Hemi-Sync needs headphones. Binaural beats are the byproduct of how your brain perceives the nuances of stereo phasing: slightly different tones are played into each ear and your brain perceives the difference of the tones as a beat frequency. With headphones, the left channel is fed directly into the left ear while the right channel is fed directly into the right ear, and then your brain does the rest of the work. 

The Most Important Feature

When buying headphones to listen to binaural beats, consider comfort first. It’s likely that you are meditating, sleeping, or focusing on something and in any of these situations, discomfort will reduce the effectiveness of the binaural beats. Personally, I choose an enclosed headphone with comfortable padding so that I can block out the outside world. Technical features are secondary, but once I settled on a comfortable type of headphone, I would then look for qualities like dynamic range and frequency response.

Recommended Headphones

I use three kinds of headphones: earbuds for use with my iPhone, AKG K-240 Studio Headphones around the house, and the Sleep Sonic pillow for when I’m lying down and planning on sleeping.

Earbuds

Although you might question the sound quality of earbuds that are common with iPods and iPhones, in my own experience they work well with binaural beats, and certainly the iPhone 5 specifications indicate a frequency response somewhere in the range of 20 Hz to 24 kHz, which not only beat expectations from consumer electronics at any level, but the playback specifications are better than your ability to hear.

Earbuds will work fine.

When I am traveling, I use earbuds with my iPhone. They are not the best quality and they are uncomfortable, but they are convenient — and, believe it or not — earbuds are good enough to listen to binaural beats and music enhanced with brainwave entrainment technologies. The most popular earbuds for use with binaural beats and Hemi-Sync® are the Sony MDREX310LP In-Ear Headphones.

One reader commented that he likes the Beats by Dre Ear Buds, but I have yet to try these myself.

Headphones

Most often, I use the AKG K-240 Studio Headphones. They are enclosed so they partially block out external sounds, they sound incredible and they have only one cable so that I never feel trapped inside a bunch of wires. Also, they feature an adjustable fit that feels great. Another popular pair of headphones is the Sony MDR10RDC Premium Digital Noise Canceling Headphones. I used these for several years before switching to the more natural sounding (and more affordable) AKGs, but the Sony’s have proven to be quite popular for listening to binaural beats. The Sony headphones also have a strong bass response, which many people like.
If you like a lot of bass, I also recommend the Sennheiser HD 202 II Professional Headphones. I find these at radio stations: they are very affordable and have the strongest bass response I’ve ever come across.

Sleepsonic® Pillow

For the most part, I meditate in an upright position but sometimes I change things up by lying down. In this case, I really like the Sleepsonic® Pillow. It is extremely comfortable, it allows me to lie down without clunky headphones getting in the way and these great little speakers don’t block my hearing like my earbuds or enclosed headphones.

Sleep Phones

Honestly, I have yet to try the SleepPhones headbands, but they come highly recommended from a good friend. Essentially, they are headbands that fit comfortably over your ears. They come in a variety of colors and sizes and based on the customer reviews at Amazon.com, they are highly regarded by the people that use them.