Quantifying the distortion products generated by amplitude-modulated noise.

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal processing

Background:

• Sinusoidal amplitude modulation (SAM) of carriers can produce audible distortion products near the modulation frequency.
• These distortion products complicate the use of bandpass-filtered SAM noise in temporal processing research.
• Existing methods often mask distortion using unmodulated noise, but the nature of the distortion itself requires clarification.

Purpose of the Study:

• To investigate the characteristics of distortion products generated by bandpass noise carriers in SAM stimuli.
• To clarify the form of distortion and its perceptual relevance, particularly the distortion tone at the modulation frequency.
• To assess the impact of distortion tone cancellation on auditory performance in temporal processing tasks.

Main Methods:

• Measurement of the level and phase of the distortion tone using two experimental paradigms.
• Assessment of modulation-frequency difference limens for filtered SAM noise, with and without distortion tone cancellation.
• Measurement of masked thresholds for unmodulated noise bands to investigate quadratic distortion.

Main Results:

• The distortion products include two distortion-noise bands and a distortion tone at the modulation frequency.
• Auditory performance significantly deteriorates when the distortion tone is canceled during modulation-frequency discrimination tasks.
• Unmodulated noise also produces quadratic distortion, potentially explaining phenomena like remote masking.

Conclusions:

• The distortion tone generated by SAM noise plays a crucial role in auditory perception and temporal processing.
• Understanding and characterizing these distortion products is essential for accurate psychoacoustic research.
• Quadratic distortion from unmodulated noise should be considered in auditory masking studies.