Day.
Which brings us to the present day, 2016, where through Tyll over at Innerfidelity I’ve
learnt of an important new AES paper from Joshua D. Reiss of Queen Mary University of
London.
And this paper is important because it’s not a just s new study - it’s a meta-analysis
of 17 studies of high frequency audio conducted since 1980, including Oohashi’s original
1991 study.
Now a meta analysis is when you go through previous studies about a subject, you investigate
them for possible issues or issues with experimental design, and then you gather all the results
together to produce a new weighted average which tries to take into account these experimental
errors.
I’ve read this paper, and while I can’t comment on the quality of the paper, or the
quality of the analysis, because I’m simply not trained in data science, I do know that
this kind of work is difficult and it's important, and this kind of work is sometimes undervalued
because it’s much more exciting to be running experiments than it is doing follow up studies
and statistical analysis of these experiments.
The paper is open access and anyone can read it, and I do recommend doing that. I put a
link in the description of this video. Because you can learn all kinds of things about how
high resolution studies have been conducted up until now. But I’ll give you the basic
breakdown of the results.
As I understand it, the take away from this meta analysis is that in all these studies
untrained listeners could identify correctly high resolution material 51% of the time on
average, which is barely better than a coin flip.
Now across studies where listeners were given some kind of training about what to listen
for in high frequency material, trained listeners gave correct answers 62% of the time on average.
The number of results from studies with training was much, much smaller than those that had
untrained results. So overall, trained and untrained listeners together gave correct
answers 52% of the time on average.
Now what this meta analysis suggests is that in experimental listening conditions, with
training, people do seem to be able to be able to identify high frequency material with
accuracy slightly higher than chance. And by slightly higher than chance I mean 62%
of the time.
Now if I told you: LADIES AND GENTLEMEN, I HAVE THIS AMAZING PSYCHIC ABILITY. I CAN PREDICT
THE FUTURE! I am going to flip this coin 10 times, and 6 times out of 10, I can accurately
predict if it will be heads or tails. NOW PLEASE! I REQUIRE TOTAL, ABSOLUTE SILENCE!
Let's go! I predict heads!
Fuck.
I think you would agree that 62% in optimal conditions is not very impressive. It’s
not enough to convince me to fork out more money for high resolution hardware, especially
not in portable listening environments with a lot of background noise. It's not enough
to convince me that people who report hearing a huge difference between high resolution
material and standard resolution material, they aren’t just listening to different
masters or they aren't just being over-enthusiastic.
But at the same time, 62% of the time it does work 100% of the time. So based on this evidence
you can’t outright reject the idea that high resolution audio may have some kind of
effect on listeners. Now this is an interesting result to me, and I wonder about what KIND
of training you could do to increase your accuracy in a double blind test with high
resolution audio. Now the paper also notes that it seems like, this hypersonic effect,
if it exists, seems to last for tens of seconds AFTER hearing a high frequency sample. And
this residual effect is something Oohashi noted in his results. So you may get a more
accurate discrimination result if you listen to longer samples and leave a longer gap - 30
seconds or more - between samples.
You can expect to hear more about this from me in the future, and I’m going to be doing
some more listening and some more reading.
Here are some other interesting things rom this paper. The authors state that a possible
source of bias in these results may be publication bias: ie, small studies that do not find a
difference between high resolution audio and standard resolution audio may not be published.
This meta analysis is important, but it's not the be all and end all, and the authors
recommend that future studies in high resolution audio be done with changes in experimental
design to reduce bias.
Now here's the final caveat. None of the studies in this 2016 meta analysis looked at whether
the effects of high resolution audio could be reproduced with headphones. And Oohashi
himself claims that the hypersonic effect requires that the entire body to be exposed
to high frequency sound through speakers rather than headphones, suggesting that the mechanism
for action for the hypersonic effect, if it does exist, it's actually due to bone conduction
or something else mysterious. For now, the effects that we have studied, if any, come
from using speakers with high frequency super tweeters.
So what are you thoughts? Does 62% sound good to you? Has your faith been shaken? Or are
you gonna go out and buy a bunch of diamond dome tweeters? Now I’ve put links in the
description of this video to some of the papers I've mentioned and I’d love to hear your
comments. If you enjoyed this video, then why not subscribe and watch my previous videos
about sound science?
Now I’ll see you next week, and as always, happy listening!