Exploring frequency modulation features and resolution in the modulation spectrum

Modulation frequency features have shown promise in representing distinguishing characteristics of audio signals. The modulation spectrum, which is described as an acoustic frequency versus modulation frequency representation of a signal, was developed to further explore this type of signal analysis and filtering. Previous research employing the modulation spectrum has focused on its representation of amplitude modulation (AM) characteristics in a signal, but little focus has been placed on the observance of frequency modulation (FM) structure in the modulation spectrum. We explore parameters that affect the resolution of the modulation spectrum and, thus, describe how both AM and FM spectral features may be observed. We also suggest why such modulation spectral features from the modulation spectrum may be useful for audio data mining tasks. We hope this emphasis on resolution and representation of simple AM/FM spectral features may lead to deeper intuition about this modulation spectrum and wider application.