You shouldn’t hear any changeover at redline, that’s for damn sure!
As for the others… that’s likely just the harmonics of the engine note, really. The whole point of variable timing control is that the engine is ALWAYS adjusting timing, not only at set rpm intervals. This “on-the-fly” adjusting ensures an optimization of the engine’s power throughout the rpm band… so it’s like a going up a smooth hill, not a series of steps.
If you want to know what actual VTEC is supposed to sound/feel like. Step into an old Integra GSR, or an S2000. You’ll not only hear the diff., you’ll REALLY feel it. Same with the new Civic Si; only this car has VTC (variable timing control), so it shouldn’t be a pronounced changeover, but because so many people complained that it was too smooth on the RSX-S, Honda engineered a forced audible “bump” at 6000 rpm just to please the ricers. 