Audibility of partials in inharmonic complex tones

Area of Science:

• Auditory perception
• Psychoacoustics
• Music cognition

Background:

• Complex tones are composed of multiple frequency components called partials.
• The auditory system's ability to resolve these partials is crucial for sound perception.
• Individual differences in auditory filter bandwidth can affect partials perception.

Purpose of the Study:

• To investigate how the spacing of partials in complex tones, relative to auditory filter bandwidth, affects the ability to discern individual partials.
• To explore the influence of component frequency and auditory filter characteristics on partials perception.

Main Methods:

• Musically trained subjects listened to complex tones with varying partial spacings (0.75 to 2 ERB).
• Subjects performed a frequency discrimination task, identifying if a mistuned probe tone was higher or lower than a complex tone partial.
• Auditory filter shapes were measured using the notched noise method.

Main Results:

• High accuracy (>90%) for outer partials when spacing exceeded 1 ERB; performance decreased at 0.75-1.0 ERB.
• Inner component perception improved with increased ERB spacing from 1 to 2.
• Irregularities and errors observed for spacings ≤1.25 ERB, potentially linked to middle ear function.
• Poorer performance for higher frequency inner components (>1000 Hz) suggested by phase-locking deterioration.
• Broader auditory filters correlated with greater difficulty in resolving partials.

Conclusions:

• Auditory filter bandwidth and component spacing are critical for resolving partials in complex tones.
• Middle ear transfer function irregularities and neural phase-locking precision may explain observed performance variations.
• Individual differences in auditory filter width significantly impact the ability to hear out individual partials.