Voice Feedback Control with Subject-in-the-Loop

A subject-in-the-loop feedback control system is composed of a bioengineering system including a subject, whose voice is received by a microphone, a computer that achieves the required signal processing of the sound signal by temporal and/or spectral computations and a speaker or earphones for auditory feedback to the subject of voice training. Frequency domain modifications of the signal are intended for voice training of subjects already familiar with traditional voice training. The objective of this paper is to present alternative methods for the implementation of subject-in-the-loop feedback control systems developed for voice training. The proposed feedback control scheme is an extension of the traditional control systems; feedback sensing and the control law are achieved by the human subject as a self-organizing controller. The experimental set-ups, developed for this purpose, contain programmable digital devices for real time modifications of the frequency content of the voice signal. The paper presents also a preliminary solution that satisfies the requirements for real-time operations, in particular that the subject does not perceive the delay between the sound generation and the auditory reception of the modified sound. The system performs spectral calculations for the analyses of the vocal sound signals. Preliminary experimental results illustrate the operation and the features of the proposed subject-in-the-loop real-time system for voice training.