greg dahlen

Alumnus, academy of achievement


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what if any is the difference in sound between a recording and a live voice, between a voice on the telephone and the same voice live?

Let's say you heard your mother's voice in the next room. You couldn't see what was in there, and you knew it might be a recording or it might be her in there speaking live. Is there a difference in sound quality between recorded sound and live sound, so that you could know whether it is a recording or her live? If there is a difference how would you characterize it? People who are not audio experts are welcome to give their opinion.

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    Jan 23 2013: I'm no audio expert, but I suspect it has something to do with dynamics or miniscule but powerful 'spikes' in sound. The live sound of your mother's voice has free-range dynamics, whereas a recording of her voice would be dulled down, or clipped, in the recording/playback equipment's electronics, microphones, and speaker cones.

    I don't think it has much to do with a frequency range mismatch. (recording equipment and human hearing - both, I think, are roughly in the range 20 - 20,000 hertz). The problem seems more to do with the dynamics of volume...?
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      Feb 10 2013: I agree that the recording would sound dull, Allan, but not sure it has to do with "slides" up and down in volume. Or maybe it does, the live voice hits more accents, and the recording flattens them. Why would the equipment dull it down?

      There's something else, though, if a sound sounds "bright," what does that mean in technical terms? I wonder if a recording actually takes all sound a little bit toward the bass register? I kind of want to say that all the recorded stuff sounds like it's slightly coming through a very fine cheesecloth. Maybe the enunciation of any recorded speaker is not as sharp as a live one. Or recorded sound all sounds like it's coming through a "fog." Wonder what causes that?

      Have you had any more thoughts on this? I still don't feel I've gotten it, although with your help I'm closer. Please see my conversation with Lejan . above.
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    Jan 24 2013: This seems to me an audio version of the Turing-Test and an interesting question. :o)

    Assuming the best possible audio equipment and no knowledge about the damping characteristic of the given environment, in which the indirect sound travels through and therefore changes, I assume there is no way to distinguish in between a real and a recorded voice of a person.

    If the frequency reproduction of the speaker system was imperfect and even known, it may not be traceable due to the general distortion by damping, propagation delay and echoing in between both rooms, as it overall characteristic changes.

    So only if the whole environment was measured in its damping behavior throughout the whole noticeable frequency band of the human ear, we would then know about the changes to somewhat reconstruct the original sound source.

    Yet only very dominant speaker imperfections in certain frequency bands were detectable this way for the 'backward calculations' to 'find' them within the sound-field changing environment, as we may get to little equations for to many unknown variables.

    The easiest way to be certain about the presence of our mothers in the other room was just to go and see for them ..., even though this takes away the whole technical challenge ... :o)
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      Jan 29 2013: Lejan ., I hope I don't disappoint you in my reply. I think my goal here might not be as theoretical as you might have perceived it. My question is not about the best possible audio equipment, but about ordinary audio equipment, and the goal is to become more articulate and aware about what everyday sounds does to me, or others. I'll put the question another way. Let's say you were watching your ordinary TV and hearing a fictional drama. Then let's say the actors from the drama could be magically transported into the room where you were watching TV, and say the same lines the same way, live in front of you. How would they sound different, because I think they would. The best I can get at is that they would sound brighter, sharper, crisper live, that the sound through speakers sounds dulled down as Allan mentions below. But if you can say anything more about how the two sounds would differ, it would be much appreciated.

      Always I have this slight wish to free myself from technology, for example here in the States the average person watches TV six hours a day, and it seems wrong! Perhaps by studying sound I can free myself a bit from the attraction of the mechanical entertainments. Where are you on technology, pro, anti, mixed? Why?

      Interestingly, I think even on the best audio equipment available, you will find a difference between live sound and recorded.
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        Lejan .

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        Jan 30 2013: Hi Greg,
        there is nothing disappointing to get a better understanding of your question even though I have to admit that I probably danced to often to close to very loud speakers, so that my ears won't sense any difference between a recording and those magical guests in my living room... :o)

        Also I have no TV, as I found myself only listening to it in the background while doing other things, so I switched to a radio and use less electrical energy this way.

        The most realistic recordings I have ever heard were binaural ones, which are best by using earphones.

        If you are interested, have a 'hear' to this samples:


        For comparison, here is the same song as a usual stereo recording:


        And some classical piano music:


        In terms of '3D space' and the use of ordinary audio equipment, this is the best you can get.

        I have no idea why binaural recordings did not become a standard in the music industry, especially today, were many people listen to music via headphones and their mp3 player...

        On technology I am quite mixed and it just depends on the application and its use and has the whole grey-scale from anti to pro.

        I hope your studies will bring you a better understanding of sound and maybe a visit at your local theater closer to the magic of live performance... :o)

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          Feb 10 2013: Apologize, Lejan ., still haven't listened to your links, for a while no linking capacity was working, plus the headphone jacks weren't all working at the public library where I use computer (don't own my own). Sorry your hearing damaged, what sort of music were you dancing to?

          But since I really value your opinion, try to cast your mind back to perfect hearing times. It doesn't have to be actors, or magically transported, or the other room. If you and your friend sat in a room with average recording equipment; you recorded him saying something and played it back and listened to it; then he said the same things live, in the same way, he said on the recording: would it sound different, and if so, how? Do you agree that the recording would sound duller, and the live voice brighter? Can you add to the description of difference? Do you agree that refining your sense of hearing, of sound, of becoming more articulate about sound, is a very valuable skill?

          Please reply above. Eventually I'll get to your links.