The lowest frequency at which the device produces audio. The lower the low-frequency response, the stronger and juicier the bass.
The highest frequency at which device produces audio. The higher the high-frequency response, the clearer and crispier the treble.
3.has passive noise reduction
The device sits tightly in place, creating an acoustic seal which reduces background noise and prevents your music from leaking out.
Devices with a higher sound pressure level are generally louder when supplied with any given audio source.