DRAMATICALLY REDUCES MOST LOW FREQUENCY DISTRACTIONS FROM AIRPLANES\, LAWN MOWERS\, FANS OR EVEN THE DIN OF AN OFFICE; OPERATES WITH OR WITHOUT ACTIVE NOISE-CANCELING CIRCUIT ENGAGED ; FREQ RESP: 20 HZ-20 KHZ; IMP: 32_; SENSITIVITY: 100 DB SPL; REMOVABLE 4-FT CORD FEATURES IN-LINE VOLUME CONTROL ; 1 STANDARD AAA BATTERY PROVIDES APPROX 50 HOURS OF ACTIVE NOISE CANCELLATION; NO-QUESTIONS-ASKED LIFETIME WARRANTY