PP311 - Effect of Assistive Listening Systems on Intelligibility Metrics in Various Real-World Environments

It is widely accepted that directional microphones and wireless assistive listening systems effectively improve the signal-to-noise ratio and perceptual speech intelligibility performance in background noise for hearing aid and cochlear implant users. Laboratory evaluations have been able to document the relative efficacy of these technologies in various configurations. However, many uncontrolled factors impact the potential benefit of assistive listening systems in ecological listening environments. We collected synchronous recordings obtained from hearing aid microphone and telecoil inputs and conducted non-invasive speech intelligibility analysis to help quantify the potential benefit of using wireless assistive listening systems in various real-world listening contexts.

Summary:

It is widely accepted that directional microphones and wireless assistive listening systems effectively improve the signal-to-noise ratio and perceptual speech intelligibility performance in background noise for hearing aid and cochlear implant users. In laboratory environments, the efficacy of directional microphones has been measured to range between 1 to 6dB, depending on the amount of venting in the user’s ear coupling and the degree of hearing loss [1], [2]. Remote microphones and FM systems have been demonstrated to provide even greater degrees of improvement (6 to 16.8 dB) depending on listener distance, the contribution from an environmental microphone, and the underlying wireless audio transmission technology [3].

However, many uncontrolled factors may impact the potential benefit of assistive listening systems in ecological listening environments. To access the real-world benefit of public hearing assistive technology, we first collected synchronous recordings obtained from hearing aid microphone and telecoil inputs. The binaural hearing instruments used during the real-world audio sample collection each had modified firmware that allowed them to wirelessly stream continuous audio input data, from either the microphone or telecoil, to a mobile smartphone for storage. The use of a binaural set of hearing devices allowed for the synchronous recording of both a hearing aid microphone and telecoil input.

Subsequently, we conducted an offline analysis of the real-world audio samples to estimate differences in background noise levels and the speech intelligibility advantage provided through the use of wireless assistive listening systems in various real-world listening contexts. Due to the ecological nature by which field audio samples were collected, a clean speech-reference signal was not available to support the analysis.  This restricted us to using a non-invasive measure of speech intelligibility. Thus, we chose to use Google Speech-to-Text recognizer performance as a metric as it has previously been demonstrated to be an accurate non-invasive instrumental intelligibility metric [4].

Results of the analysis will be shared for a variety of environments where public hearing assistive technology was available. 

References:

[1] F. Kuk, D. Keenan, and C. Ludvigsen, “Efficacy of an open-fitting hearing aid,” Hearing Review, vol. 12, no. 2, pp. 26–32, 2005.

[2] T. A. Ricketts and B. W. Y. Hornsby, “Directional hearing aid benefit in listeners with severe hearing loss,” International Journal of Audiology, vol. 45, no. 3, pp. 190–197, Jan. 2006, doi: 10.1080/14992020500258602.

[3] K. S. Rodemerk and J. A. Galster, “The Benefit of Remote Microphones Using Four Wireless Protocols,” Journal of the American Academy of Audiology, vol. 26, no. 8, pp. 724–731, Sep. 2015, doi: 10.3766/jaaa.15008.

[4] T. Betlehem, D. Marquardt, and M. McKinney, “Estimating Speech Intelligibility Using Google Speech-To-Text,” presented at the International Hearing Aid Research Conference, Tahoe City, CA, Aug. 13, 2022.