The manufacturers of most of our cardio equipment have not changed their technology to adapt to today’s headphone jacks. Specifically, if your headphone jack has three black rings on the end that plugs into the machine, you may not hear anything, or it may be hard to hear or scratchy. The older model headphone jacks have two black rings on the end which should plug into our machines with better sound. Alternatively, most of the newer machines allow you to connect via Bluetooth if your headphone device allows. You must have the charger with you to connect to the Bluetooth for the specific machine.