Modeling the Influence of Bandwidth and Envelope on Categorical Loudness Scaling

Area of Science:

• Auditory Neuroscience
• Psychoacoustics
• Signal Processing

Background:

• Previous studies observed loudness reduction in five-tone complexes with bandwidths less than one-half octave.
• This phenomenon was noted at 60 dB Sound Pressure Level (SPL) centered at 1 kHz.

Purpose of the Study:

• To investigate the loudness reduction phenomenon in band-limited noise across various frequencies and sound levels.
• To simulate these loudness judgments using a Neural Ensemble Averaging (NEA) model, modeling central auditory processing.

Main Methods:

• Measured multi-frequency equal-loudness contours (ELC) using a categorical loudness scaling (CLS) paradigm in 100 adults with normal to moderate hearing loss.
• Employed a Bayesian adaptive algorithm for efficient ELC estimation across pure-tone, quarter-octave noise, and octave noise conditions.
• Simulated loudness judgments using a NEA model incorporating a nonlinear cochlear model and neural spike generation.

Main Results:

• Mid-bandwidth loudness reduction was most pronounced at moderate sound levels and frequencies around 1 kHz.
• The NEA model successfully approximated this loudness reduction feature.
• The findings suggest that early stages of the central auditory system play a role in loudness perception.

Conclusions:

• The study confirms and extends the observation of loudness reduction in band-limited sounds.
• The NEA model provides a valuable tool for understanding the neural basis of loudness perception.
• Evidence points to the involvement of early central auditory processing in loudness judgments.