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The most frequent sounds heard on WWV and WWVH are the seconds pulses. These pulses are heard every second except on the 29th and 59th seconds of each minute. The first pulse of each hour is an 800 ms pulse of 1500 Hz. The first pulse of each minute is an 800 ms pulse of 1000 Hz at WWV and 1200 Hz at WWVH. The remaining seconds pulses are short audio bursts (5 ms pulses of 1000 Hz at WWV and 1200 Hz at WWVH) that sound like the ticking of a clock.
Each seconds pulse is preceded by 10 ms of silence and followed by 25 ms of silence. The second marker for the broadcast is at the end of the 10 ms period and the start of the 5 ms period. The station's on-time marker is synchronized with the start of the 5 ms tone. The silence before and after the pulses makes it easier to identify the second pulses. As shown in the graphic below, the total zone around the second pulses lasts for 40 ms, consisting of 10 ms of silence, the 5 ms tone, and another 25 ms of silence. Then, the standard frequency audio tones resume.