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Old February 23rd, 2008, 12:49 PM   #1
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the difference between 16/44 and 24/96 can not be heard

From AES Journal 2007 September, Volume 55 Number 9:

"Audibility of a CD-Standard A/D/A Loop Inserted into High-Resolution Audio Playback

E. Brad Meyer and David R. Moran 775

Conventional wisdom asserts that the wider bandwidth and dynamic range of SACD and DVD-A make them of audibly higher quality than the CD format. A carefully controlled double-blind test with many experienced listeners showed no ability to hear any differences between formats. High-resolution audio discs were still judged to be of superior quality because sound engineers have more freedom to make them that way. There is no evidence that perceived quality has anything to do with additional resolution or bandwidth."

Test were done with a high grade stereo system and over one hundred test persons. Nobody could hear the difference between SACD and CD standard audio.
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Old February 23rd, 2008, 02:39 PM   #2
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I bet those same people could tell the difference if they were recording rather than listening to the end product.
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Old February 23rd, 2008, 03:35 PM   #3
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It is far better to record using 24 bits than 16 bits.

One does not need to be as careful in setting the levels to still get quality sound. A low level 24 bit recording may be normalized (the levels may be adjusted) to raise the levels.

While the above mentioned listening test may be true, it should not convince anyone who has the choice or capability of 24 bit recording to use 16 bit recording instead.
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Old February 23rd, 2008, 04:44 PM   #4
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I have a DVD-A player (but not in my music system. It plays DVDs on our TV.) I bought Yes, Close to the Edge in both DVD-A and CD.

The difference is not noticeable for casual listening. However, the soundstage is much better defined with the DVD-A.

I believe that the two were mastered differently. There were some slight differences in reverb between the discs, so it's not 100% apples to apples. And, no, the 24/96 version won't change the 'verb.

I don't believe that the soundstage difference was due to the mastering. The 24/96 soundstage is even bigger *vertically*. The placement of the instruments is more precise and is more stable as the instruments play through their ranges. I'm not talking about differences in spatial processing that put the instruments behind your head.

That said, if I wasn't in the sweet spot while listening intently, I didn't really notice the difference. If you chew every note of your music, 24/96 is worthwhile. If, for you, music is notional, stick with CDs and MP3s.
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Old February 23rd, 2008, 09:59 PM   #5
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I think the failing is their playback system. there are differences. at higher volumes, when 16bit fades down there can be distinct staircase like stepped dropping of the signal. 10 years ago, I could clearly hear the difference between 44.1 and 48K. 44.1 sounded duller. now I might be pushing it a little :(. I don't buy their survey. the entire 44.1 / 16bit is something that was cooked up during the 1960's during the first experiments with digital sound and it was the minimum data rate to emulate "reality". 24 bit has numerous advantages including more dynamic range and lower noise floor.

I'll also add, if those same test subjects ever heard a real 1" 8 track in a studio playing back just recorded tracks, they would much more easily pick out 44.1 16bit, but I'm dating myself.
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Old February 23rd, 2008, 10:20 PM   #6
 
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It really depends on the dynamic range being recorded. If you're recording elevator music, you won't hear any difference. I record a fair amount of high dynamic range rock music. 24 bit has MUCH more dynamic range than 16 bit. It's much more forgiving. AFAIK, this isn't a "philosophical" arguement. The differences aren't open for debate.
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Old February 24th, 2008, 01:42 AM   #7
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In this experiment they only tested if the resolution drop from SACD to CD could be heard, the source was a SACD disk. Nobody could hear it. Obviously not the right people were asked to participate...

24 bits do have more dynamic range, true, but when no recording actually has more than 70 dB of source DR it is a moot point if the media can handle 96 (CD) or about 115 (SACD in real life). In normal listening you will not hear the noise floor anyway, which is way below the listening room noise floor.

This test does not mean 24 bit is useless for recording purposes. 24 bits makes recording easier and safer, but publishing in 24 bit super audio formats is useless.
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Old February 24th, 2008, 03:59 AM   #8
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Quote:
Originally Posted by Petri Kaipiainen View Post
In normal listening you will not hear the noise floor anyway, which is way below the listening room noise floor.

This test does not mean 24 bit is useless for recording purposes. 24 bits makes recording easier and safer, but publishing in 24 bit super audio formats is useless.
Again, I found that 24-bits offers a superior sound stage. This makes sense to me as the additional bits and sample rate can produce much more accurate phase information, which is critical for location cues. This is independent of the noise floor, which I agree is moot.

If you don't listen to music intently while sitting in the sweet spot though, you won't notice the difference.

The "zipper effect" noted previously happens when fading a 16-bit source without enough resolution and with poor dithering when going back to 16-bits. With a good 24-bit+ production and good dithering, you won't hear the zipper effect on a CD.

The worst zipper though is from MIDI's 128 level (7-bit) volume/expression resolution. I'm looking forward to more resolution from Super-MIDI in the next year or two...
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Old February 24th, 2008, 11:24 AM   #9
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It is quite easy to make a test file and try this at home:

- get a true 24/96 recording (I bough one from Linn web shop, FLAC "Studio master" of Prokofiev's 1. symphony)
- convert to AIFF or WAV for processing, keep resolution at 24/96
- Join the traks into one file (4 tracks in this case, total of 14:20)
- cut the file into 30 second clips (28 clips in this case)
- copy clips, convert to 16/44.1 and back to 24/96
- throw dice to deside which resolution clips are used
- join the clips back to form the original perfirmance, some random clips those that were downrezzed 16/44.1, others 24/96 as decided by dice
- listen to the file with a good player capable of true 24/96 performance (I use SD722)
- make you own conclusions.

You can use this with friends by either asking at every 15+n30 seconds it the audio is hi or low resolution, or every n30 seconds if there was a change compared to previous clip.

This method bypasses the need for comparator, level setting etc. If you are really interested in finding out if you can hear the difference this is the way to test it.
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Old February 24th, 2008, 12:42 PM   #10
 
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All I can cite is experience. When recording live music I always use a limiter on the input to my recorder. When I record in 16 bit, I have to run the limiter at a 2-4dB higher than when I record at 24 bit. If I don't, clipping on the peaks is quite noticeable. I always run the recording hot.Dropping the overall level to avoid clipping is too low for the quieter passages....too much S/N there.
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Old February 24th, 2008, 01:42 PM   #11
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Inherently more data pints should allow a higher quality recording with more "information" about the original source, and higher data rates should provide more "room" for that data to knock about...

The problem is that the vast majority of untrained ears will be quite entirely unable ot discern the differences, unless they are trained to LISTEN, and as a practical matter, most listening environments and playback situations will be sufficiently un-ideal as to negate the nuances even for expert ears.

The most important consideration in my mind is to START at the highest possible bitrate, with as much data as possible - you cannot "restore" what is not there, but with the miracles of compression you can take the larger pile of information and condense as needed!
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Old February 24th, 2008, 01:47 PM   #12
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I believe we are all in agreement that there's a huge difference between recording and delivery, with regard to the value of additional bits used for each sample. That was not what the article the OP cited was about. It was ONLY about delivery.

Let's face it: for most people, MP3 defines sound quality these days. Uncompressed CD audio is luxury to most listeners, as are the Dolby Digital and DTS compressed formats. I'm not saying that going any further than that has no value, but it seems to be an appreciable value only to a very small fraction of listeners. That, to me, is the message of this article.

- Martin
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Old February 24th, 2008, 03:14 PM   #13
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You hit the nail on the head, Martin.

Bill, you are right that recording and processing in 24-bits or more is a no brainer. I would run a compressor between the mic and A/D in 16-bits, but in 24-bits there's no need.

The article was about end delivery though, not recording and processing.
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Old February 24th, 2008, 04:46 PM   #14
 
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oh, sorry.
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