Effects of degree and symmetricity of bilateral spectral smearing, carrier frequency, and subject sex on amplitude of evoked auditory steady-state response signal

Abstract

The characteristics of an auditory steady-state response (ASSR) signal can be affected by the pathophysiological statuses of the left and right ears, such as a smeared sensation by native spectral smearing owing to sensorineural hearing impairment, because they can affect the perception of the stimulus, the degree of concentration on the stimulus and comfort in concentration. However, to date, few studies have examined the effects of such smeared sensations on the amplitude of the evoked ASSR signal. In this study, we synthesized various auditory stimuli with different degrees of spectral smearing using a hearing loss simulator to match the age of participant groups with different degrees of spectral smearing. We then performed three subjective tests, representing symmetric and asymmetric bilateral spectral smearing, with 16 normal-hearing individuals to observe the effects of the severity and symmetricity of bilateral spectral smearing, the value of the carrier frequency of auditory stimuli, and the sex of the individual on the amplitude in evoked ASSR signals. The experimental results demonstrated the following: (1) the application of spectral smearing to normal sounds may result in amplitude-reduced ASSR signals, (2) the effect of spectral smearing on the amplitude of the ASSR signals is most significant when the degrees of bilateral spectral smearing are asymmetric, (3) the selection of carrier frequency in an auditory stimulus can affect the amplitude of evoked ASSR signals regardless of the degree of spectral smearing, and (4) the sex of the individual can affect the amplitude of the evoked ASSR signal in various test conditions. The results of this study can help estimate the effects of smeared sensation by spectral smearing owing to sensorineural hearing impairment on the amplitude of evoked ASSR signals.

Keywords: Augmentative and alternative communication; Central auditory processing; Electrophysiology; Hearing loss.

Fig. 1

Results of simulator evaluation test for hearing threshold setup (output patterns of simulator vs. white noise input). a Applied linear audiograms for ML, MSL and SL setups, b ML setup, c MSL setup, d SL setup. ML moderate hearing loss, MSL moderately-severe hearing loss, SL severe hearing loss

Fig. 2

Time-domain waveforms of spectral smearing-reflected auditory stimuli. a S₅₀₀{37}_NH/ML/MSL/SL, b S₂₀₀₀{43}_NH/ML/MSL/SL

Fig. 3

Results of SYM-I test (mean and standard deviation). HI represents average of ML, MSL and SL setups. a Entire group (overall 16 individuals), b female group (eight individuals), c male group (eight individuals)

Fig. 4

Results of SYM-II test (mean and standard deviation). a Entire group, b female group, c male group

Fig. 5

Results of ASYM test (mean and standard deviation). In figures, NH/NH and ML/ML represent results of SYM-II test (equivalent to NH and ML in Fig. 4). a Entire group, b female group, c male group