 All electrical activity produces these waves (even light bulbs), thus all electrical devices create some level of ambient “noise”; this “noise” interferes with the waves emanating from the brain, this is why most EEG devices will pick up readings even if they are not on a person's head.Measuring mental activity through these waves is like trying to eavesdrop on a conversation at a loud concert.In the past, EEG devices circumvented this problem by measuring these signals in environments where electrical activity is strictly controlled and increasing the signal strength of the data coming from the brain through the application of a conductive solution.