Is it possible for a device to emit brainwave frequencies that will put the brain to them?

K so you have the human brain which is always in different mind states such as Beta, Alpha etc which are all measuredin hz but is it possible for a device or something to emit hz frequencies that will actually bring a brain to that cycle? for example if something gave out a 7hz frequency (Theta) would the concsious mind fall into that 7hz mind state after a while? can it be possible for brainwave frequencies to actually me emitted and work on a brain is what I am asking. Thx.