Safe Level Sound Compression Technology. Acoustic Foam for All Day Comfort. Sound Refresh Time <1ms. 2 Full Dynamic Range High Definition Speakers. 2 Omnidirectional Microphones. 3x Amplification. 200-Hour Runtime for Models 40978 and 40979. 3 Hour Automatic Shut Off. Noise Reduction Rating of 22 dB . AAA Batteries Included.