The ear lacks the eye’s directional receptors, relying on canal analysis

Evidence

This is a very small delay but a variation from this to zero determines the direction of sounds at low frequencies. Figure 2.25 shows how this delay varies as a function of angle, where positive delay corresponds to a source at the right of the median plane and negative delay corresponds to a source on the left. Note that there is no difference in the delay between front and back positions at the same angle. This means that we must use different mechanisms and strategies to differentiate between front and back sounds. There is also a frequency limit to the way in which sound direc­ tion can be resolved by the ear in this way. This is due to the fact that the ear appears to use the phase shift in the wave caused by the interaural time difference to resolve the direction; that is, the ear measures the phase shift given by: where the phase difference between the ears in radia ITD Φ  ( ns and the frequency in Hz When this phase shift is greater than  radians (180°) there will be an unre­ solvable ambiguity in the direction because there are two possible angles- one to the left and one to the right-that could cause such a phase shift. — David Howard, Jamie Angus, coustics and Psychoacoustics, 712 (#expands, via linked claim)

However, although the time domain waveform is radically different the fre­ quency domain is very similar, as the amplitudes are identical—only the phase of some of the harmonics has changed. … Interestingly, in many cases, the resulting wave is perceived as sounding the same, even though the waveform is different. This is because the ear, as we will see later, appears to be less sensitive to the phase of the individual fre­ quency compared with the relative amplitudes. However, if the phase changes are extreme enough we can hear a difference (see Schroeder, 1975). — David Howard, Jamie Angus, coustics and Psychoacoustics, 451 (#corroborates, via linked claim)

Categorization

• XREF: connects to: The ear resolves low-frequency direction by measuring phase shift — David Howard, Jamie Angus, coustics and Psychoacoustics, 712; The human ear is largely insensitive to signal phase — David Howard, Jamie Angus, coustics and Psychoacoustics, 451; Unlike the eye, the ear has no primary directional sensitivity — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1510

Broader Connections

• The ear resolves low-frequency direction by measuring phase shift #expands (0.82) — David Howard, Jamie Angus, coustics and Psychoacoustics, 712
• The human ear is largely insensitive to signal phase #corroborates (0.78) — David Howard, Jamie Angus, coustics and Psychoacoustics, 451