Hearing impairment often leads to decrease in auditory sensitivity or hearing dysfunction. Auditory brainstem response (ABR) is an objective method to detect hearing loss.  

ABR induced by click is generally considered as the gold standard; however, it has some limitations that may cause distortion and attenuation of acquired ABR waveform.  

A research group led by Prof. CHEN Shixiong from the Shenzhen Institutes of Advanced Technology (SIAT) of the Chinese Academy of Sciences proposed a swept-tone-based stimulus and a random stimulation method to solve these problems. Their study was published in Frontiers in Human Neuroscience.  

The researchers designed swept-tone stimulus to reconstruct the arrival time of different frequency components with respect to the delay characteristics of cochlear basement membrane. They compared the performance of the proposed swept-tone-induced ABR and the click-induced ABR at different test levels and different stimulus rates.  

The results showed that the waveform morphology of swept-tone-induced ABR was better than that of click-induced ABR across different test levels and stimulus rates.  

Moreover, comparing with the click-induced ABR at different sweeps, they found that the proposed swept-tone-induced ABR effectively induced the ABR waveform at a relatively faster rate.  

In order to further improve the efficiency of swept-tone based ABR, a random stimulation rate (RSR) method was proposed by introducing a random interval between two adjacent stimuli, which made the unwanted part no longer synchronized with the stimulus onset. These undesired parts canceled each other out after applying averaging technique.  

The researchers found that the proposed RSR method was consistently repeatable and reliable in multiple trials of repeated measurements. The ABR waveforms of the RSR method showed better Wave I-V morphology across different stimulation rates and stimulus levels.  

The correlation coefficients as functions of averaging time showed that the ABR waveform of the RSR method stabilized faster and therefore it could be used to speed up current ABR measurements with more reliable testing results.  

"These two methods can avoid the attenuation and distortion of ABR signals from different aspects. The future direction can be the combination of these two methods to further investigate their performance on clinical hearing detection technique," said Prof. CHEN.  

The proposed swept-tone approach and RSR method can provide new solutions to improve the sensitivity of ABR detection and aid the adequate reconstruction of ABR signals towards a more effective means of hearing loss screening, brain function diagnoses and potential brain-computer interface.