Periodicity Pitch Detection in Complex Harmonies on EEG Timeline Data

TL;DR

This study investigates how the human brain perceives periodicity pitches of complex musical harmonies using EEG data and Fourier analysis, revealing that the brain adds these pitches during auditory processing despite their absence in the stimulus.

Contribution

It introduces a method to detect periodicity pitches in EEG responses to complex harmonies, highlighting neural processing of missing fundamentals during hearing.

Findings

Periodicities are detected with some accuracy in EEG spectra.

Jitter affects the precision of periodicity pitch detection.

Brain adds missing fundamental frequencies during auditory perception.

Abstract

An acoustic stimulus, e.g., a musical harmony, is transformed in a highly non-linear way during the hearing process in ear and brain. We study this by comparing the frequency spectrum of an input stimulus and its response spectrum in the auditory processing stream using the frequency following response (FFR). Using electroencephalography (EEG), we investigate whether the periodicity pitches of complex harmonies (which are related to their missing fundamentals) are added in the auditory brainstem by analyzing the FFR. While other experiments focus on common musical harmonies like the major and the minor triad and dyads, we also consider the suspended chord. The suspended chord causes tension foreign to the common triads and therefore holds a special role among the triads. While watching a muted nature documentary, the participants hear synthesized classic piano triads and single tones with a duration of 300ms for the stimulus and 100ms interstimulus interval. We acquired EEG data of 64 electrodes with a sampling rate of 5kHz to get a detailed enough resolution of the perception process in the human brain. Applying a fast Fourier transformation (FFT) on the EEG response, starting 50ms after stimulus onset, the evaluation of the frequency spectra shows that the periodicity pitch frequencies calculated beforehand +/-3Hz occur with some accuracy. However, jitter turned out as a problem here. Note that the sought-for periodicity pitch frequencies do not physically exist in the frequency spectra of the stimuli.