Fig 1.
Schema of the tones for the right ear test.
The fundamental component of (B_R) is higher in frequency than that of (A_R). The highest component of (B_R) is lower in frequency than that of (A_R). Tones (C_R) and (D_R) are identical to (A_R) and (B_R), respectively, except both (C_R) and (D_R) contain one higher component of equal frequency. Arrows indicate the differences in frequencies between the tones.
Fig 2.
Schema of the tones for the left ear test.
The tones for the left ear test are named (A_L), (B_L), (C_L), and (D_L). These are complex or pure tones whose components of less than 900 Hz were eliminated, in addition to the tones of the right channel.
Fig 3.
Illustration briefly describing the second experiment.
Subjects were asked whether they had heard the sequence of the tones in the left ear at the same pitches or at different pitches compared to those in the right ear. Before obtaining the response, this illustration was shown to them for a better comprehension of the task.
Fig 4.
Results of the first experiment for the right ear test.
When complex tones (A_R) and (B_R) were compared in the right ear, most subjects judged (B_R) as higher in pitch. Similar results were obtained in the additional experiment in which complex tones (C_R) and (D_R) were used. Most subjects judged (D_R) to be higher in pitch. *: subjects showed ambiguous results.
Fig 5.
Results of the first experiment for the left ear test.
In the left ear, which simulated low-tone hearing loss, (A_L) or (C_L) was judged higher in pitch by most subjects (Fisher's exact probability test, p < 0.01). There was one subject that judged (D_L) as higher in pitch than (C_L). *: subjects showed ambiguous results.
Fig 6.
Results of the second experiment.
The results of the second experiment in which subjects heard the sequence of tones in both ears simultaneously. (1) When they heard the tones (A_R) plus (A_L), followed by (B_R) plus (B_L), approximately half of the subjects heard the sequence of the tones in the left ear at different pitches from that in the right ear. (2) When they heard the tones (C_R) plus (C_L), followed by (D_R) plus (D_L), the results were similar to those of (1).