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. Author manuscript; available in PMC: 2017 Apr 1.
Published in final edited form as: Neuroimage. 2016 Jan 28;129:401–413. doi: 10.1016/j.neuroimage.2016.01.050

Figure 1. Illustration of Cochlear and Earphone Distortion Products.

Figure 1

A. Examples of distortion products (orange points) resulting from nonlinearities in the cochlea’s response to sound. The sound stimulus contained energy only at harmonics 10–20 of a 100 Hz F0 (black points), but audible DPs were generated at many lower harmonics. DPs were measured psychophysically using the beat-cancellation technique in two subjects, and the pulsation-threshold method in one subject (see Methods). Pure-tone audibility thresholds are plotted for comparison. Error-bars for the beat-cancellation measurements indicate the range of cancellation-tone levels that removed audible beating. B. Examples of distortion products resulting from earphone nonlinearities. Each figure plots the spectrum of the audio waveform produced by an earphone for a stimulus composed of harmonics 10–20 of a 200 Hz F0. Sensimetrics earphones, commonly used in auditory neuroimaging, produced audible DPs at frequencies not in the original stimulus. STAX earphones produced no measurable DPs for the same stimulus.