1. A method for monitoring a conversation between a pair of speakers for detecting an emotion of at least one of the speakers using voice analysis comprising the steps of: (a) receiving a voice signal representing voices of speakers in a conversation; (b) extracting at least one feature of the voice signal selected from a group of features consisting of a maximum value of a fundamental frequency, a standard deviation of the fundamental frequency, a range of the fundamental frequency, a mean of the fundamental frequency, a mean of a bandwidth of a first formant, a mean of a bandwidth of a second formant, a standard deviation of energy, a speaking rate, a slope of the fundamental frequency, a maximum value of the first formant, a maximum value of the energy, a range of the energy, a range of the second formant, and a range of the first formant; (c) determining an emotion associated with the voice signal based on the extracted feature; (d) determining whether the emotion matches a negative emotion selected from a predefined group of negative emotions consisting of anger, sadness and fear; and (e) outputting the determined emotion to a third party during the conversation if the emotion matches one of the negative emotions.