hello everyone this is amir from audio science review this is a first video in what i hope
to be a series of videos uh looking inside high resolution audio from an objective and
measurement point of view and see what's going on in them uh high resolution audio is getting
more popular but there's a premium to purchase the tracks and uh would be nice to know for
getting something extra for the money that we're spending so here i've just picked an example um
music that i've purchased from the audio company name they actually have a high resolution download
service and from one of my favorite artists antonia forcione as you can see in here title
is meet me in london and the download sampling rate is 192 kilohertz um what i'm going to do is
open the first track in adobe edition i've already done that so we don't have to wait for it once we
open that we see three different displays in here first one is an amplitude display so as time goes
by showing us showing us how loud the music is getting we see uh plenty of black in here which
is what i like to see meaning uh they have not tried to push the music all the way to the maximum
um the they're staying below that there's air in there and so that means loudness compression if
used is pretty mild i'm not going to talk about this just yet this is a spectrum splay display
i'm going to get you to look at this side this is a is a Fourier transform
of the time domain music samples what that means is that it's telling us what frequencies exist
inside that music and how loud they are starts from zero hertz
and goes all the way up to half the sampling rate of 192 kilohertz which gives us 96 kilos
so let's go ahead and play a little bit of this music and see what we have
so what we see if i zoom out a little bit uh and then just bring the area of interest in focus
we see the music playing over here and it goes up and down as it should uh but then we see some
other odd things we see a tone in here which is a problematic uh let me stop it right there
uh this uh what i call idle tone or beacon is sitting here at around 45 kilohertz
it has nothing to do with the music is what we call not correlate correlated with the music
and it's just sitting there it's a pure tone a single frequency uh what's the cause of it
most likely it's a scan rate of the monitor that they use monitors start displaying one pixel from
this corner and scan the lines get all the way to the bottom and to jump up depending on the
resolution they put out a pure tone and the analog the digital converter being sensitive
has picked this up it could also be a ultrasonic alarm in the building or any of the other sources
but definitely it's not music what's not music is also this other one over here we
have another one over here and one that's pretty dangerously close to the audible frequency band of
20 kilos so we have one over here at around uh 22 killers or so none of this again is music
should not be there's disappointing now if we look in here this is also a spectrum display
but it's sort of a heat map where colors have been assigned to amount of intensity at that
frequency in it what we want to look at is this steady state horizontal lines if you look in
here we've got one over here one over here these exactly correspond to these peaks that i've been
talking about this is the 45 kilos one and we see it right over here this is a 25 22 kilos more boom
is also sitting here you also see a few other ones that go actually within the audible band
don't want to be too critical of those it's hard to examine what they are
but you know music is sort of random in nature we want to see it to be noise-like like this
we do not want to see correlated pure tones that last the entire track if they are that means
they're just pure frequencies that are not music you wouldn't have whistle playing the whole time
at exact one tone uh low band at low frequencies why have it at high frequencies so this is just
not acceptable uh this is all total garbage it's gonna potentially be amplified by your amplifier
and making it work harder sometimes you can make some amplifiers oscillate and it could also drive
your twitter and cause intermodulation distortions that actually can fall back to the audible band
could have been easily caught the simple analysis as you saw takes no time at all every audio
workstation's offer has such a display and they should have found and eliminated these sources
if they can't eliminate it then they should have used a lower sampling rate to not include them
no reason to have that speaking of sample rate let's look at the spectrum that was used
was the bandwidth used wisely we see this sort of a waterfall drop of our music over here
but then you know we see that it sort of levels off that's not natural it then it goes goes down
and here it goes back up at half the roughly half the sampling rate this is clearly noise
is probably caused by noise shaping in an analog digital converter or something along
the way it is not natural it's not part of the music this is pure nonsense pure garbage
and uh if we play the music we can dynamically see how much of the content is actually correlated
together and that's likely our music spectrum so we see this obviously up to 20 some kilohertz
is definitely music what's over here is somewhat questionable does not change with the content of
music most of the time but if i play enough of it occasionally it sort of jumps up and down
in correlation with the lower frequency like it just did so at best i would say
you know useful spectrum goes to 48 kilos or so which means a 96 kilo sampling would have been
plenty it would have unfortunately still included this garbage but it would have eliminated all this
so what i downloaded half of it was garbage half of it was good i don't remember if name charged
me more for 192 kilos versus 96 kilo sampling clear there was no reason to get anything over 96
and you could actually go well below that even 48 kilohertz and and would have been plenty
so very disappointing paid extra and what i was sold was was uh noise and garbage
now they have another track that i downloaded beside that one let me see if i can find that
uh that one uh is a 48 kilo sampling you also see the inconsistency in naming uh from that is
one of my pet peeves the other one they had put 192 killers in the title but this one does not um
but we can play that and quickly figure it out so i've got that one downloaded also
um here in audition but right away we see a problem in the amplitude domain these samples
in here are definitely clipping or you know right at clipping they've kept them just the hair
uh below disappointing the no reason to max these things out
should have had a little bit more headroom in here i can always turn up the volume
if we play this and get it over here and watch the view meters over here
you know this should have been you know the comfortable range where this is in orange
but look at this it goes right to uh zero db uh we can do look at the aperture statistics
and see if it actually has clip but regardless it's just not good uh we shouldn't have seen that
but uh let's go ahead and play the music um we see that the audition is smart enough that
has stopped the uh at uh what looks to be a 24 kilohertz which tells me it's 48 kilo sampling
this is a live recording and uh almost invariably uh the sampling rate of audio that goes with video
concerts is 48 killers so that makes sense as far as whether it's all good let's play that
we see that all of it jumps up and down correlated which is the message i was trying to convey in the
last one uh so this is all you know up to the end maybe it's pretty good stuff um there's a bit of
garbage in here that i don't like right here so we see another thing at 19 kilohertz that's whaling
you know levels pretty decent minus 100 minus 75 db minus 73 db should not be there uh and
this is smacking in audible band uh but you know due to masking because everything else is loud
it's not hurt or the older person like me that's listening to this that produced this couldn't hear
18.2 or whatever this is 18 yeah 18.2 kilohertz should not be there it's an artifact but the rest
i should say this is actually reference quality recording but you know not doesn't have full
hygiene much better bet than the uh 192 killers at least we're not downloading a bunch of noise and
junk we're downloading real music and uh but then we have clipping in here look at what's
happening here uh it's just not acceptable to have this maxed out it should have been
should have had a little bit of headroom anyway hopefully you found this educational
as i mentioned i'll be producing more of these uh digging into uh you know other tracks that i
have and you know it's like a reality show every one of them is going to be different
thank you for tuning in and uh talk to you later in the future video bye-bye