Noisebuster® Electronic Noise Canceling (ENC) earmuff from Pro Tech protects against a wide range of noise frequencies, especially low-frequency noise generated by industrial engines, motors and fans. The earmuff can be worn over the head (26dB NRR) or behind the head (25dB NRR). ENC component gives up to 20dB of added noise reduction within low-frequency bandwidth of 20-800 Hz.Pro Tech Communications, Inc., Fort Pierce, FL.