Several methods for electronic processing of reverberant sound signals to suppress echoes and reverberation are discussed. Potential applications of these methods in sound reinforcement, conference telephony, and underwater speech communication are described. The implications of a recently proposed self-adaptive echo canceler [M. M. Sondhi, J. Acoust. Soc. Am. 40, 1255(A) (1966)] for improving the stability of sound-reinforcement systems are considered.