Binaural beats work by playing slightly different frequencies into your ears. When your brain tries to resolve the minor difference between the two beats you're hearing, they take you quickly and effortlessly into the brainwavelevel that you've decided to listen to.

In case you want to program your own, the frequency range for Theta is between 4 and 7 Hz.

Various trials have shown that this level encourages your brain to make the "feel good" things called endorphins.

One of the other reasons for choosing the theta level when you consider buying a binaural beats MP3 is that they are generally considered to help with learning. Studies have also shown that people listening to them on a regular basis find that they need less sleep - reports vary from between one and four hours less, depending on the person.

Because the theta frequency level is associated with dreaming, you may well come across them when you are searching for items to help you dream - whether that's lucid dreaming or just the quest to banish sleepless nights.

Theta level binaural beats are also associated with increases in memory as well as learning that was mentioned earlier. Because of the way they operate, this can help you to learn topics when other methods haven't been successful.

Research shows that children spend a lot more time with their brains in a theta state than adults do. Which helps to explain why children can soak up information as though they were a sponge, whereas adults can often take longer. It's kind of the same as the saying "you can't teach an old dog new tricks". Maybe the equivalent in humans is at least in part to do with a lower level of theta brainwave activity.

You may also come across binaural beat MP3s and CD that use the alpha brainwave level for learning - this works as well as the theta level. So don't panic if you come across different levels of brainwave entrainment being used to the same thing.

Quite a lot of the experiments to prove the effectiveness of binaural beats have been done by an organization called the Monroe Institute. They tend to combine their use with other systems, such as hypnosis.

One thing to be aware of if you are buying any sort of audio with binaural beats included is that the compression used should be as low as possible. Technologies such as MP3 are designed to compress file sizes by cutting out parts of recordings that we don't normally listen to. Typically this includes things such as binaural beats. So you need to make sure that you're getting what you think you're purchasing. It's often better to wait a few days for a CD to arrive but if the download you're looking at is large, chances are that it will also be uncompressed.