The auditory steady-state response (ASSR) can be thought of as an electrophysiologic response to rapid auditory stimuli. The goal of ASSR is to create an estimated audiogram from which questions regarding hearing, hearing loss, and aural rehabilitation can be answered.
Uncover what auditory steady-state response (ASSR) is, how it works, and the potential benefits it holds. Learn more through our comprehensive resources and advice on ASSR testing & interpretation, as well as related topics on the science of sound
The auditory steady-state response (ASSR) can be thought of as an electrophysiologic response to rapid auditory stimuli. The goal of ASSR is to create an estimated audiogram from which questions regarding hearing, hearing loss, and aural rehabilitation can be answered. ASSR allows the hearing care professional to create statistically valid audiograms for those unable or unwilling to participate in traditional behavioral tests. ASSR relies on statistical measures to determine if and when a threshold is present. ASSR design and functionality vary across manufacturers.
Unlike auditory brainstem response (ABR) which looks at amplitude and latency of the response in the time domain, ASSR looks at amplitudes and phases in the frequency domain. Responses are detected using a statistic-based mathematical detection algorithm to determine if a response is present or not. Another difference is that while it is only possible to test one frequency per ear at a time in frequency-specific threshold ABR. ASSR allows for binaural testing; four frequencies in each ear at the same time (eight simultaneous presentations).
The ASSR technology is completely objective and based on statistical probability rather than subjective assessment of response waveforms. The most important audiological application of ASSR is to provide an estimate of the pure tone audiogram, which is used for rehabilitation purposes.
Patient preparation is very important. The electrode sites must be prepared and cleaned in order to obtain acceptably low skin impedance. It is recommended to have impedance values below 3k or lower. The same electrode placement for ASSR is also used for ABR allowing for easy switching between the test types.
ASSR and ABR have important differences, too. Rather than depending on amplitude and latency, ASSR uses amplitudes and phases in the spectral (frequency) domain. ASSR depends on peak detection across a spectrum, rather than peak detection across a time versus amplitude waveform (see John and Picton1). ASSR Test is evoked using repeated sound stimuli presented at a high repetition rate, whereas ABR is evoked using brief sounds presented at a relatively low repetition rate.
ABR recordings are most often dependent on the examiner subjectively reviewing the waveforms and deciding whether a response is present. Determining the response becomes increasingly difficult as the ABR approaches true threshold—which is when the decision (response or no response) is most important. ASSR Test uses an objective, sophisticated, statistics-based mathematical detection algorithm to detect and define hearing thresholds.
ABR protocols typically use clicks or tone-bursts in one ear at a time. ASSR Test can be used binaurally, while evaluating broad bands or four frequencies (500 Hz, 1,000 Hz, 2,000 Hz, and 4,000 Hz) simultaneously.
ABR is useful in estimating hearing thresholds essentially from 1,000 Hz to 4,000 Hz, in typical (non-ski-slope) mild-moderate-severe hearing losses. ASSR Test can also estimate hearing thresholds across the same range as the ABR, but ASSR Test offers more spectral information more quickly, and can estimate and differentiate hearing within the severe-to-profound hearing loss ranges.
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