Mass and stiffness affect on the peculiar characteristics of transmission of the middle ear and the distinctive behavior of the cochlear mechanics. Applying the principle of the mass and stiffness, the band-pass characteristic transfer function of the middle ear has been explained. The greatest transfer function of the middle ear, approximately 24-29 dB, is observed at 1-2 kHz in both cat and human species. However, at lower frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear cavity. At higher frequencies, the transfer function was disturbed by the stiffness of the middle ear primarily due to middle ear bones. Several examples, such as an acoustic reflex, otitis media, and otosclerosis are discussed. For understanding the traveling wave of the basilar membrane, different place tuning at certain stimulus frequencies, contrastingly shaped basilar membrane to the cochlear duct, and the structural and physical characteristics of the whole cochlear partition were reviewed in terms of changing width, mass, and stiffness from the base to apex. Being about ten times wider, more massive, and one hundredfold stiffer at the base than the apex, the nature of the cochlear partition to absorb high-frequency energy changes in fluid pressure declines toward the apex. Consequently, at the base of the cochlea, high frequencies stimuli are decoded while low frequencies stimuli are decoded at the apex of the cochlea. Due to these characteristics of the cochlear partition, the direction of the traveling wave was also proved to be in the fashion of base-to-apex always.

This preliminary study assessed the effects of noise and stimulus presentation order on recall of spoken words and recorded pupil sizes while normal-hearing listeners were trying to encode a series of words for a subsequent recall task. In three listening conditions (stationary noise in Experiment 1; quiet versus four-talker babble in Experiment 2), participants were assigned to remember as many words as possible to recall them in any order after each list of seven sentences. In the two noise conditions, lists of sentences fixed at 65 dB SPL were presented at an easily audible level via a loudspeaker. Reading span (RS) scores were used as a grouping variable, based on a median split. The primacy effect was present apart from the noise interference, and the high-RS group significantly outperformed the low-RS group at free recall measured in the quiet and four-talker babble noise conditions. RS scores were positively correlated with free-recall scores. In both quiet and four-talker babble noise conditions, sentence baselines after correction to the initial stimulus baseline increased significantly with increasing memory load. Larger sentence baselines but smaller peak pupil dilations seemed to be associated with noise interruption. The analysis method of pupil dilation used in this study is likely to provide a more thorough understanding of how listeners respond to a later recall task in comparison with previously used methods. Further studies are needed to confirm the applicability of our method in people with impaired hearing using multiple repetitions to estimate the allocation of relevant cognitive resources.

Objectives. This study evaluated the electroacoustic characteristics of smartphone-based hearing aid applications (apps).Methods. We investigated hearing aid apps based on processing delay measurements, hearing instrument testing, simulated real ear measurements, and a head-and-torso simulator.Results. Many apps exceeded the recommended level for processing delay. Hearing instrument testing showed the highest amplification characteristics and the best sound quality when a hearing aid was used, followed by the high-end apps and then the low-end apps. The simulated real ear measurements results showed that the high-end apps had a better ability to match the amplification targets than the low-end apps, but there was no consistent pattern among apps when controlling the output. Only a few apps could improve the signal-to-noise ratio in the head-and-torso simulator.Conclusion. Most of the apps showed relatively poor electroacoustic performance in comparison with hearing aids. Generalizing access to hearing care through hearing aid apps induces a wide diversity of hearing performance with no fixed standard for reliability. However, we expect their overall quality to improve over the next few years.

Using behavioral evaluation of free recall performance, we investigated whether reverberation and/or noise affected memory performance in normal-hearing adults. Thirty-four participants performed a free-recall task in which they were instructed to repeat the initial word after each sentence and to remember the target words after each list of seven sentences, in a 2 (reverberation) × 2 (noise) factorial design. Pupil dilation responses (baseline and peak pupil dilation) were also recorded sentence-by-sentence while the participants were trying to remember the target words. In noise, speech was presented at an easily audible level using an individualized signal-to-noise ratio (95% speech intelligibility). As expected, recall performance was significantly lower in the noisy environment than in the quiet condition. Regardless of noise interference or reverberation, sentence- baseline values gradually increased with an increase in the number of words to be remembered for a subsequent free-recall task. Long reverberation time had no significant effect on memory retrieval of verbal stimuli or pupillary responses during encoding.

BACKGROUND: The aim of this study was to evaluate the behavioral performance of a selection of currently available hearing aid apps in patients with mild hearing loss. METHODS: We investigated 3 user-friendly hearing aid apps (EarMachine, Sound Amplifier, and Petralex) with real-ear measurement, warbletone audiometry, word recognition testing in unaided and aided conditions, and hearing-in-noise tests in quiet and noise-front conditions in a group of users with mild hearing impairment (n=7) as a pilot for a future long-term investigation. Results from the apps were compared with those of a conventional hearing aid. RESULTS: Hearing aids showed greater gain at 1 and 3 kHz than hearing aid apps in real-ear insertion gain of real-ear measurements. Hearing aids tended to have greater gain than hearing aid apps at 2 and 3 kHz in the sound field audiometry test. The clinical performance of the listeners tended to be better when using a hearing aid and Petralex (13% and 6% improvement in word recognition score, respectively), while EarMachine and Sound Amplifier conferred limited user benefit. The hearing aid apps did not improve signal-to-noise ratio in comparison with the unaided condition in the hearing-in-noise test. CONCLUSIONS: Some hearing aid apps were beneficial for patients with mild hearing loss in terms of amplification, but participants using the apps showed no improvements in hearing-in-noise tests. Cite this article as: Koo M, Nguyen W, Lee JH, Oh S-H, Park MK. Behavioral evaluation of 3 smartphone-based hearing aid apps for patients with mild hearing loss: an exploratory pilot study. J Int Adv Otol. 2022;18(5):399-404.

BACKGROUND Underuse of hearing aids is caused by several factors, including the stigma associated with hearing disability, affordability, and lack of awareness of rising hearing impairment associated with the growing population. Thus, there is a significant opportunity for the development of direct-to-consumer devices. For the past few years, smartphone-based hearing-aid apps have become more numerous and diverse, but few studies have investigated them. OBJECTIVE This study aimed to elucidate the electroacoustic characteristics and potential user benefits of a selection of currently available hearing-aid apps. METHODS We investigated the apps based on hearing-aid control standards (American National Standards Institute) using measurement procedures from previous studies. We categorized the apps and excluded those we considered inefficient. We investigated a selection of user-friendly, low-end apps, EarMachine and Sound Amplifier, with warble-tone audiometry, word recognition testing in unaided and aided conditions, and hearing-in-noise test in quiet and noise-front conditions in a group of users with mild hearing impairment (n = 7) as a pilot for a future long-term investigation. Results from the apps were compared with those of a conventional hearing aid. RESULTS Five of 14 apps were considered unusable based on low scores in several metrics, while the others varied across the range of electroacoustic measurements. The apps that we considered “high end” that provided lower processing latencies and audiogram-based fitting algorithms were superior overall. The clinical performance of the listeners tended to be better when using hearing aid, while the low end hearing-aid apps had limited benefits on the users. CONCLUSIONS Some apps showed the potential to benefit users with limited cases of minimal or mild hearing loss if the inconvenience of relatively poor electroacoustic performance did not outweigh the benefits of amplification.