NowI must say these things are the best.
Around 20 weeks babies start developing their hearing and close to 27-30 weeks they develop cognitive memory and recognizing voices. I love these belly buds because of the amazing features and app to sync all your recordings and music they have. You can record your own voice memos or even share it with family/friends to make their own that you can playback. You can even read stories, sing songs, purchase stories/songs or create playlists. Personally I've used this mainly to play his music and created my own playlist with classical music and gospel music. I even created a personal "Good morning" track where I'm singing a song to him that I grew up hearing. These songs can be as long as you want. One thing I do notice is when he is very active and I play this music it does settle him from kicking so much or after I eat when I'm napping or before bed, playing his music for about 15-20 minutes. A bonus is that you can listen to the music that the baby is listening too and adjust the volume. The buds come with a splitter so you can plug both your headphones in along with the headphones that go on your belly. The buds themselves have a sticky adhesive that you can place anywhere on your belly. It includes an extra pair so that if the stick runs out you can replace and change it. This is very useful during light workouts. Some cons is that the audio jack is not compatible for an iphone so you will need an adaptor to plugin to your phone. You also can't really run with them on either. The adhesive sticks but is not strong enough to hold if you are doing intense workouts. Other than that if you are wanting to play some calming music for your little one, this is a great purchase!
Check below for a peep inside the "Voice Share" app: