The Koss QZ-77 Active Noise Reduction Ear Plug System combines active and passive noise reduction technologies to suppress a wide range of ambient sounds. Its built-in active circuitry targets low-frequency noises such as engine rumble and HVAC hum, while the memory-foam ear tips provide passive isolation against mid and high-frequency disturbances. The ear tips are made from slow-recovery foam that conforms to the ear canal for a secure and comfortable fit, enhancing both noise reduction and audio clarity. The product features dynamic drivers covering a 10–20,000 Hz frequency range and is designed with a lightweight, compact housing suitable for frequent travel and commuting.