Speaker Recognition by Machines and Humans: A tutorial review

Identifying a person by his or her voice is an important human trait most take for granted in natural human-to-human interaction/communication. Speaking to someone over the telephone usually begins by identifying who is speaking and, at least in cases of familiar speakers, a subjective verification by the listener that the identity is correct and the conversation can proceed. Automatic speaker-recognition systems have emerged as an important means of verifying identity in many e-commerce applications as well as in general business interactions, forensics, and law enforcement. Human experts trained in forensic speaker recognition can perform this task even better by examining a set of acoustic, prosodic, and linguistic characteristics of speech in a general approach referred to as structured listening. Techniques in forensic speaker recognition have been developed for many years by forensic speech scientists and linguists to help reduce any potential bias or preconceived understanding as to the validity of an unknown audio sample and a reference template from a potential suspect. Experienced researchers in signal processing and machine learning continue to develop automatic algorithms to effectively perform speaker recognition?with ever-improving performance?to the point where automatic systems start to perform on par with human listeners. In this article, we review the literature on speaker recognition by machines and humans, with an emphasis on prominent speaker-modeling techniques that have emerged in the last decade for automatic systems. We discuss different aspects of automatic systems, including voice-activity detection (VAD), features, speaker models, standard evaluation data sets, and performance metrics. Human speaker recognition is discussed in two parts?the first part involves forensic speaker-recognition methods, and the second illustrates how a na?ve listener performs this task from a neuroscience perspective. We conclude this review with a comparative study of human versus machine speaker recognition and attempt to point out strengths and weaknesses of each.

Introduction

Speaker recognition and verification have gained increased visibility and significance in society as speech technology, audio content, and e-commerce continue to expand. There is an ever-increasing need to search for audio materials, and searching based on speaker identity is a growing interest. With emerging technologies such as Watson, IBM's supercomputer [1], which can compete with expert human players in the game of “Jeopardy,” and Siri [2], Apple's powerful speech-recognition-based personal assistant, it is not hard to imagine a future when handheld devices will be an extension of our identity—highly intelligent, sympathetic, and fully functional personal assistants, which will not only understand the meaning of what we say but also recognize and track us by our voice or other identifiable traits.