The effect of wearing face mask on speech intelligibility in listeners with sensorineural hearing loss and normal hearing sensitivity.

OBJECTIVE: This study aimed to investigate the effect of wearing a face mask on word recognition in hearing-impaired listeners. DESIGN: Word recognition scores were obtained in quiet and in different signal-to-noise ratios (SNRs 0, +5, and +10 dB) using two listening conditions (with N95 mask and with no-mask). STUDY SAMPLE: Participants were forty-six listeners with normal hearing sensitivity and thirty-nine listeners with mild to moderately severe sensorineural hearing loss. RESULTS: Results showed that wearing a face mask affected word recognition and that this effect was greater for listeners with hearing impairment than that observed for listeners with normal hearing sensitivity. The extent of this effect was also dependent on the SNR conditions such that the effect of wearing a face mask was worse in adverse listening conditions. CONCLUSIONS: Overall, this study demonstrated that face mask can disrupt speech intelligibility possibly by degrading some acoustical features which may pose substantial difficulties for those with hearing impairment.

Pediatric Arabic Closed-Set Word-Recognition Test: Development and Evaluation of Psychometric Characteristics.

BACKGROUND: Speech audiometry materials are widely available in many different languages. However, there are no known standardized materials for the assessment of speech recognition in Arabic-speaking children. PURPOSE: The aim of the study was to develop and validate phonetically balanced and psychometrically equivalent monosyllabic word recognition lists for children through a picture identification task. RESEARCH DESIGN: A prospective repeated-measure design was used. Monosyllabic words were chosen from children's storybooks and were evaluated for familiarity. The selected words were then divided into four phonetically balanced word lists. The final lists were evaluated for homogeneity and equivalency. STUDY SAMPLE: Ten adults and 32 children with normal hearing sensitivity were recruited. DATA COLLECTION AND ANALYSES: Lists were presented to adult subjects in 5 dB increment from 0 to 60 dB hearing level. Individual data were then fitted using a sigmoid function from which the 50% threshold, slopes at the 50% points, and slopes at the 20 to 80% points were derived to determine list psychometric properties. Lists were next presented to children in two separate sessions to assess their equivalency, validity, and reliability. Data were subjected to a mixed design analysis of variance. RESULTS: No statistically significant difference was found among the word lists. CONCLUSION: This study provided an evidence that the monosyllabic word lists had comparable psychometric characteristics and reliability. This supports that the constructed speech corpus is a valid tool that can be used in assessing speech recognition in Arabic-speaking children.

Hyperexcitability of the Nucleus Accumbens Is Involved in Noise-Induced Hyperacusis.

Reduced tolerance to sound stimuli (hyperacusis) is commonly seen in tinnitus patients. Dysfunction of limbic systems, such as the nucleus accumbens (NAc), may be involved in emotional reactions to the sound stimuli in tinnitus patients. To study the functional changes in the NAc in hyperacusis, we have examined the neural activity changes of the NAc using c-Fos staining in an animal model of hyperacusis. The c-Fos staining was also examined in the medial geniculate nucleus (MGN), a central auditory pathway which has neural projections to the NAc. Postnatal rats (14 days) were exposed to loud noise (115 dB SPL, 4 hours for two consecutive days) to induce hyperacusis (n = 4). Rats without noise exposure were used as the controls (n = 4). After P35, rats in both groups were put in a behavioral training for sound detection. After they were trained to detect sound stimuli, their reaction time to noise bursts centered at 2 kHz (40-110 dB SPL) was measured. Rats in the noise group showed a significantly shorter reaction time than those in the control group to the noise bursts at high intensities, suggesting the noise exposure induced hyperacusis behavior. The c-Fos expressions in the NAc and the MGNs of the noise group were significantly higher than those of the control group. Our results suggested that early-age noise exposure caused hyperactivity in the NAc and the MGNs which may induce the loudness increase in these rats.

Functional Change in the Caudal Pontine Reticular Nucleus Induced by Age-Related Hearing Loss.

Increased acoustic startle responses (ASR), which represent reduced uncomfortable loudness level in humans, have been reported in middle-aged C57BL/6J mice with sensorineural hearing loss. Although neural plasticity changes in the central auditory system after the peripheral lesions were suggested to underlie this phenomenon, the neurological cause of exaggerated ASR is still not clear. In this study, the local field potentials and firing rates of the caudal pontine reticular nucleus (PnC), which plays a major role in the ASR pathway, were recorded in 2-month- and 6-month-old C57BL/6 J mice. Consistent with our previous studies, the amplitude of ASR increased, and the threshold of ASR decreased in the 6-month-old mice after developing 20-40 dB hearing loss. The PnC response induced by high-frequency stimuli (>20 kHz) decreased in the 6-month group, whereas the PnC response induced by low-frequency stimuli (<12 kHz) showed a significant increase in the 6-month group compared to the 2-month group. The enhancement of PnC response is similar to the ASR increase found in the 6-month-old C57 mice. Our results suggest that the high-frequency hearing loss caused an increase in PnC sensitivity in the C57 mice which may enhance ASRs.

Hyperexcitability of inferior colliculus and acoustic startle reflex with age-related hearing loss.

Chronic tinnitus and hyperacusis often develop with age-related hearing loss presumably due to aberrant neural activity in the central auditory system (CAS) induced by cochlear pathologies. However, the full spectrum of physiological changes that occur in the CAS as a result age-related hearing loss are still poorly understood. To address this issue, neurophysiological measures were obtained from the cochlea and the inferior colliculus (IC) of 2, 6 and 12 month old C57BL/6J mice, a mouse model for early age-related hearing loss. Thresholds of the compound action potentials (CAP) in 6 and 12 month old mice were significantly higher than in 2 month old mice. The sound driven and spontaneous firing rates of IC neurons, recorded with 16 channel electrodes, revealed mean IC thresholds of 22.8 ± 6.5 dB (n = 167) at 2 months, 37.9 ± 6.2 dB (n = 132) at 6 months and 47.1 ± 15.3 dB (n = 151) at 12 months of age consistent with the rise in CAP thresholds. The characteristic frequencies (CF) of IC neurons ranged from 3 to 32 kHz in 2 month old mice; the upper CF ranged decreased to 26 kHz and 16 kHz in 6 and 12 month old mice respectively. The percentage of IC neurons with CFs between 8 and 12 kHz increased from 36.5% in 2 month old mice, to 48.8% and 76.2% in 6 and 12 month old mice, respectively, suggesting a downshift of IC CFs due to the high-frequency hearing loss. The average spontaneous firing rate (SFRs) of all recorded neurons in 2 month old mice was 3.2 ± 2.5 Hz (n = 167). For 6 and 12 month old mice, the SFRs of low CF neurons (<8 kHz) was maintained at 3-6 spikes/s; whereas SFRs of IC neurons with CFs > 8 kHz increased to 13.0 ± 15.4 (n = 68) Hz at 6 months of age and then declined to 4.8 ± 7.4 (n = 110) spikes/s at 12 months of age. In addition, sound-evoked activity at suprathreshold levels at 6 months of age was much higher than at 2 and 12 months of age. To evaluate the behavioral consequences of sound evoked hyperactivity in the IC, the amplitude of the acoustic startle reflex was measured at 4, 8 and 16 kHz using narrow band noise bursts. Acoustic startle reflex amplitudes in 6 and 12 month old mice (n = 4) were significantly larger than 2 month old mice (n = 4) at 4 and 8 kHz, but not 16 kHz. The enhanced reflex amplitudes suggest that high-intensity, low-frequency sounds are perceived as louder than normal in 6 and 12 month old mice compared to 2 month olds. The increased spontaneous activity, particularly at 6 months, may be related to tinnitus whereas the increase in sound-evoked activity and startle reflex amplitudes may be related to hyperacusis.

Early age noise exposure increases loudness perception - A novel animal model of hyperacusis.

The neural mechanisms that give rise to hyperacusis, a reduction in loudness tolerance, are largely unknown. Some reports suggest that hyperacusis is linked to childhood hearing loss. However, the evidence for this is largely circumstantial. In order to rigorously test this hypothesis, we studied loudness changes in rats caused by intense noise exposure (12 kHz narrow band noise, 115 dB SPL, 4 h) at postnatal 16 days. Rats without noise exposure were used as controls. The exposed noise group (n = 7) showed a mean 40-50 dB hearing loss compared to the control group (n = 8) at high frequencies (>= 8 kHz) and less hearing loss at lower frequencies. Loudness was evaluated using sound reaction time and loudness response functions in an operant conditioning-based behavioral task using narrow-band noise (40-110 dB SPL, centered at 2, 4 and 12 kHz). Interestingly, the sound reaction time of the noise group was significantly shorter than the control group at supra-threshold levels. The average reaction time was less than 100 ms in the noise group at 100 dB SPL, which was three times shorter than the control group. Our results indicate that early noise-induced hearing loss leads to a significant increase of loudness, a behavior indicative of hyperacusis. Our results are consistent with clinical reports suggesting that hearing loss at an early age is a significant risk factor for hyperacusis.