Narrow noise band detection in a complex masker: masking level difference due to harmonicity

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal processing

Background:

• Complex tones are composed of multiple frequency components called partials.
• The harmonicity of these partials influences how listeners perceive sounds.
• Previous theories suggested envelope modulation from unresolved partials caused masking level differences.

Purpose of the Study:

• To investigate the role of inharmonicity in auditory masking.
• To determine the underlying mechanism of the masking level difference due to harmonicity (HMLD).
• To explore the influence of partial mistuning on sound detection.

Main Methods:

• Listeners detected a narrow band of noise masked by random-phase complex tones.
• Inharmonicity was introduced by mistuning partial frequencies from a fundamental frequency (F0).
• Masked detection thresholds were measured across different center frequencies and mistuning extents.

Main Results:

• Masked detection thresholds were lower for harmonic maskers compared to inharmonic ones (0.5-2.5 kHz).
• The HMLD was present for resolved partials and decreased with increasing center frequency.
• Significant disruption of HMLD occurred with mistunings beyond 12% of F0, while smaller mistunings yielded similar thresholds to harmonic maskers.

Conclusions:

• The findings do not support envelope modulation by unresolved partials as the primary cause of HMLD.
• Neighboring partials' harmonicity significantly influenced HMLD more than distant ones.
• A mechanism of harmonic cancellation provides the best explanation for the observed HMLDs.