Summary of: Lightfoot, G., Cairns, A., & Stevens, J. (2010). Noise levels required to mask stimuli used in auditory brainstem response testing. International journal of audiology, 49(10), 794–798. https://doi.org/10.3109/14992021003796895
Masking the non-test ear is necessary for certain audiometric configurations to ensure that the ABR recording accurately reflects the response (or lack of) of the test ear. However, data is limited in regards to the required level of masking noise necessary in ABR tests. This study attempts to quantify the relative masking level (RLM) in 22 normal-hearing adults for clicks and tone pips common to ABR tests via TDH-39 headphones and insert earphones. Results show that RLM is 4.5 dB greater when the noise level is increased from below the stimulus relative to when the noise is decreased from above the stimulus. Overall, RLMs are as much as 30 dB SPL at 500 Hz and 25 dB SPL across the frequencies of 1000, 2000 and 4000 Hz. RLMs approach 27 dB SPL for clicks. Therefore, a value of 30 dB above the stimulus is recommended for ensuring effective masking of the ABR stimulus in the same ear. The authors value is recommended when calculating the level of noise necessary to prevent cross-hearing during ABR testing and this is used in the NHSP masking calculator.
Related course: Beyond the Basics: Threshold ABR