The average person slips in and out of Alpha from 5 - 30 times a minute. Gifted and creative people tend to spend more time than usual on alpha waves even though they may be engaged in intensive work or study work best when their minds are relaxed. It is the difference between psyching yourself up for something or just letting it happen. Hz indicate the brain is focused on a problem, or intense concentration. Beta waves are also associated with tension and anxiety.
Heavy smokers generate large amounts of beta activity and very little alpha activity.
The Brain also tries to match artificial man made signals. Most electric appliances work off of 60 Hz or higher in North America and 50 Hz in Europe. Computer monitors operate at 20,000 Hz., Cellular Phones operate a 840 Million Hz., Microwave Ovens at 2.8 Billion Hz. The higher the frequency the more serotonin that's produced in the brain. Serotonin has recently been associated with cancer.