The Audible Contrast Threshold (ACT™) test: a clinical spectro-temporal modulation detection test

Over the last decade, multiple studies have shown that hearing-impaired listeners’ speech-in-noise reception ability, measured with audibility compensation, is closely associated with performance in spectro-temporal modulation (STM) detection tests. STM tests thus have the potential to provide highly relevant beyond-the-audiogram information in the clinic, but the available STM tests have not been optimized for clinical use in terms of test duration, required equipment, and procedural standardization. The present study introduces a quick-and-simple clinically viable STM test, named the Audible Contrast Threshold (ACT) test. First, an experimenter-controlled STM measurement paradigm was developed, in which the patient is presented binaurally with a continuous audibility-corrected noise via headphones and asked to press a pushbutton whenever they hear an STM target sound in the noise. The patient’s threshold is established using a Hughson-Westlake tracking procedure with a three-out-of-five criterion and then refined by post-processing the collected data using a logistic function. Different stimulation paradigms were tested in 28 hearing-impaired participants and compared to data previously measured in the same participants with an established STM test paradigm. The best stimulation paradigm showed excellent test-retest reliability and good agreement with the established laboratory version. Second, the best stimulation paradigm with 1-second noise “waves” (windowed noise) was chosen, further optimized with respect to step size and logistic-function fitting, and tested in a population of 25 young normal-hearing participants using various types of transducers to obtain normative data. Based on these normative data, the “normalized Contrast Level” (in dB nCL) scale was defined, where 0±4 dB nCL corresponds to normal performance and the greater the positive value of dB nCL, the greater the audible contrast loss. Overall, the results of the present study indicate that the ACT test may be considered a reliable, quick-and-simple (and thus clinically viable) test of STM sensitivity. The ACT can be measured directly after the audiogram using the same set up, adding only a few minutes to the process. CITE AS ### Competing Interest Statement All authors are employed by Demant A/S. ### Funding Statement This study was partially funded by the Innovation Fund Denmark (9090-00089B and 1044-00071B) and the William Demant Foundation (case number 20-2448). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Study A was approved by the Science-Ethics Committee for the Capital Region of Denmark (reference H-16036391). Study B was approved by the Science-Ethics Committee for the Capital Region of Denmark (reference H-1-2013-138). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors * ANOVA : Analysis of Variance ACT : Audible Contrast Threshold c/o : Cycles/Octave dB nCL : Decibel normalized Contrast Level DF : Diffuse Field ETML : Equivalent Threshold Modulation Level GUI : Graphical User Interface HI : Hearing-Impaired HL : Hearing Loss ICC : Intraclass Correlation Coefficient LME : Linear Mixed Effect MAF NH : Minimum Audible Field for Normal-Hearing listeners MAF TP : Minimum Audible Field for Test Participant FS : Full Scale NH : Normal-Hearing RETSPL : Reference Equivalent Threshold Sound Pressure Level SL : Sensation Level SPL : Sound Pressure Level STM : Spectro Temporal Modulation SRTs : Speech Reception Thresholds SD : Standard Deviation TCW : Threshold Candidate Window 2-AFC : Two-Alternative Forced-Choice 3-AFC : Three-Alternative Forced-Choice