46 U sing Lo gi c P r o's Sy nthe s iz er s terms of percentage. A 50% pulse wave is also called a square wave--the length of the peak is equivalent to the length of the trough. In other words, 50% of the time, the wave is in a peak, and 50% of the time, the wave is in a trough. While a square wave contains only odd harmonics, as you deviate from the square wave into rectangle pulse waves, even harmonics appear. Because we don't hear which part of a wave is a peak and which is a trough, a 60% pulse wave sounds identical to a 40% pulse wave. Figure 4.4 shows a rectangle pulse wave in the Sample Editor.