Misconception about Phasing

Discussion in 'Microphones (live or studio)' started by Cucco, Nov 3, 2004.

  1. Lobe

    Lobe Guest

    Well I don't mean to squabble over this but the longer waves do indicate low frequencies and the shorter ones do indicate higher ones. This is a fact. The two waves you show do look like an ocatve apart and the lower one being roughly twice as loud. Of course you can't spot which little squiggly part of the wave is a piccalo amongst the sound of an orchestra but looking at a sample of a piccalo against some sub bass samples I would expect to see contrasting wave patternes (generally short and long) for these instruments.
     
  2. Cucco

    Cucco Distinguished Member

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    Mar 8, 2004
    Location:
    Tacoma, WA
    So how do you account for the thousands of frequencies present at any given point - there certainly are not thousands of frequencies represented in a DAW window...
     
  3. Randyman...

    Randyman... Well-Known Member

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    Location:
    Houston, TX
    I didn't read the whole thread, so at the chance of looking like a complete idiot, here is my take. (I look like an idiot anyway ;) )

    I thought the DAW display of a waveform would essentially represent what the speaker would be doing (or what the mic's diaghram was doing when it captured the analog signal)? A speaker's cone can obviously NOT be in 2 places at one time, yet it is able to play pink noise and such.

    Once you add more than one "pure tone", you will STILL have one waveform, but with the higher tone "riding ontop of" the lower tone (also increasing the RMS level of the composite waveform). So you can see the low tone as a longer wave, and the high tone is represented by ripples within this low tone, right? So, you can NOT see each individual frequency, but the overall effect of the constructive and destructive addition of the individual pitches (or addition of multiple tracks). OK - Now tell me how I was wrong :oops:

    :cool:
     
  4. Cucco

    Cucco Distinguished Member

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    Randyman,

    You are essentially correct - but again, it's important to understand that ALL the frequencies cannot be represented. So while you are seeing a representation of frequency, it's a summed representation. And as you state, the cascading frequency creates an increase in amplitude.

    Imagine if two frequencies are being performed simultaneously that are only 2 Hz apart. One couldn't ride on top of the other in the window, and it certainly would not draw both - hence the summation of the amplitude of the frequencies.

    Thanks,

    J...
     
  5. Randyman...

    Randyman... Well-Known Member

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    Jun 1, 2003
    Location:
    Houston, TX
    Got it.
    Kind of like trying to "see" all of the frequencies of a guitar by simply watching a guitar string vibrate? (Which, of course, you can not see). Or, like standing in a room with a guitar AND a bass. You will hear both at once, but you will be hearing whatever constructive and destructive interference occurs at your ears (only hearing "one" waveform, but portraying 2 distinctly different waveforms)


    Cucco is one cucco-ly-coolio dude :)
     
  6. sammyg

    sammyg Active Member

    Joined:
    Dec 12, 2003
    hey guys,

    I read an article on phasing which stated that if you are constantly working in the audio field, production or whatever, you should check wiring specs on new leads and equipment you buy to make sure they all conform to the one standard, curious to know, does any body do this as common practice, or do most guys just assume that most manufacturers agree on what is considered "industry standard" and build according to this protocol.

    Has anyone had some funny encounters??
    I must confess, I have never checked any of the gear I have purchased, or leads for that matter to see if they all conform with one another, maybe purchasing "pro" products makes us think,
    " hey, I dont have to check, they know what they are doing.."


    Sammyg
     
  7. Thomaster

    Thomaster Guest

    emm Cucco (please dont flame me, im only 20 and still learning by asking silly questions)

    its not possible to make a visual representation of everything that happens in the air and is caught by a microphone. of course not.

    but one thing i dont get:
    why would anyone want to have a perfect graphical representation of what happens in their DAW?
    i mean to ask:
    if you want to phase-align in your daw (cuz i think thats what started this thread) by shifting tracks so that they graphically align (at the lowest zoom-in-level)
    wouldnt it be enough to just nudge (either by hand/eye or by delay plugins/tools) the beginning of each track/sound?
    assuming that the instrument you're recording and the microphone are stable, (thus not moving back or forth from the source)
    that would mean that all of the track would be in phase with the other.

    also, assuming that frequency is in fact the same as amplitude (freq. is periods (thus amplitude) per second. doesnt the daw-interface in fact give us a representation of phase, i mean if you graphically align the amplitudes of two tracks, doesnt that mean you have the phase aligned as well?

    am i missing something?

    i guess essentially my question is: if i align a track to another that both have a lot of different frequencies, and i make sure that the beginning of each track starts graphically at exactly the same time, isnt it true that then they are in phase correctly with eachother



    bwaagghh i guess this post wasnt as clear as i wanted it to be
    sorry
     
  8. Cucco

    Cucco Distinguished Member

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    Location:
    Tacoma, WA
    Thomaster:

    Hey man, good question. Don't worry, I won't flame you. Do I have that bad of a reputation already?

    What you're asking about is essentially what I tried to dispell in the original post. Remember, the wave form displayed is one of amplitude and is an attempt to "combine" all frequencies into one wave form. As Randyman suggests, you wouldn't be able to see all the frequencies by the pluck of a guitar string, but you do get an overall idea of the sound by how much it vibrates.

    That being said, since the wave represents amplitude and not frequency (despite a lot of peoples desire to hold on to this misconception) peaks and troughs aligning does not an in-phase signal make.

    Truthfully, if you use some basic math and your ears, rather than depending on a rather sloppy visualisation, you will find that signals in general are easy to phase align.

    J...
     
  9. gnarr

    gnarr Guest

    why are you attemting to combine the frequencies in one waveform?? they are already in one waveform.

    i hope you know this already. but this wave:
    1hz.png
    plus this wave:
    2hz.png

    becomes a combination of both.

    example:
    wave.png
     
  10. Cucco

    Cucco Distinguished Member

    Joined:
    Mar 8, 2004
    Location:
    Tacoma, WA
    Gnarr,

    You are absolutely correct. However, try doing that with thousands of frequencies - it doesn't look so pretty now. That's where the limitation of the DAW is. It tries its hardest, but falls short. Yes, it attempts to draw frequencies, but the fact is, not all frequencies are represented.

    Thanks,

    J...
     
  11. RecorderMan

    RecorderMan Distinguished Member

    Joined:
    Mar 28, 2001
    haven't ANY of you guys heard of a fourier transform?
     
  12. Lobe

    Lobe Guest

    Thanks Recorderman.

    The theory is that the digital sampling process takes a snapshot of the sound pressure wave (as picked up by the mic for instance) every 44.1 thousanth of a second. If you have a DAW with an actual sample level visual display and you can zoom in close it becomes more obvious that you are seeing a visual model of exactly this data. With samplitude for the PC you can zoom in to make 4 samples fill a 17 inch monitor.

    You'd have to be a seriously autistic freak to be able to make sense of these waves but the theory holds that all the information is there. All the tiny detail of the noise floor waveform is there superimposed on the larger wave of the instrument you just recorded but of course it's impossible to tell it's there just by looking at it. But it is there.

    Look here for how the average DAW fish fin wave display breaks down into it's componant frequencies (of which there are many quiet ones and a few dominant ones)
    http://www.bores.com/courses/intro/freq/3_spect.htm

    The maths for this is mind boggling.

    If you look at a painting of a tree you see a tree. Look closer you can see the shape of the leaves. Analyze it with special gear and you could probably work out what the weather was like last winter and a few thousand other things despite the fact that to the eye it still just looks like a tree. The same holds true of these random looking waves. The devil is in the details.
     
  13. Thomaster

    Thomaster Guest

    thats true
    but still cucco is right (after i read his post i agree:))

    Fast Fourier Transform (FFT) on the contrary, displays a lot more information, like; the amplitude, length and frequency of all the different partials (overtones and fundamental) It is something that all daw's should have in their GUI's as an option.
    it holds way more info than the standard displays in Logic, protools, etc..
     
  14. RecorderMan

    RecorderMan Distinguished Member

    Joined:
    Mar 28, 2001
    that's not what I was alluding too..but this is ALL crazy. Just use your ears..you have MORE than enough info to make records, just do it.
     
  15. Thomaster

    Thomaster Guest

    you're TOTALLY right.
    :oops:
    but its nice to test my knowledge here. although it makes me look like a snob-wannabe :-?
     
  16. johnthemiracle

    johnthemiracle Active Member

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    afaican remember the original sound designer program from digi had that option where you could display a portion of the sound file you were working on in fft as a 3d visualization. i found this pretty useless, though. i think there are better concepts now including that one software that visualizes it using 2d diagrams in color. makes more sense to me this way...
     
  17. Thomaster

    Thomaster Guest

    yeah, the latter was the one i was referring to.
    its pretty handy to have that in a DAW.
    it saves a lot of time for me
     
  18. MikePotter

    MikePotter Guest

    From the original post:

    Remember - 1 foot = .88 milliseconds or 1 foot = .02 samples in a 44.1khz sampled track.


    I think you mean that 1 ft = about 50 samples. There's a "one-over" error in there somewhere!

    Mike
     
  19. Cucco

    Cucco Distinguished Member

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    Mar 8, 2004
    Location:
    Tacoma, WA
    Thanks Mike. You're absolutely right.

    Of course, this is also dependent upon the frequency too.
     
  20. J-3

    J-3 Active Member

    Joined:
    Jul 20, 2004
    Not to change the direction of the subject but I'm sill confused a bit. So is it wise or not to time align tracks in the daw? I usually zoom in on my drum tracks and align the overheads and rooms with the kick and snare. It seems to tighten up the bottom end. Also, I use a sub mic and a d112. (sub mic is the speaker mic) when I zoom in the d112 being closer to the beater is recorded sooner than the sub so I time align them. Again tightens up the lows. I always go thru and toggle all the phase buttons on all the drum tracks in the end and just go with what sounds best. Any direction would be aprreciated.
     

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