Cordless headphones require some source of power. Many use rechargeable batteries and those can be recharged by returning the headset to a recharging base, much like what you might do with your cordless telephone. The amount of time that you can listen with fully charged batteries varies from model to model. The average listening time might range from 2 to 4 hours, per charge. They perform within a given frequency range.
Frequency response refers to the lowest and highest audio frequencies headphones can reproduce.
Frequency response is measured in Hz, which represents a sound wave cycle per second. The optimal frequency response of the human ear is 20Hz to 20,000Hz. Most headphones meet or exceed that frequency range. Headphone models made by these manufacturers may be designed for compatibility for best performance with these bass-enhancement technologies. Most headphones now include an adapter that allow connection to either sized port.