Very unexpected waveforms with Realtek/Creative SB

[guidox]

Give a look here:
http://www.tech-archive.net/Archive/Dev ... 00056.html
Guido
I use Window XP
Very interesting too:
http://www.head-fi.org/forums/f7/phase- ... on-261277/

[steve]

Very interesting too: m http://www.head-fi.org/forums/f7/phase- ... on-261277/

As I said, it generally doesn't matter. The writer who suggests that the sound from a drum should start with a " strong once-off wave which should be translated to airwave towards your ears to have desired impact" sounds reasonable, but is not correct. In the case of a drum being hit, for example a snare drum, the impact of the stick on the head of the drum will cause the skin to move down, thus creating a eduction of air pressure in the atmosphere above the skin, and as the drum skin vibrates, this will oscillate between compression and expansion, creating a sound wave. However, the bottom of the drum will move downward from the initial stick impact on the top skin, causing a compression in the atmosphere (opposite of the top skin). In addition to this, the skins do not simply move up and down, but vibrate in multiple directions creating complex sound waves. Further complicating is the effect of the snare vibrating against the bottom skin, and reflections of the sound from other objects in the room, resonant vibrations from other drums, and many other factors.

The sound that is actually heard is thus a complex mixture of compressions and rarefactions that are transmitted through the air in all directions, finally being heard when they reach the ears of the listener.

Another factor to consider is that for any specific frequency, the phase will change depending on the distance between the sound source and the receiver (the ears). If you listen to a sine wave and you are exactly half a wavelength away from the speakers, the sound you hear will be inverted relative to the movement of the speaker.

You can easily do an A/B test for phase reversal. Record or import some music into Audacity. Make a duplicate copy of the track and use the "Invert" effect from the effects menu. Listen carefully to the two versions (also notice that if you play both tracks at the same time you get silence). Now get an assistant to play one of the tracks to you and see if you can identify whether it is the original or inverted version.

[guidox]

You can easily do an A/B test for phase reversal. Record or import some music into Audacity. Make a duplicate copy of the track and use the "Invert" effect from the effects menu. Listen carefully to the two versions (also notice that if you play both tracks at the same time you get silence). Now get an assistant to play one of the tracks to you and see if you can identify whether it is the original or inverted version.

[/quote]

YES.
I took several and different tracks (classical, voice singer, voice speaking, jazz, testing sounds, other...) and after many "hearing tests" I would say that "NO real audible DIFFERENCE".
Guido