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Real ear measures of auditory brain stem response click spectra in infants and adults
1University of Kansas Medical Center, Kansas City.
Insights
Infant and adult ears resonate auditory brain stem response (ABR) click stimuli differently, with infants showing higher, more variable spectral peaks. This highlights the need for infant-specific ABR norms in hearing assessments.
Area of Science:
- Audiology
- Neuroscience
- Bioacoustics
Background:
- Auditory Brainstem Response (ABR) testing is crucial for infant hearing screening.
- Understanding acoustic properties of the ear canal is vital for accurate ABR interpretation.
- Previous research has not fully detailed spectral differences in ABR click stimuli between infant and adult ears.
Purpose of the Study:
- To investigate and compare the spectral characteristics of auditory brain stem response (ABR) click stimuli in infant and adult ear canals.
- To determine if differences in spectral resonance necessitate distinct normative data for infant ABR testing.
Main Methods:
- Utilized insert earphones to deliver click stimuli (30 and 60 dB nHL) to 11 infants and 15 adults.
- Employed an ER-7C probe microphone and spectrum analyzer to measure spectral content within the ear canals.
- Analyzed spectral peaks and variability between the two age groups.
Main Results:
- Infant ear canals exhibited higher mean spectral peak frequencies (2339.77 Hz) compared to adults (1618.75 Hz).
- Infants demonstrated significantly greater variability in spectral peaks (SD = 669.37) than adults (SD = 319.0).
- The total energy of the click stimuli remained consistent across both age groups.
Conclusions:
- Click stimuli used in ABR testing resonate differently in infant versus adult ear canals.
- Infant ear canal resonance is more variable, supporting the necessity of age-specific ABR normative data.
- Findings suggest infant ABRs may correlate more strongly with high-frequency hearing thresholds.
Abstract:
This study investigated spectral differences for auditory brain stem response (ABR) clicks measured in infant and adult ear canals. Click stimuli were presented via insert earphones into the ear canals of 15 adults and 11 infants at 30 and 60 dB nHL. An ER-7C probe microphone fed the stimulus to a spectrum analyzer for analysis of spectral content. Infants had spectral peaks at higher frequencies (mean = 2339.77 Hz) than adults (mean = 1618.75 Hz). The infants also exhibited greater variability in their spectral peaks (SD = 669.37) than did adults (SD = 319.0). The total energy of the clicks was the same in infants' and adults' ears. These results indicate that click stimuli such as those used for ABR testing resonate in infant and adult ears differently, and that the resonance in infants is much more variable than the resonance of adults. These findings provide additional evidence for the need to use infant norms when screening infant hearing using the ABR. Similarly, the findings suggest that infant ABRs may be more correlated with higher frequency behavioral thresholds than those assumed for adults.