Multiplicative effects on sentence comprehension for combined acoustic distortions

Area of Science:

• Audiology
• Speech Science
• Signal Processing

Background:

• Speech comprehension is crucial for communication.
• Understanding how signal distortions affect speech perception is vital for audiological applications.
• Previous research has examined individual distortions, but combined effects require further investigation.

Purpose of the Study:

• To investigate the impact of combining low-pass (LP) filtering with time compression, interruption, and noise masking on speech comprehension.
• To determine if the effects of combined distortions are additive or multiplicative.
• To explore the utility of LP filtering in simulating high-frequency hearing loss effects.

Main Methods:

• Normal-hearing young men completed multiple-choice tests on distorted colloquial sentences.
• Distortions included LP filtering (1-4 kHz), time compression (250 wpm), interruption (50ms on/off), and speech-spectrum noise masking (+2 dB S/N).
• All 12 combinations of LP filtering with other distortions were tested, with individual conditions adjusted for ~90% accuracy.

Main Results:

• LP filtering above 1 kHz alone caused minimal comprehension reduction (5-10%).
• Combined distortions showed significantly greater comprehension reduction than additive effects.
• LP filtering above 2 kHz, combined with noise masking, reduced performance from 89.4% to 59.7%.

Conclusions:

• Simultaneous signal distortions have a compounded, non-additive effect on speech comprehension.
• LP filtering can effectively simulate the impact of high-frequency hearing loss in combination with other distortions.
• These findings validate the complex nature of auditory distortion interactions.