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Hi fidelity SSB bandwith

Discussion in 'Ham Radio Discussions' started by K1VSK, Feb 27, 2007.

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  1. WD0CT

    WD0CT Ham Member QRZ Page

    After I posted the tv presets I thought about them again.
    The theater setting of 90 and 90 does give a reasonable impression [considering the two little built in speakers] of the big audio I hear at a movie theater.

    I don't get HBO but I can sometimes see the pic and hear the audio somewhat. The signal to noise is way worse than 12db though.

    It is perfect for playing with the bass and treble controls for max intelligibility. I end up around 60 and 70 every time. Strictly high boost does not work for me.
     
  2. N3JI

    N3JI Ham Member QRZ Page

    EDIT: This was in reference to Tim's posts about the NPR clip, not the latest "Koppel" posts. I didn't refresh before replying...

    Definite difference in the 500 HP & 300 HP clips, and most of the high freq stuff was chopped with the 3k LP, so nothing earth shattering there.  I did find the full-range clip annoying, though I didn't pay particular attention to any lost sibilants due to noise.  That's why I chop as low as I can without killing the highs.

    And here I thought you were kidding about the hearing aide comment a few posts ago!  Try listening to my eSSB clip with your HAs in and see if you notice any difference in the lows.  There are plenty there, so I'm wondering if your ears or perhaps the HAs are chopping the lows.

    Joe, N3JI
     
  3. WA0LYK

    WA0LYK Ham Member QRZ Page

    I agree, the last clip (300-4000) sounds the best. The 500-4000 Hz is just missing too much. The 200-2800 would be my second choice.

    Looking at the frequency response of the clip with xmms, it looks like the preemphasis makes the response flat, i.e. the highs show as much loudness as the lows. It sure lets you pick out some of the sounds that the first clip smears. My hearing isn't the best, and maybe this is just making up for that. It may even be making up for poor response of my little Sony speakers. In any case, the intelligibility is better when the highs are boosted.
     
  4. N3JI

    N3JI Ham Member QRZ Page

    Now, about the Koppel clip...

    I found cutting at 200 removed a significant amount of his "personality". But clearly, the 200-4.5k is the most intelligible.

    Joe
     
  5. K3VR

    K3VR Ham Member QRZ Page

    The upper register pre-emphasis seems to help intelligibility by raising the energy level of certain consonants. It's not pleasant listening but it helps. The extended bandwidth in the upper register always helps intelligibility. I don't lose any intelligibility with the lows chopped but I do lose the intention and emotional tone of the speaker.

    It's interesting how much subtlety of intonation and personality is in the lower portion of the male register. I've been listening to the way actors portray emotion in books on tape. Anger, for instance, usually comes across as a low growl; fear is portrayed in the higher registers; shock is often whispered. These guys make a living imitating human behavior. It makes me wonder if intonation in language is unconciously paired with a particular frequency for a given emotion or intention.

    .
     
  6. AB0WR

    AB0WR Ham Member QRZ Page

    Mark,

    One quick note, in the future it might work better to put the narrow bandwidth clips first. That makes it easier to spot areas of increased intelligibility since you haven't already been "biased" by the good clips.

    Now, I immediately noticed that the word "inexperienced" was missing the "d" sound on the end in both the first and the last clip, at least for me. I need to wait a while before listening again so I can get the repeating loop out of my head so I can listen for other "missing" parts.

    It would be extremely interesting to see the difference between clip two and three if the SNR for clip three went clear down to 14db. I'm pretty sure if you took clip 4 down to 14db there would be several areas that I would have a hard time with. My guess is that clip 3 at 14db will have lower intelligibility than clip 2, how much less I don't know.

    tim ab0wr
     
  7. N5RFX

    N5RFX Ham Member QRZ Page

    Here it is:

    The first part is a 60 second sample of the original file with 6 dB per octave pre-emphasis and 200 - 4500 Hz filtering. The SNR is 14 dB

    The second part is A 60 second sample of the original file with 6 dB per octave pre-emphasis. The SNR is 14 dB
    Tim's Request
    73,
    Mark N5RFX
     
  8. N5RFX

    N5RFX Ham Member QRZ Page

    When pre-emphasis is added to the original 60 second sample, the PEP to average ratio goes up by 6 dB.

    No pre-emphasis 15 dB
    Pre-emphasis 21 dB

    This ratio holds throughout the bandpass filtering.

    73,

    Mark N5RFX
     
  9. WA0LYK

    WA0LYK Ham Member QRZ Page

    Some comments.

    I had no problem understanding everything said even at this noise level. The noise is starting to become distracting but I think preemphasis would help at an even higher level of noise.

    The preemphasis on the unfiltered clip made the s's sound overemphasized, almost like a snake. Might have to live with this to get the other benefits. There would be no doubts as to what words were plural ('s' on the end). I didn't notice this at all on the filtered clip.

    The 'b' sound in the word 'bloated' was much more pronounced in the unfiltered clip. I don't know if going down to 100 Hz would help a lot with the AI since it was still pretty easy to understand what was being said. However, 'easy' listening would be enhanced with a few more low freqs.

    Some thoughts.

    It would be nice to hear what some folks think that have both good hearing and a good receive audio setup on their rigs. Is the preemphasis 'over the top' for these folks? I know it must be making up some for my hearing loss and for not poor but not the best speakers on my pc. In other words, does it give the same benefit in articulation for these folks as for me? Is it destructive or beneficial for everyone?

    It's funny how were talking about a bandwidth of what traditionally has been a good signal on AM. Did the first hams arrive at this bandwidth because it gave the most understandable signal through experimentation or because the equipment they had, i.e. microphones and audio amps just naturally fell into this range?

    Jim
    WA0LYK
     
  10. N5RFX

    N5RFX Ham Member QRZ Page

    Jim,

    One thing we have not been considering is de-emphasis on the receive end. Here is a clip with 3 samples.

    1st part: A 60 second sample of the original file with 200 to 4500Hz bandpass filtering. The SNR is 12 dB

    2nd part: A 60 second sample of the original file with 6dB per octave pre-emphasis and 200 to 4500Hz bandpass filtering. The SNR is 14 dB

    3rd part: The second part with 6 dB per octave de-emphasis. The SNR is 19 dB
    pre-emphasis_de-emphasis
    73,
    Mark N5RFX
     
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