Voice activity detection system for smart earphones

This paper presents a real-time voice activity detection (VAD) algorithm implemented in a miniature Digital Signal Processor (DSP) for in-ear listening devices such as earphones or headphones. This system allows consumers to hear external speech signals such as public announcements or oral communication while listening to music without removing their listening devices. The proposed algorithm uses two normalized energy features that compare the energy in the frequency region containing speech information with the frequency regions typically containing noise. The extraction of the normalized features represents the key of the proposed VAD since it eliminates the need for a signal-to-noise ratio (SNR) estimator. The VAD´s decision is made using two threshold comparison rules computed from the normalized features and a hangover scheme triggered after a given number of observations. The algorithm parameters, namely the frequency regions´ boundaries, number of observations, two decision thresholds and hangover´s duration, have been optimized offline using a genetic algorithm. The performance of the proposed VAD is compared to a benchmark algorithm in four noise environments and three SNRs. Results show that the average false positive rate (FPR) of the proposed algorithm is 4.2% and the average true positive rate (TPR) is 91.4 % compared to the benchmark algorithm which has a FPR average of 29.9 % and a TPR average of 79.0 %. The proposed VAD is implemented in hardware to validate its reliability and complexity.