Aerial7 Sound Disk ODYSSEY Sports Beanie Headphones Headset with Built-In In-Line Smartphone Microphone for iPhone and BlackBerry, 51150 (Orange) Impedance--The opposition to electric current, a higher impedance means a higher electrical resistance. This is measured in ohms. 32 ohms Sensitivity -- An efficiency or sensitivity rating tells you how effectively a speaker converts power into sound. The higher the number, the more efficient the speaker and the louder it will play with the same input power. An efficient speaker helps you maximize your available power. Most sensitivity ratings measure the speaker's output with 1 watt of input, 1 meter from the speaker. Some speakers' sensitivity is measured with 2.83 volts of input, instead of 1 watt. Efficiency (1w/1m) is not an accurate indicator of a subwoofer's output capability and should not be used as a comparison to other speakers or subwoofers to determine which one is "louder". 100 dB Driver Size -- This refers to the diameter of the driver (speaker) on each side of the headphone. 32 mm Frequency Response -- The range of frequencies the speaker will reproduce (lowest frequency to the highest). Bigger is better, meaning the wider the range, the better. The optimal range is 20 - 20,000 Hz (which is the range of human hearing). 20 - 20000 Hz