Supplemental Audio 3. Binaural unmasking at low frequencies, version 1 (listen over headphones). A noise is played. Listen carefully for faint pulsed tones mixed in with the noise. Toward the end, the noise is faded out and the tones become clearly audible. Two tones having slightly different pitch (two semitones apart) are alternated. Which of these two was more audible when the noise was still playing, the lower-pitched one or the higher-pitched one? They differ not only in their pitch, but also in their interaural phase.

In this instance the low-pitched tone is presented antiphasically, which improves its audibility for most listeners. The higher-pitched tone is less audible because it is presented in-phase, preventing the use of binaural information for its detection.

It is also instructive to listen to this demo monaurally by lifting one earphone and letting it rest e.g. on the temple of the head, while listening to the other earphone: the binaural effect, here the unmasking of the antiphasic tone, should then disappear. When listening monaurally over the other ear, the tones should still be inaudible. This shows that binaural detection is really “listening between the ears.” That is, with both ears you can hear things unheard of by either ear alone.

Supplemental audio from the 2019 review by Philip X. Joris and Marcel van der Heijden, "Early Binaural Hearing: The Comparison of Temporal Differences at the Two Ears," from the Annual Review of Neuroscience: https://www.annualreviews.org/doi/10.1146/annurev-neuro-080317-061925?utm_source=soundcloud&utm_medium=ne.joris&utm_campaign=suppvideo

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