Phase entrainment of neural oscillations, the brain's adjustment to rhythmic stimulation, is a central component
in recent theories of speech comprehension: the alignment between brain oscillations and speech sound
improves speech intelligibility. However, phase entrainment to everyday speech sound could also be explained
by oscillations passively following the low-level periodicities (e.g., in sound amplitude and spectral content) of
auditory stimulation—and not by an adjustment to the speech rhythm per se. Recently, using novel speech/
noise mixture stimuli, we have shown that behavioral performance can entrain to speech sound even when
high-level features (including phonetic information) are not accompanied by fluctuations in sound amplitude
and spectral content. In the present study,we report that neural phase entrainment might underlie our behavioral
findings. Weobserved phase-locking between electroencephalogram (EEG) and speech sound in response not
only to original (unprocessed) speech but also to our constructed “high-level” speech/noise mixture stimuli.
Phase entrainment to original speech and speech/noise sound did not differ in the degree of entrainment, but
rather in the actual phase difference between EEG signal and sound. Phase entrainment was not abolished
when speech/noise stimuli were presented in reverse (which disrupts semantic processing), indicating that
acoustic (rather than linguistic) high-level features play a major role in the observed neural entrainment. Our
results provide further evidence for phase entrainment as a potential mechanism underlying speech processing
and segmentation, and for the involvement of high-level processes in the adjustment to the rhythm of speech.