Noobie-doobie questions about phase

[rbet]

I have these two sound files made for testing purposes. The sound file consists of two tones, one at 500Hz and the other at 100Hz. They are both the same, except in one file, the left channel is out of phase with the right channel.

I think I know what that means, let's see if I have it right. 'In phase' means if I draw the amplitude of the sound file against time for both channels, the graph will be the same for both the channels (i.e, they will coincide) for the 'in phase' file. For the 'out of phase' file, however, it means that the graph for one channel will start a little 'late', i.e., the nature of the graphs for the two channels will be the same, it is just that the graph of one channel will be shifted to the right (or the left depending on how you look at it). Am I correct?

My problem is that in the 'in phase' file, I can hear both tones clearly, while in the 'out of phase' file, I can hear the 500Hz tone, but can barely hear the 100Hz tone. The spectrum analyzer outputs of both the files are identical from what I see. I don't understand what this means for me. What do I do to correct the problem, if it is indeed serious? What is to blame (speakers, soundcard, other?) [Equipment used: Logitech Z-3 2.1 speakers, Soundmax Digital onboard audio. Don't laugh.]

On a related note, isn't this what 'mono' and 'stereo' sound is about? (Correct me if I am wrong)Mono means that the output of both the channels is the same at any time. Stereo means sound from one of the two channels reaches one of the ears later than the other, right? So, my question is, can mono files be panned *by nature*? I mean of course, we can physically do it in any host by playing with the panning knob, but can mono files have different outputs levels in left and right channels by themselves?

Does 'out of phase' automatically imply 'stereo' sound?

Sorry about the not-so-well-thought-out post. I am cunfyooz'd.

[C00kie]

You can swap the phase (negative becomes positive & vv) or delay one of the tones a bit to correct a phase problem.

Tiny delays between left & right do indeed account for perception of direction of sound. Most stereo enhancers work on basis of this phenomena.

Mono means you only have one channel. To get proper mono, you actually need to disconnect one of your speakers. If you feed the same signal to both left & right, I'd call that "double-mono". Once you set the levels differently by using panning, it has become stereo.

[rbet]

You can swap the phase (negative becomes positive & vv) or delay one of the tones a bit to correct a phase problem.

I thought that would mean changing the 'polarity' and not the 'phase'? Or are they the same?

Thanks about the mono-stereo bit.

[Meffy]

Yup -- if the waveform's symmetrical top-for-bottom, a 180-degree phase shift is the same as inverting polarity. But not, for instance, if you have a 10%-90% duty cycle rectangle wave. (You'd be able to see the diff on an oscilloscope but the inverted and phase-shifted waves would sound the same in isolation.)

[C00kie]

You're right, swapping polarity is the same as offsetting the phase by 180 degrees. Within certain definitions that is, but I'm not going to split that hair.

[Meffy]

I already split that hair. :-D I should also point out that inverting will turn a sawtooth into a ramp, etc. But again they'd sound the same. (At least I don't know anyone who can tell the difference by ear.)