Multisensor MELPe using parameter substitution

The estimation of speech parameters and the intelligibility of speech transmitted through low-rate coders, such as MELP (mixed excitation linear prediction), are severely degraded when there are high levels of acoustic noise in the speaking environment. The application of nonacoustic and nontraditional sensors, which are less sensitive to acoustic noise than the standard microphone, is being investigated as a means to address this problem. Sensors being investigated include the general electromagnetic motion sensor (GEMS) and the physiological microphone (P-mic). As an initial effort in this direction, a multisensor MELPe coder (MELP coder with the addition of a noise preprocessor) using parameter substitution has been developed, where pitch and voicing parameters are obtained from GEMS and P-Mic sensors, respectively, and the remaining parameters are obtained as usual from a standard acoustic microphone. This parameter substitution technique is shown to produce significant and promising DRT (diagnostic rhyme test) intelligibility improvements over the standard 2400 bps MELPe coder in several high-noise military environments. Further work is in progress aimed at utilizing the nontraditional sensors for additional intelligibility improvements and for more effective lower-rate coding in noise.