Dr. AIX's POSTS — 01 October 2014

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An Audiophile Midterm

As I sit on Southwest Flight 2708 from Los Angeles to Chicago on my way to the New York Audio Show (the second leg of the flight flies to La Guardia), I thought it might be interesting to pose a series of questions that will let you know how much you know about the subject of high-resolution audio. After all it is midterm time at the university.

Below I present 10 questions. Answer them as best you can and tomorrow, I’ll provide the answers and briefly discuss the items. Let’s see how much you know about HRA.

1. What is the nominal dynamic range of a standard 2-channel stereo analog tape master?
A. 96 dB
B. 60 dB
C. 45 dB
D. Infinite
E. None of the above

2. Which of the following listed formats qualify as HRA?
A. Vinyl LP
B. Analog Tape
C. 44.1 kHz/16-bit PCM
D. DSD 64
E. None of the above

3. True or False: Any analog recording that has been transferred to a 192 kHz/24-bit PCM digital file is considered high-resolution audio.

4. How many digital bits are required to capture the dynamic range of a typical pop/rock CD release?
A. 1-bit
B. 8-bits
C. 24-bits
D. 4-bits
E. 16-bits

5. Which items below are true with regards to Dolby Digital (AC-3) encoding?
A. It throws away some of the audio data in the uncompressed track
B. Limited to 5.1 surround sound encoding
C. Uses data rates from 192 to 1500 kbps
D. Originated as Meridian Lossless Packing and became Dolby TrueHD
E. All of the above

6. Spreading audiophile “gels” or other “enhancement” liquids on optical discs can
A. Increase low level details and resolution of the music
B. Tighten up bass instruments resulting in more low-end definition
C. Improve the rhythmic pacing of recorded music
D. Minimize digital errors passed to the optical pickup
E. All of the above

7. True or False: Analog recordings have “infinite” resolution and are therefore more accurate than digital recordings, which use small stair steps to encode audio.

8. True or False: Increasing the number of bits in your digital samples increases the resolution of a recording.

9. Dither is a digital process that?
A. Adds noise thus reducing the dynamic range of a PCM recording
B. Randomizes the least significant bits of a PCM digital word
C. Reduced the dynamic range of a Redbook CD from 96 dB to 93 dB
D. Required to ensure that digitization errors are equally spread
throughout the frequency spectrum
E. All of the above

10. True or False: A DSD 64 recording with a sampling rate of 2.8224 MHz has 64 times the fidelity of a standard CD with a sampling rate of 44.1 kHz.

So there you have it. The first Real HD-Audio Midterm…ten simple questions that shouldn’t be too difficult to answer…especially if you’ve been reading my posts for any length of time.

Check back tomorrow and we’ll discuss the answers.

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About Author

Dr. AIX

Mark Waldrep, aka Dr. AIX, has been producing and engineering music for over 40 years. He learned electronics as a teenager from his HAM radio father while learning to play the guitar. Mark received the first doctorate in music composition from UCLA in 1986 for a "binaural" electronic music composition. Other advanced degrees include an MS in computer science, an MFA/MA in music, BM in music and a BA in art. As an engineer and producer, Mark has worked on projects for the Rolling Stones, 311, Tool, KISS, Blink 182, Blues Traveler, Britney Spears, the San Francisco Symphony, The Dover Quartet, Willie Nelson, Paul Williams, The Allman Brothers, Bad Company and many more. Dr. Waldrep has been an innovator when it comes to multimedia and music. He created the first enhanced CDs in the 90s, the first DVD-Videos released in the U.S., the first web-connected DVD, the first DVD-Audio title, the first music Blu-ray disc and the first 3D Music Album. Additionally, he launched the first High Definition Music Download site in 2007 called iTrax.com. A frequency speaker at audio events, author of numerous articles, Dr. Waldrep is currently writing a book on the production and reproduction of high-end music called, "High-End Audio: A Practical Guide to Production and Playback". The book should be completed in the fall of 2013.

(7) Readers Comments

  1. 1) b (just guessing but analog tape seems to be about 10 bits resolution, maybe a bit higher when conditions are better than “nominal”)
    2) e (format is not (or at least should not be) an indication of HRA by itself)
    3) False (at least by what I think would qualifiy as HRA, although CEA and others seem to think the answer is “True”)
    4) d (a bit of a loaded question, with no idea exactly how “typical” is defined, but plenty of Loudness War victims only need 4 bits (24 dB range) to reproduce the dynamic range of the master)
    5) a (this was tricky: I feel confident “a” is true, “b” is a trick item since it’s limited to 6 channels so it could be 6.0 or 5.1 or something else that adds to 6, “c” upper range seems too high for lossy, and “d” doesn’t seem right since MLP and TrueHD are lossless and thus shouldn’t depend on lossy data compression approaches)
    6) e (I don’t like any of the choices and strongly prefer a “none of the above” choice, but “e” seemed the least offensive to common sense among the choices. But I would expect any liquid on a disc to eventually foul the optical pickup (since optical pickups are typically under a disc) or otherwise create more refraction issues than it solves. If a liquid would be allowed to dry and then polished, then I feel more comfortable with “e”.)
    7) False (LOL. Nyquist-Shannon)
    8) False (as a general rule without further clarification, and under any condition for playback. But if just from a recording perspective and if one’s noise floor of the entire recording, mixing and mastering chain is lower than one’s current recording bit depth, then “true”)
    9) b (I LOVE this question. Not even tricky, just very insightful)
    10) False (can’t compare the 1 or 4 bit PCM-like sampling and noise shaping dither of DSD with conventional PCM 16 bit sampling on a 1:1 basis for sampling rate. In most cases, fidelity will probably be limited by recording and processing chain noise rather than the exact digital sampling method).

    Regardless of my score, absolutely my favorite blog post of all time for your website.

    • ooops – typo – I meant “d” for question 6. My subsequent pontification should make more sense with “d” as the least worst choice as I intended. Doh!

  2. Off the top of my head, no googling, here are my answers:

    1. What is the nominal dynamic range of a standard 2-channel stereo analog tape master?
    B. 60 dB

    2. Which of the following listed formats qualify as HRA?
    D. DSD 64

    3. True or False: Any analog recording that has been transferred to a 192 kHz/24-bit PCM digital file is considered high-resolution audio.
    A: Not true, except that it probably qualifies as ‘HRA’.

    4. How many digital bits are required to capture the dynamic range of a typical pop/rock CD release?
    B. 8-bits

    5. Which items below are true with regards to Dolby Digital (AC-3) encoding?
    A. It throws away some of the audio data in the uncompressed track
    C. Uses data rates from 192 to 1500 kbps

    6. Spreading audiophile “gels” or other “enhancement” liquids on optical discs can
    D. Minimize digital errors passed to the optical pickup…. SOMETIMES

    7. True or False: Analog recordings have “infinite” resolution and are therefore more accurate than digital recordings, which use small stair steps to encode audio.
    FALSE

    8. True or False: Increasing the number of bits in your digital samples increases the resolution of a recording.
    TRUE

    9. Dither is a digital process that?
    E. All of the above

    10. True or False: A DSD 64 recording with a sampling rate of 2.8224 MHz has 64 times the fidelity of a standard CD with a sampling rate of 44.1 kHz.
    FALSE

    • You know…I’m not sure that Google would get it right.

  3. 1. Nominal dynamic range of analog tape master: B. 60 dB.
    2. Only D. DSD 64 could but generally does not since it is not a source. No one records directly to DSD.
    3. False: A transferred to a 192 kHz/24-bit PCM digital file can come from an 8-track machine. It is generally an up conversion.
    4. C. 24-bits in PCM is required to capture the dynamic range of a typical pop/rock Band. But for the CD mastering, unfortunately only B. 8-bits is used.
    5. AC3 is a video standard that uses MPEG-1, which is stereo, or MPEG-2, which is limited to 448 kbps and can be 5.1 surround.
    6. Spreading audiophile “gels” or other “enhancement” liquids on optical discs cannot achieve any of the suggested choice. So the answer is: F. None of the above.
    7. False: Analog recordings does not have an “infinite” resolution.
    8. False. Increasing the number of bits in your digital samples changes the dynamic range not the resolution of a recording.
    9. E. All of the above
    10. False: “ fidelity” is not even defined.

  4. I’ll have a go at it (no googling).

    1) b – 60dB
    2) d – DSD 64
    3) false – (depends on the source)
    4) 4 bits – (based on your Tom Petty remark but maybe that was hyperbole)
    5) c
    6) This one is a joke, right?
    7) false
    8) false – it only increases dynamic range even then it depends on the source
    9) e
    10) false – apples and oranges.

    Please feel free to apply correct answers to what is surely a less than stellar “real” midterm score 🙂

  5. I’ll try my chance:
    1: B 60dB
    2: E None of the above. [DSD64 is close to the mark as it has considerable dynamic range, but its frequency extension only goes up to 22kHz because of noise shaping, and 22kHz sounds a bit too low for HRA]
    3: False
    4: E 16 bits. I chose this because 8 bits seems too low, even if 16 bits are overkill for ultra-compressed modern pop-rock. I would think that 14 bits are probably enough.
    5: I have no clue and don’t want to google it.
    6: D. I chose this option only because my preferred answer (“none of the above”) was not available.
    7: False
    8: True but inefficient.
    9: E
    10: False (1 bit vs 16 bits)

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