The **Perceptual Evaluation of Speech Quality (PESQ)** is an [[objective test]] that uses an algorithm to estimate the quality of the output speech by comparing it to a reference speech signal. It computes a score based on the perceptual similarity between the output and reference speech. PESQ takes into account several factors that affect speech quality, such as spectral distortions, temporal alignment, and noise level. It uses a model of the human auditory system to simulate how a listener would perceive the speech signals. The output of PESQ is a score between -0.5 and 4.5, with higher scores indicating better speech quality. PESQ is commonly used in the telecommunications industry to evaluate the performance of voice communication systems, such as cellular networks and VoIP services. It can also be applied to other applications that involve synthesized speech, such as text-to-speech systems and speech recognition.