Listening with stereo headphones seems to be the best way to achieve the effects of binaural tones. One frequency goes to the left ear, and one goes to the right ear. Together these frequencies combine and create a middle frequency that is between the frequencies sent to the left and right ear. Additionally, these two frequencies will create amplitude that rises and falls between the two frequencies. This creates a steady beat or pulse perceived by the ear.
When headphones are not used, the two frequencies come already combined. This seems to be a less effective method of creating mood-affecting binaural tones. However, there are certain companies that are marketing this technology to the public and providing their software for use with or without headphones.
As is often the case with new research, several companies have attempted to profit off this phenomenon. There are apps for mobile devices as well as recordings that cover the tones with classical music. The main criteria that consumers should look for is whether the frequencies are sent separately through the left and right ear and if the frequencies correspond to a particular brain wave. The brain wave frequencies that have been studied and tested are beta between 16 and 24 Hz, and theta between 1.5 and 4 Hz.