Spectral and level effects in noise-on-tone suppression

Area of Science:

• Auditory perception
• Psychoacoustics
• Signal processing in hearing

Background:

• Understanding the internal representation of sound is crucial for auditory research.
• Masking is a phenomenon where one sound obscures another, impacting auditory perception.
• Spectral notches in noise can influence the perception of tones.

Purpose of the Study:

• To investigate the 'unmasking' effect of noise with spectral notches on the effective internal level of a masker tone.
• To quantify how noise characteristics (level, notch width, shape) influence auditory suppression.

Main Methods:

• Measured forward masking of a 1-kHz tone using a masker tone at the same frequency and intensity (50 dB SPL).
• Introduced noise with varying spectral notch widths and levels, centered or offset from the masker tone.
• Assessed changes in signal threshold to infer the effective internal level of the masker tone.

Main Results:

• Noise with a spectral notch significantly reduced the effective internal level of the masker tone, by up to 30 dB.
• The unmasking effect was strongest for narrow notches (250 Hz) and diminished as notch width increased.
• Noise components adjacent to the masker tone were most effective in suppressing its internal level.

Conclusions:

• Auditory suppression, induced by noise components within a spectral notch, can substantially reduce the perceived level of a target tone.
• The frequency selectivity of auditory processing plays a key role in mediating this suppression effect.
• These findings contribute to understanding how the auditory system processes complex sound environments.