Speech-Like ASSR Stimuli for Hearing Aid Fitting Verification
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Solution Overview
Problem
Current methods for recording Auditory Steady State Responses (ASSR) face challenges in accurately verifying hearing aid fitting, especially in infants and individuals with severe mental or physical impairments, due to unreliable behavioral measures and interference from background noise, as well as the limitations of existing auditory evoked potential techniques like ABR and CAEP.
Innovation Solution
A new technique that modifies ASSR stimuli to be more speech-like by incorporating amplitude variations over time, similar to free-running speech, while maintaining the predictable frequency domain structure, allowing for improved detection and processing by hearing aids, and objective assessment of auditory system functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional transient acoustic stimuli are presented at slow repetition rates to obtain classical AEPs, then response resolution is improved, but measurement time increases and productivity decreases
Solution Approach 1:
The patent employs periodic amplitude modulation of pure tones at specific repetition rates (e.g., 80 Hz, 100 Hz, 200 Hz) to elicit steady-state responses. This periodic stimulation allows the auditory system to generate synchronized neural responses that can be detected using frequency domain analysis (FFT), enabling rapid assessment within seconds rather than requiring slow transient stimulation over extended periods.
Solution Approach 2:
The patent replaces time-domain analysis of transient responses with frequency-domain analysis of steady-state responses. By transforming the detection approach from temporal to spectral domain (using FFT to identify response frequencies matching stimulus modulation rates), the system achieves both high precision and rapid measurement, resolving the contradiction between response resolution and measurement time.
2Measurement precision
If sinusoidally amplitude modulated pure tones are used to evoke ASSR, then frequency-specific stimulation is achieved, but response amplitude remains small due to limited auditory nerve fiber recruitment
Solution Approach 1:
The patent modifies the modulation depth parameter of the amplitude-modulated tones to optimize the balance between frequency-specificity and response amplitude. By adjusting modulation depth within specific ranges (e.g., 20-80%), the system enhances neural synchronization and response amplitude while maintaining the frequency-specific stimulation characteristics, thereby resolving the contradiction between precise frequency targeting and sufficient response magnitude for reliable detection.
3Productivity
If multiple frequency-specific stimuli are presented simultaneously to enable parallel ASSR recording, then productivity increases, but response detection becomes more difficult due to overlapping signals
Solution Approach 1:
The patent segments the auditory frequency spectrum into distinct bands (e.g., 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, 4000 Hz) and presents amplitude-modulated tones at each frequency with unique modulation rates. This segmentation allows simultaneous stimulation of multiple frequency regions while maintaining distinguishable response signatures in the frequency domain, enabling parallel recording without signal overlap confusion.
Solution Approach 2:
The patent adds the frequency dimension as an additional degree of freedom for signal separation. By assigning each stimulus frequency a distinct modulation rate and detecting responses at corresponding frequencies in the spectral domain, the system can simultaneously record ASSR from multiple frequency-specific stimuli without interference, transforming the detection problem from temporal to spectral dimension.
4Ease of operation
If behavioral measures are used for hearing assessment in infants and individuals with severe impairments, then subjective feedback is obtained, but reliability decreases due to attention and arousal variability
Solution Approach 1:
The patent employs objective physiological measures (ASSR recorded via EEG) that do not require active participation, attention, or behavioral responses from the subject. The auditory system itself generates the measurement signal through synchronized neural responses to amplitude-modulated stimuli, eliminating the need for subject cooperation or behavioral feedback, thereby ensuring reliable assessment in infants and individuals with severe impairments.
Data Source
AI summary
A diagnostic system for recording auditory steady-state responses of a person comprises a) a stimulation unit for providing an acoustic stimulus signal to an ear of the person, and b) a recording unit for recording the auditory steady-state responses of the person origination from said acoustic stimulus signal, wherein the stimulation unit is configured to provide that the acoustic stimulus signal comprises a speech-like stimulus provided as a combination of a series of individual frequency-specific stimuli, each having a specified, e.g. predetermined, frequency bandwidth, presentation rate, amplitude and amplitude-modulation. The application further relates to a combined system comprising a diagnostic system and a hearing aid. The invention may e.g. be used for diagnostic instruments for verifying the fitting of a hearing aid.