Perception of internally generated noise in hearing amplification

Area of Science:

• Audiology
• Acoustics
• Hearing Science

Background:

• Internal noise in hearing aid amplifiers can impair speech understanding.
• Determining audible and objectionable noise levels is crucial for hearing aid specification and fitting.

Purpose of the Study:

• To determine the perceived audible and objectionable levels of internal hearing aid amplifier noise.
• To compare noise perception between individuals with hearing loss and normal hearing.
• To investigate the relationship between noise levels, audiometric configuration, and noise perception.

Main Methods:

• Eight subjects with moderate hearing loss and five normal-hearing subjects were tested.
• A test amplifier without acoustic input was used to generate internal noise.
• Two noise types were simulated: output stage noise and input stage noise shaped by the National Acoustics Laboratory-Revised (NAL-R) response.

Main Results:

• The perceived audible and objectionable noise levels were recorded for each subject.
• Overall noise levels and spectra were analyzed for both noise types.
• A correlation was found between 1/3-octave noise measurements, audiometric configuration, and the audibility of internal noise.

Conclusions:

• Internal amplifier noise audibility can be predicted based on audiometric configuration and 1/3-octave noise measurements.
• Simulated input-stage and output-stage noise yielded similar audibility thresholds.
• Findings support improved hearing aid fitting by considering internal noise perception.