Question re Hi-Res Audio

Rupert

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As most adults' normal hearing range is somewhere between 20hz and 20kHz (similar to the frequency range of a good quality CD) what is the appeal of hi-res audio?

If it's for the benefit of those who listen to their music from downloads (MP3, etc.) then fair enough, since the compression will have greatly reduced the quality of the recording, and presumably hi-res audio is attempting to reverse the effect of the compressed signal.

But if you only listen to music from CDs or good qualiy DAB broadcasts, then I'm not sure what the boffins are hoping to achieve. As I see it, they're trying to deliver more information than we're able to hear anyway, so what's the point?
 
manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
+1

The answer is in the name. It's high resolution not higher frequencies.

A bit analogous with a tv picture. Think normal versus 4k, the more pixels the better the picture.
 

manicm

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There's a nice Naim thread discussing Bob Stuart's view:

http://forums.naimaudio.com/topic/what-is-high-resolution-audio

He seems to think a sufficient spec for hires audio is 18bit/96Khz. Apparently Meridian have a white paper on this.
 

The_Lhc

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manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
That statement is completely meaningless, 16-bit 44.1khz will reproduce any analogue signal up to 22.05kHz PERFECTLY.

You can't retrieve more detail than perfect.
 
K

keeper of the quays

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The_Lhc said:
manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
That statement is completely meaningless, 16-bit 44.1khz will reproduce any analogue signal up to 22.05kHz PERFECTLY.

You can't retrieve more detail than perfect.
i had my first taste of high end cd replay last night..it was a cyrus cdxtse and its dac! I had never thought cd could sound so good..made my hi res walkman sound bit 'meh' through hifi.
 

shadders

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The_Lhc said:
manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
That statement is completely meaningless, 16-bit 44.1khz will reproduce any analogue signal up to 22.05kHz PERFECTLY.

You can't retrieve more detail than perfect.
Hi,

I would have to disagree.

Nyquists theory states sampling period is required to be at least 2x the maximum frequency in the signal to be perfectly reconstructed, where the impulse reconstruction waveform will be a sinc pulse. This theory is based on the amplitude of that sinc pulse being EXACTLY the same as the amplitude of the previous analogue signal that was sampled. This is not possible with 16bit ADC which will introduce quantisaton noise - where the value assigned as a sample is the closest possible given the resolution for a 16bit system. The use of 24bits reduces the quantisation error significantly from 16bits. Hence, you can encode at 24bits, to retrieve more information when the signal is reconstructed. Whether you can hear it is another question.

Regards,

Shadders.
 

iMark

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shadders said:
Nyquists theory states sampling period is required to be at least 2x the maximum frequency in the signal to be perfectly reconstructed, where the impulse reconstruction waveform will be a sinc pulse. This theory is based on the amplitude of that sinc pulse being EXACTLY the same as the amplitude of the previous analogue signal that was sampled. This is not possible with 16bit ADC which will introduce quantisaton noise - where the value assigned as a sample is the closest possible given the resolution for a 16bit system. The use of 24bits reduces the quantisation error significantly from 16bits. Hence, you can encode at 24bits, to retrieve more information when the signal is reconstructed. Whether you can hear it is another question.
Sorry to be a bit pedantic, but you probably mean Nyquist's theorem rather than theory.

"A theorem is a result that can be proven to be true from a set of axioms. The term is used especially in mathematics where the axioms are those of mathematical logic and the systems in question.

A theory is a set of ideas used to explain why something is true, or a set of rules on which a subject is based on."
 

shadders

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iMark said:
shadders said:
Nyquists theory states sampling period is required to be at least 2x the maximum frequency in the signal to be perfectly reconstructed, where the impulse reconstruction waveform will be a sinc pulse. This theory is based on the amplitude of that sinc pulse being EXACTLY the same as the amplitude of the previous analogue signal that was sampled. This is not possible with 16bit ADC which will introduce quantisaton noise - where the value assigned as a sample is the closest possible given the resolution for a 16bit system. The use of 24bits reduces the quantisation error significantly from 16bits. Hence, you can encode at 24bits, to retrieve more information when the signal is reconstructed. Whether you can hear it is another question.
Sorry to be a bit pedantic, but you probably mean Nyquist's theorem rather than theory.

"A theorem is a result that can be proven to be true from a set of axioms. The term is used especially in mathematics where the axioms are those of mathematical logic and the systems in question.

A theory is a set of ideas used to explain why something is true, or a set of rules on which a subject is based on."
Hi, Thank you. That made all the difference. Regards, Shadders.
 

shadders

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basshound said:
Or it could be a ruse from the record companies to get you to buy the same music all over again..............
Hi,

Possibly, but the industry added dither to the LSB of a 16bit recording to nullify the quantisation error effect that could be heard. Dither spread the error across the audio band (simply stated), so it was less audible. If we can hear effects on the LSB then we can probably (your experience may differ) hear the differences due to a 24bit recording.

Regards,

Shadders.
 

manicm

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basshound said:
Or it could be a ruse from the record companies to get you to buy the same music all over again..............
Hires has never been required for the recycling business, quaint 16/44 has proved to be quite lucrative thank you.

God bless Phil Collins.
 

MajorFubar

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Anyone who feels anything higher than 16/44 makes one iota of difference to the sound is more than welcome to try their own re-sampling of their favourite hi-res album and report back if they can geuinely hear the difference in a controlled test. No excuses, anyone with a computer can do it, the only software you need in order to try the experiment for yourself is free. But the people who won't are the ones who don't want to prove themselves wrong, and commonly come out with such lame excuses as "I don't have the technical skills to know how to do that, and why should I have".
 

paulkebab

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I'm genuinely happy you've heard how good digital can sound, I for one will never go back to an analogue source...everyone to their own though. On topic, I won't be sucked in with this hires thing. It probably does sound different but is that better? Hear how different CD's sound depending on who and how it was engineered; we strive for equipment with a flat EQ then some idiot in the studio makes a right arse of it all. The pixel analogy is worthless but worth commenting on for another reason. 8K screens are already out and working so why not release them? Coz there's a lot of money to be made in 4K technology so they'll milk that first...same stance with hires audio.
 
K

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paulkebab said:
I'm genuinely happy you've heard how good digital can sound, I for one will never go back to an analogue source...everyone to their own though. On topic, I won't be sucked in with this hires thing. It probably does sound different but is that better? Hear how different CD's sound depending on who and how it was engineered; we strive for equipment with a flat EQ then some idiot in the studio makes a right arse of it all. The pixel analogy is worthless but worth commenting on for another reason. 8K screens are already out and working so why not release them? Coz there's a lot of money to be made in 4K technology so they'll milk that first...same stance with hires audio.
think theres something in what your saying! I have wondered what the ceiling height of cd playback is? Like a record cds are perfect? In as much as its the retrieval equipment that is lacking re resolution..i happen to think one needs to spend a lot more on vinyl retrieval kit..this cyrus and its dac were £900 secondhand..so the cost of high quality cd machines/dac/transport is coming down..i put hi res downloaded from linn and hd music from you tube (thru dac) to my kit..i have some sacd i play too..these cyrus machines are a marvel!!! Why would anyone have a different format? Im talking hifi sit and listen..not portable..cds are cheap as chips..bad recordings aside..they are stellar! You need nice kit to hear how good it can be..its cheaper now secondhand...everyone wants streamers..hard drives etc..i have seen many posts where people have got rid of their cds!!!! Like with vinyl...thankyou! Im buying them..if it wasnt for all these hi res..wav, flac etc..these cyrus machines will be very pricey secondhand..thanks...im going cd...when i have some money ill be getting a cyrus cdxtse and its dac...its a no brainer! (funny thing is i used to moan bout cds..small..cant read sleeve notes..dont feel as tangible as records..lol..cyrus has changed my view..
 

andyjm

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Rupert said:
As most adults' normal hearing range is somewhere between 20hz and 20kHz.
No one posting on this site will have hearing up to 20KHz. Google 'hearing response as a function of age'. If there is anyone sub 20 years old who hasn't attended too many concerts posting, then 17KHz might be achievable - depending on how loud he has had his iPhone over the last few years.
 

andyjm

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Al ears said:
manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
+1

The answer is in the name. It's high resolution not higher frequencies.

A bit analogous with a tv picture. Think normal versus 4k, the more pixels the better the picture.
The reason 4K appears better is that current technology hasn't yet reached the full resolution of your vision. Improving the resolution of the picture above 1080p is noticable.

Redbook CD standard (16/44.1) was deliberately chosen to be better than human hearing. Higher dynamic range, and higher frequency than humans can perceive. Improving it so that it is further above your ability to perceive it - is just wasted bits.
 

manicm

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I don't care if we can't hear above 20khz, CD wasn't a perfect medium, I mean at the 11th hour Herbert Von Karajan had to convince them to extend playback time to 74 minutes. They probably should have made it 24/96 from the outset too.
 

andyjm

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manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
Well yes, and no. With digital sampling, dynamic range, resolution and signal to noise ratio are all in the same bed and are different ways of looking at the same effect.

16 bits will give you 96dB of range, from the loudest sound recordable on a CD to the quietest. You can't hear that range of sound in the real world. So as it is, 2 or 3 bits of the 16 bits of resolution are wasted because the detail is below the perceivable noise floor. Increasing the number of bits does mean more detail, but as you still can't hear it, why bother?

The highly praised 'analogue' BBC stereo FM transmissions were in fact digital 13 bit linear PCM with a cuttof frequency of 15KHz.
 

andyjm

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manicm said:
I don't care if we can't hear above 20khz, CD wasn't a perfect medium, I mean at the 11th hour Herbert Von Karajan had to convince them to extend playback time to 74 minutes. They probably should have made it 24/96 from the outset too.
It wasn't perfect, but it was damn good. I think if the engineers could do it all again with modern technology, they would have had a higher sampling frequency, just because it made some of the downstream analogue filter design easier. I dont think that they would have increased the bit depth. Absent classical music which does make use of a CD's capability, modern compressed music could probably get away with 8 or 10 bits and still have headroom to spare.
 

TrevC

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manicm said:
I don't care if we can't hear above 20khz, CD wasn't a perfect medium, I mean at the 11th hour Herbert Von Karajan had to convince them to extend playback time to 74 minutes. They probably should have made it 24/96 from the outset too.
Erm, it's 80 minutes playing time and already far better than human ears as it is.
 

steve_1979

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andyjm said:
manicm said:
I don't care if we can't hear above 20khz, CD wasn't a perfect medium, I mean at the 11th hour Herbert Von Karajan had to convince them to extend playback time to 74 minutes. They probably should have made it 24/96 from the outset too.
It wasn't perfect, but it was damn good. I think if the engineers could do it all again with modern technology, they would have had a higher sampling frequency, just because it made some of the downstream analogue filter design easier. I dont think that they would have increased the bit depth. Absent classical music which does make use of a CD's capability, modern compressed music could probably get away with 8 or 10 bits and still have headroom to spare.
I think that the computer standard 16/48 is the ideal format for modern digital music. It doesn't sound better than CD quality 16/44.1 but the mathematics involved are simplified when using 16/48 which makes things a little easier at a software level for the computer and software designers.
 

shadders

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andyjm said:
Al ears said:
manicm said:
While you may not hear the higher frequencies, higher bit rates should yield greater detail retrieval from recordings.
+1

The answer is in the name. It's high resolution not higher frequencies.

A bit analogous with a tv picture. Think normal versus 4k, the more pixels the better the picture.
The reason 4K appears better is that current technology hasn't yet reached the full resolution of your vision. Improving the resolution of the picture above 1080p is noticable.

Redbook CD standard (16/44.1) was deliberately chosen to be better than human hearing. Higher dynamic range, and higher frequency than humans can perceive. Improving it so that it is further above your ability to perceive it - is just wasted bits.
Hi,

I would disagree. As I have posted previously, dither was added since the LSB created audible artefacts if the LSB energy was not spread within the audio band. As an analogy, the Musical Fidelity mono block has an extended frequency to 100kHz, and they state that the extended frequency has an effect which is audible. So we could either limit all amplifiers to 22kHz and there would be no impact as we cannot hear it, or try and exceed our current capabilities and see what happens. Some good may come of it. As for digital, we should always stretch the boundaries, since in the limit, a digital recording with a high sample rate and high resolution will tend towards the original analogue recording, which is what we are all pursuing.

Regards,

Shadders.
 

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