Interactions Between Digital Noise Reduction and Reverberation: Acoustic and Behavioral Effects

Area of Science:

• Audiology
• Acoustics
• Signal Processing

Background:

• Digital noise reduction (DNR) is crucial for hearing aid users to improve speech perception in noisy environments.
• The effectiveness of DNR under reverberant conditions, where sound quality is further degraded, remains largely unknown.

Purpose of the Study:

• To investigate the acoustic and perceptual impacts of DNR processing on speech-in-noise for individuals with hearing impairment.
• To evaluate DNR performance across a spectrum of reverberant environments.

Main Methods:

• An experimental design was employed to simulate various reverberation levels, including an anechoic control.
• Speech-in-noise stimuli with different signal-to-noise ratios (SNRs) were processed using spectral subtraction DNR.
• Acoustic analysis quantified SNR improvement, while perceptual assessments measured speech intelligibility, listening effort, speech naturalness, and noise comfort.

Main Results:

• SNR improvement from DNR diminished with increasing reverberation.
• DNR significantly reduced speech intelligibility in all reverberant conditions, unlike in the anechoic control.
• Subjective feedback indicated increased listening effort and reduced speech naturalness with DNR in reverberant settings.

Conclusions:

• Reverberation negatively impacts spectral subtraction DNR algorithms, impairing noise reduction and distorting speech.
• DNR may be most beneficial in low-reverberation environments; its use in highly reverberant settings could be detrimental.
• Further research with commercial hearing aids in realistic reverberant conditions is recommended.