Originally Posted by
schmidj
Off hand I can think of three causes of pops or clicks at the beginning (or end) of your music tracks. All of them involve the player not the actual rip. Two of them result in what are sometimes called "Fourier clicks or pops". More on that shortly. The third one is if the player is stupid and tries to play the tag data as audio.
Now back to the first two. For a deep understanding of this you need to understand Fourier's Theorem and what it tells you about what you hear. But I'll try to explain in simple terms. Basically, if there is a sudden change in amplitude in a short period of time, the theorem says that there is significant high frequency content present at the instant of the change in amplitude. You may hear that as a click at that moment. And if there is an edit from silence to audio at a moment where the instantaneous voltage of the audio is not zero (called a zero crossing) or worse still, there is DC offset with the audio (The AC voltage of the audio is riding on a DC voltage, usually due to a circuit defect), you will usually hear a pop or click at that point. Most good audio editors give the option of making the actual edit point at a zero crossing near the point you chose to reduce the audibility of Fourier clicks or pops. But it could be unselected or not available in your editor. Note that you still may get an audible click on an edit at a zero crossing, but it usually is much less audible.
Now why you don't hear it on a CD. Because most if not all CD players actually fade the audio in when you hit "play". The click happens before the audio is turned up. That is why most CD tracks that aren't "gapless" between tracks are made with nothing of consequence (like the first note) in the first fraction of a second. If the music started hard at the cue point, the first note would be "upcut".
While most CD players may fade into the track (but only the track where you start it, not the later tracks when you play the whole CD), apparently some digital file players don't fade in, and digital editors shouldn't fade in, as you want to hear everything from the play point. So you hear the pops.
In addition to having silence at the start, most audio tracks are edited with a brief fade at the beginning, specifically so they won't have a pop. But you don't want to do that with tracks that play without a break. like live concerts, because then they would have a brief dropout between tracks. That is why it has to be the player that fades in when you press Play, not the ripped track.
Sorry, this is all physics and math.
Actually, there is another thing I've seen on poorly produced CDs, usually homemade CDRs. And this applies to individual tracks, not "concert" albums. I've run into some where the index point for the beginning of the track is mis-located, so the end of track 1 actually plays at the beginning of track 2 or the other way around. That's the fault of the CD manufacturer. Because the CD player fades in, you might not hear it when playing the CD, but if you rip the CD and look at the waveform on an editor, it is very visible.