Hi

There are a number of theories about the 9 minute cycle of a snooze button. Some believe that it takes approximately ten minutes for the average person to reach what is called Stage 1 sleep, essentially a quick dozing off. In fact, the first alarm clock with a snooze button, introduced in the 1950s by General Electric, offered either a five minute or ten minute snooze button option. It was only when the LED alarm clocks became popular in the late 1960s that a 9 minute snooze button cycle became commonplace.

Another theory about the snooze button cycle is that engineers looked at earlier alarm clock models and decided that 9 minutes was a good enough standard to follow. Studies conducted on volunteers supposedly indicated that most sleepers wanted anywhere from five to ten extra minutes of sleep, so anything under ten minutes should be acceptable. It's not unusual for heavy sleepers to hit the snooze button several times anyway, so they would be actually be getting nearly a half-hour of additional sleep.

Thanks