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Homeowners can also opt out of Phase 2 removal and independently manage cleanup.

"Two waves can either add up if they are exactly in phase or they can cancel each other if they are exactly out of phase. That's kind of what's happening here though we're talking about faint sounds that would barely be audible to a human."

The study also implies that eastern Tibet was elevated prior to approximately 15 million years ago and the timing of fluvial incision may be out of phase with the growth of plateau topography.

If, however, the waves of light are out of phase and overlap while misaligned, a peak may meet a trough in the wave, and both are canceled out, a process known as destructive interference.

With drawings of the performers by Mr. Rosenbaum and photos of them by Ms. Newmark Rosenbaum, it depicts a place and a culture that seems beguilingly out of phase with modern life.