A method to develop inexpensive inorganic polymeric sensors that can provide a sensitivity and selectivity for explosive nitroaromatic compounds. The LED lamps activated in excess of 120 times per minute is visible at distances in excess of one mile. A humidifier humidifies the oxidant prior to delivery of the oxidant to the cathode inlet. A brightness control plate is interposed between the lower polarization plate and the DBEF to reduce the brightness of an inclined incident light that is not perpendicular to an absorbing axis of the polarization plate. The method comprises applying at least two speech enhancement processes to produce at least two enhanced digitized speech signals and computing a coded speech signal by processing the at least two enhanced digitized speech signals.