LM105 - A Reliable Two-Minute Noise Acceptance Test that Predicts More than Hearing Aid Acceptance

Abstract:
Knowing if a patient would potentially accept hearing aids (HA) could provide insights in the HA selection and counseling process. The Tracking of Noise Tolerance (TNT) test allows us to track the level of noise that listeners are willing to accept while understanding >90% of the words. The results predict HA satisfaction and allow HA fine-tuning and validation. Additionally, it reflects sensory gating and estimates subjective speech intelligibility.

Summary:
A common complaint from hearing aid wearers is using their hearing aids (HA) in noise. Because individual wearers have different degrees of acceptance of noise (among other differences), the same hearing aids, or hearing aids with different features may yield different levels of satisfaction in real life. Thus a tool that can evaluate noise acceptance could help ensure the patient’s satisfaction with the hearing aids in noisy environments. And if the tool can predict potential HA satisfaction, it would also make the HA selection (and counseling) process less challenging for the clinician.

Noise acceptance is traditionally measured using the Acceptable Noise Level (ANL) test. We were inspired by the ANL but felt that the test can be improved in its test-retest reliability and the information it provides. Thus, four years ago we started evaluating the Tracking of Noise Tolerance (TNT) test. This test fixes the speech level (at 75 and/or 82 dB SPL), and have listeners adjust the level of a competing background noise (via Bekesy tracking using the spacebar on the computer keyboard) so that the noise is at the maximum level that they can put up with while still understanding over 90% of the speech passage. We have used the test on hearing impaired and normal hearing subjects in a series of experiments in the last 4 years. In the first experiment, we have demonstrated a test-retest reliability of 2 dB, small enough to demonstrate quantitative differences in processing between hearing aids. In the second study, we were able to show that people who have a higher tolerance for noise are also more satisfied with their hearing aids in loud, noisy situations. In the third study, we were able to demonstrate that the test can be used for fine-tuning and measuring HA feature efficacy.

In the last two years, we were interested to understand WHY listeners performed in the manner they did on the TNT. To do that, we formalized the TNT test development and determined the list equivalence of the eight passages one can use during the test. We also took the TNT passages and measured the subjective and objective performance-intensity functions over a range of signal-to-noise ratios (SNRs, from -9 to +3) in normal-hearing listeners. We then relate the performance on the subjective and objective intelligibility tests to the TNT values (which is a noise-to-signal ratio, NSR) in order to understand the intelligibility at the TNT threshold and any intelligibility change during tracking (between peaks and valleys). Indeed, we are able to demonstrate that intelligibility at the valleys of the TNT tracking is around the 90% criterion we instructed the listeners.

Furthermore, we are able to show that the magnitude of the tracking is highly correlated with the cortical response (P1N1P2) during sensory gating measurements.

In this presentation, we will review the studies we have completed on the TNT test and outline a protocol where clinicians can use it to better understand their patients and select/fine-tune hearing aids to maximize HA satisfaction.