AAA 2018 Presentation – Improving Signal-To-Noise Ratio for Optimizing Repeatable ABR
Visit us at AAA 2018 – Vivosonic Booth #1425!
Join us for an education session:
EC209: Improving Signal-To-Noise Ratio for Optimizing Repeatable Auditory Brainstem Responses
Thursday, April 19, 2018: 11:30 AM-12:30 PM
Room: 205ABC
Aaron Steinman, PhD, PEng – Director of Research, Vivosonic Inc. (Lead Presenter)
Instructional Level
- Intermediate
Learning Objectives
- Upon completion, participants will be able to identify the importance of SNR in ABR and how the contribution of both signal enhancement and noise reduction contributes to improved ABR response morphology and hence detection.
- Upon completion, participants will be able to assess the clinical significance of different noise reduction strategies for improving SNR and confirming the repeatability of ABR waveforms.
- Upon completion, participants will be able to identify the value of alternate stimuli to improve the signal component of the SNR in coordination with noise reduction strategies.
Session Category
Electro/physiology (E)
Abstract
The signal-to-noise ratio (SNR) is critical in determining the presence and absence of a small response, such as the ABR. A superior SNR results from the combination of both noise reduction and signal improvement strategies. Research indicates that noise reduction has greater effect on SNR than improving signal. Without appropriate noise reduction, improved signal response may not be relevant. Combining innovative noise-reducing hardware and algorithm with novel chirp stimuli offers a potent strategy for optimizing repeatable ABR response generation.
Summary
The signal-to-noise ratio (SNR) is very important in determining the presence and absence of a small response, such as the ABR. Theoretical simulations indicate a 20% reduction in noise corresponds to a 25% improvement in SNR. When compared to an equal change in signal improvements, noise reduction has a stronger contribution to enhanced SNR.
There are two types of noise reduction strategies: hardware, where emphasis is to prevent noise from contaminating the signal; and algorithm, where emphasis is to remove noise that has contaminated the signal. Hardware noise reduction strategies include: shielded wires, filtering before amplification, tuned filters to the ABR frequency band, amplification before electrical and magnetic noise introduction, and battery operated to reduce noise from the mains. Noise reduction algorithms include artifact rejection (where entire responses are deemed to be too noisy and removed), averaging (where the random noise eventually is reduced), Kalman-weighted averaging (where the weighting is based on its noise content), intelligent buffering (where the noise is distributed between two concurrent, but statistically independent waveforms, allowing for realistic, real-time repeatability and noise evaluation), SNR optimized adaptive processing (SOAP) (where the primary dominant harmonic noise is proactively removed from the averaged response), and SOAP-plus (where the secondary and tertiary dominant harmonic noise is proactively removed from the averaged response, in addition to the primary dominant harmonic noise of SOAP).
With respect to signal improvement, much has already been said about the effectiveness of both broadband and narrow-band chirp relative to standard click and toneburst stimuli to improve the signal amplitude of the response. However, it is important to recognize that the response to the non-traditional stimuli are different – both in frequency content and expected latencies. As such, there is an important caveat: new stimuli need appropriate clinical research to establish equivalence with the universally accepted stimuli (clicks and tonebursts) as well as normative data for normal hearing and hearing impaired populations.
A superior SNR results from the combination of both noise reduction and signal improvement strategies. However, without appropriate noise reduction, improved signal response may not be relevant. Clinical results supporting these SNR improvement strategies will be presented and the impact on the resultant ABR waveform will be discussed.
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