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Old 25th August 2012, 10:25 AM   #26951
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Quote:
Originally Posted by RNMarsh View Post
And, i can hear no random noise but distorted music at low recorded levels in digital. No mystery to that.
Then you have (for whatever reason) a bad implementation. This has nothing to do with number of bits, which ONLY sets noise floor. That's been discussed to death here, and there's plenty of links to demonstrations of this (most notably at Werner Ogiers's site).
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Old 25th August 2012, 11:50 AM   #26952
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Originally Posted by Chris Hornbeck View Post
A good seat in an unamplified orchestral setting gives peaks of 105 dB SPL, and this should be reproduced cleanly for "realism". 16 bits down is 10 dB SPL, and most folks have to hold their breath to get that quiet. (People are noisy machines in this context.) For typical peak-to-average ratios this (105 dB SPL peak) is an averaged flat 85 dB SPL, mastering level and, to me, very loud.

So for most adults, 16 bits is a comfortable margin.

Thanks,
Chris
Unfortunately you are comparing apples and bananas. When you are talking 105 db. peak levels that is read on a standardized sound level meter. If you wanted to accurately record this you would want at least 10 db. of headroom.

Now when you talk about noise level that is a broadband measurement. As the ear can has the ability to analyze sound in critical bands, there is the ability to pick out signals 30 db. below the broadband noise level.

In speech systems it is considered acceptable when the signal to noise ratio is ZERO db.
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Old 25th August 2012, 12:02 PM   #26953
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Ed, you're comparing apples to pencil sharpeners. We're not talking about recording, we're talking about a playback medium, where the peaks can absolutely go right up to zero dB with no penalty (in fact, that's good mastering practice). That drops the noise floor 90+ dB, quieter than Randy's room or the concert hall, or the studio, or the mike preamps.

This has also been discussed to death in this very thread.
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Old 25th August 2012, 01:26 PM   #26954
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Originally Posted by SY View Post
Ed, you're comparing apples to pencil sharpeners. We're not talking about recording, we're talking about a playback medium, where the peaks can absolutely go right up to zero dB with no penalty (in fact, that's good mastering practice). That drops the noise floor 90+ dB, quieter than Randy's room or the concert hall, or the studio, or the mike preamps.

This has also been discussed to death in this very thread.
Yes SY,

This is old stuff. When the standards were set for digital audio the idea was that it would be as good as or better than the existing analog methods.

In a typical listening space the noise level will be NC35 or better. Although some argue that when you play back a recording at a lower level, due to Fletcher-Munson type of issues, you change the timbre.

But even with music peaks reproduced to read 85db. the player must reproduce the equivalent of 95db.

The noise level usually is mostly low frequency energy which is why the NC ratings count it less. But there still is a drop in mid and high frequency energy. So tones as low as -5db. may still be heard.

The result is that a true 16 bit recording should be fine for a typical room on much material, but it is not able to cover the entire range of human hearing.

P.S. I prefer a sharp pencil!

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Old 25th August 2012, 01:50 PM   #26955
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As long as the other noise sources dominate, the noise floor of the playback medium is not terribly important. And we're not talking about the range of human hearing (which are group maxima, not the same person), we're talking about the noise floors of studios, concert halls, playback rooms, and mike preamps, which dominate competent recording practice. And these noises are uncorrelated with the playback medium noise floor, so they sum as powers, increasing the influence of the dominant source.

So we're back to meter reading and test signals as opposed to playback of musical program. Maybe that's where we are differing, our definition of the goal of a playback medium.
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Old 25th August 2012, 02:33 PM   #26956
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..... where the peaks can absolutely go right up to zero dB with no penalty (in fact, that's good mastering practice).......
No, it is not! Good mastering practice is to leave a couple of tenths of dB headroom. When using oversampling low pass filters on playback, under certain circumstances, inter-sample peaks might be higher than 0dBFS.

http://www.tcelectronic.com/media/le...per_aes109.pdf

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Old 25th August 2012, 02:46 PM   #26957
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I would like to make a point about various people's opinions as to what is 'good enough' for highest quality audio reproduction.
Back when many here were just teenagers (1968) I used to debate the same thing at the Ampex Audio Department.
You see, my colleagues (and my boss) could NOT understand why I wanted to continually improve the product. For example, the performance spec for 15ips audio bandwidth might be up to 15KHz, no more. They would let the last 10KHz flap in the wind, one way or another. Hi fi standards at the time went from 20-20K, so even DYNA was more careful than Ampex.
One of my assignments was to look at various reproduce heads for their internal quality, or Q. I found out a number of things that showed that we were WAY back in development and were both adding several dB of UNNECESSARY NOISE at every playback of a tape, as well as making the frequency response almost impossible to compensate for. When I commented on this, I got all kinds of chaff: Don't rock the boat, it's to expensive to change, etc, etc. Same as here, sometimes.
Well, that was 1968, I gave my report on head noise, etc and left the Ampex Audio Department for Research. 5 years later, they were BRAGGING about the improvements in their head designs, exactly as I recommended. You see, the pushy, wild eyed dreamer, might, just might, be able to give a company a commercial 'edge' if only they are taken seriously at the time. Their suggestions at improvements will certainly come sooner or later, perhaps from a competing manufacturer.
Another story almost 15 years later:
Dave Wilson and I knew a guy, then, who worked at HP, and was very interested in audio. This guy bought one of the Sony F1 based digital recording systems based on video tape. This guy was elated! He was satisfied! He said the digital recording and playback was PERFECT! And he insisted he was right, to everyone else.
The rest of us we trying these things out and then trying to make them better.
Well, as time went on, there was some announcement from SONY that they had IMPROVED the digital recording process. At this point, Dave Wilson teased the HP guy about digital already being 'perfect', so how could they improve it?. His response was: 'Better than perfect' I don't know if this guy still likes audio in the same way today, but he found HIS answer back before CD was even available. The rest of us tried to make the F1 sound better through modification. People sent them to me for modding, and I did the best that I could with them. Where are they today?

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Old 25th August 2012, 03:08 PM   #26958
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Originally Posted by elektroj View Post
No, it is not! Good mastering practice is to leave a couple of tenths of dB headroom. When using oversampling low pass filters on playback, under certain circumstances, inter-sample peaks might be higher than 0dBFS.

http://www.tcelectronic.com/media/le...per_aes109.pdf
That's an excellent point. Shave 0.2dB off my numbers.
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Old 25th August 2012, 03:15 PM   #26959
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SY,

The noisiest thing in my house is the clock.

Now my experience is that for symphonic music 20db of headroom is good, but 30db is better. So 16 bits would be the limiting factor.

We both agree for a competent recording under most circumstances 16 bits will work.

However in practice, safety margins are a good idea. As the technology allows it 24/192 can under the right conditions be better. Even though there are no true converters for that level!

Now there is a reason why so many old records sound so good. Who keeps and shouts about old bad records?

By the same measure there are a lot of bad CDs. The first generation were only 9 bit linear.

This is all old stuff. But I do object to you including mic preamps in the 16 bit limit. They are way better than that.

One of the projects I may get to is a mic preamp that is quiet, has headroom and AES output. I need this for the dynamic range of sports announcers.
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Old 25th August 2012, 03:47 PM   #26960
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OK, my mike (nothing exotic) has a sensitivity of 2.6mV/Pa. Got a mike preamp that will get me better than -90dB noise wrt 1 Pa?
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