Lower Hearing Thresholds Research Articles

Clinical Features of Sudden Sensorineural Hearing Loss in Diabetic Patients

Clinical studies of sudden sensorineural hearing loss (SSNHL) rarely focus on diabetic patients. We attempted to elucidate the clinical features of SSNHL in diabetic patients and to evaluate the factors influencing hearing deficits. Retrospective. A retrospective review of diabetic patients with SSNHL was conducted at National Taiwan University Hospital from 1984 to 2003. The demographic and clinical characteristics, audiometries, and course of hearing recovery were reviewed. Sixty-seven patients (38 men and 29 women) with a mean age of 60.1 +/-11.9 years were recruited. The mean duration of diabetes was 7. 5 +/- 7.7 years. The mean fasting plasma glucose (FPG), postprandial plasma glucose (PPG), and glycosylated hemoglobin (HbA1C) at admission were 12.4 +/- 5.3 mmol/L, 14.5 +/- 5.4 mmol/L, and 9.9 +/- 2.9 mmol/L, respectively. Profound hearing loss was very common in this series (44.8%). Hearing impairment was also noted in the opposite ear, especially in the high frequencies. Presenting symptoms, the duration of diabetes, the FPG, and the HbA1C had no significant correlations with the severity of hearing loss. After adjusting for sex and age, a high PPG level was significantly associated with opposite-ear hearing deficits in the middle frequencies. In follow-up, the low and middle tone hearing thresholds in the lesion ears improved more than that at high frequencies, but they still did not return to baseline. Hearing consistently improved within 2 months after disease onset, but improvements were rare thereafter. With suitable treatment, optimal glycemic control could be achieved even under high-dose steroid regimens. In diabetic patients with SSNHL, hearing loss in the contralateral ear and the profound type hearing loss in the lesion ear were commonly noted. The age and PPG level had significant correlations to contra-ear hearing loss. The poor prognosis of sudden deafness in diabetes patients may be caused by preexisting microvascular lesions in the inner ear, and the PPG level could be a risk factor indicator for cochlear dysfunction in diabetic patients. High-dose glucocorticoid should not be contraindicant in diabetic patients with SSNHL. Whether a longer duration of treatment will result in more hearing improvement is worthy of further study.

Audiological Profile in Older Children and Adolescents with Unrepaired Cleft Palate

To study the audiological profile in the cleft population comprising older children and adolescents with unrepaired cleft palate and to arrive at a consensus regarding management of otitis media with effusion in this unique group. Tertiary care institute in Chandigarh, Punjab, India. Prospective study based on all patients older than 7 years with unrepaired cleft palate, attending the plastic surgery outpatient department, Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, Punjab, India, from January 2001 to December 2002. Patients with submucous cleft were excluded from the study. General characteristics, otoscopic findings, pure tone audiometry, and impedence audiometry of all patients were recorded. Patients' ages ranged from 8 to 18 years, with a mean of 10.5 years. Regarding otological complaints, 86.7% were asymptomatic. Otoscopic findings revealed mild retraction as the most common finding in 50% of the ears. Type B curve was the most common tympanometric finding. The highest and lowest hearing thresholds recorded were 45 db and 15 db, respectively, with a mean of 27.11 db. The audiological profile of this unique group, which neither had undergone palatoplasty nor had received treatment for the ear condition, demonstrates a mild to moderate hearing impairment. This definitely requires treatment, but owing to the lack of a prospective control group, it is difficult to conclude whether these patients are benefited by conservative treatment alone or by an early aggressive surgical treatment for otitis media with effusion (OME).

Processamento auditivo e audiometria de altas freqüências em escolares de São Paulo

Auditory processing and auditory sensibility to high Frequency sounds. To characterize the localization processes, temporal ordering, hearing patterns and detection of high frequency sounds, looking for possible relations between these factors. 32 hearing fourth grade students, born in city of São Paulo, were submitted to: a simplified evaluation of the auditory processing; duration pattern test; high frequency audiometry. Three (9,4%) individuals presented auditory processing disorder (APD) and in one of them there was the coexistence of lower hearing thresholds in high frequency audiometry. APD associated to an auditory sensibility loss in high frequencies should be further investigated.

Higher serum aldosterone correlates with lower hearing thresholds: A possible protective hormone against presbycusis

Aldosterone hormone is a mineralocorticoid secreted by adrenal gland cortex and controls serum sodium (Na +) and potassium (K +) levels. Aldosterone has a stimulatory effect on expression of sodium–potassium ATPase (Na, K-ATPase) and sodium–potassium–chloride cotransporter (NKCC) in cell membranes. In the present investigation, the relation between serum aldosterone levels and age-related hearing loss (presbycusis) and the correlation between these levels versus the degree of presbycusis in humans were examined. Serum aldosterone concentrations were compared between normal hearing and presbycusic groups. Pure-tone audiometry, transient evoked otoacoustic emissions (TEOAE), hearing in noise test (HINT) and gap detection were tested for each subject and compared to the serum aldosterone levels. A highly significant difference between groups in serum aldosterone concentrations was found ( p = 0.0003, t = 3.95, df = 45). Highly significant correlations between pure-tone thresholds in both right and left ears, and HINT scores versus serum aldosterone levels were also discovered. On the contrary, no significant correlations were seen in the case of TEOAEs and gap detection. We conclude that aldosterone hormone may have a protective effect on hearing in old age. This effect is more peripheral than central, appearing to affect inner hair cells more than outer hair cells.

Lower Hearing Threshold by Noise

We demonstrate that noise can be a benefit factor that enables us tohear weaker signals. We measured the hearing thresholds of subjects forpure tone in different noise levels. The results show that pure tonethresholds with noise of some levels are lower than that without noise.The largest down-shift of the threshold by noise among the examinedsubjects is 5.7 dB, and the smallest is 1.7 dB.

Electrode impedance in adults and children using the Nucleus 24 cochlear implant system

This study measured changes in electrode impedance over time in 19 adults and 29 children implanted with the Nucleus 24 cochlear implant system, using common ground and three monopolar modes of stimulation, over a series of time intervals. Impedances increased from the intraoperative to the initial fitting session, decreased during the initial fitting session and for the following week, and were then stable. Impedances were lowest for the common ground mode, while for the monopolar modes, impedances were related to the surface area of the return electrode. Impedances for children were higher than those for adults at the initial fitting session and for the following three weeks. The clinically measured impedance values increased in a basal-to-apical direction. When these data were corrected for differences in electrode surface area, impedances decreased in a basal-to-apical direction. Impedances were influenced by whether the electrodes were stimulated or unstimulated. Adults with higher electrode impedances tended to have lower hearing thresholds and comfortable listening levels, but this did not appear to clearly be the case for children.

Relationships between reading, phonological skills and language development in individuals with Down syndrome: a five year follow up study

This article is based on language, memory andreading information gathered for a five yearfollow-up study of 30 children and adolescentswith Down syndrome, aged from 10 to 24 years atthe end of the study. At Time 1, 10individuals were classified as readers but byTime 2 this number had risen to 16. Readers significantly outperformed non-readerson tests of nonverbal ability, languagecomprehension and production, phonologicalmemory and phonological awarenesss. However,some of these differences could be accountedfor by readers' significantly lower hearingthresholds. Phonological memory and earlyletter knowledge at Time 1 were significantpredictors of reading scores for Time 2readers, after controlling for age, nonverbalability and corresponding Time 1 readingscores. There was no evidence that learning toread had a significant impact on later languagecomprehension, but early reading skills may besignificant predictors of MLU five years later,after controlling for age, nonverbal abilityand hearing.

On Inner Ear Function and the Origin of Oto-acoustic Emissions

The extremely low hearing threshold of the mammalian ear suggests the presence of a special amplifying mechanism, because the stereocilia of the outer hair cells (OHCs) are not likely to be sensitive enough themselves, although their mechanical embedding may provide some amplification. In the past decades, biophysicists have increasingly turned to the chaos theory for explanation, a theory the implications of which are considerable. One of its major tenets, self-organization, is not easily understood at first glance, but is easily reproducible mathematically. With self-organization, the processes involving the OHCs can readily be simulated: Self-organization can help to explain why OHCs vibrate at amplitudes much higher than those of the exciting stimulus. To further our understanding of the process of hearing, vibratory processes, which presumably occur in normal and damaged OHC clusters, are described and compared with a mathematical analysis of data sets obtained from normal subjects using an extremely sensitive microphone.

Do large bushcrickets have more sensitive ears? Natural variation in hearing thresholds within populations of the bushcricket Requena verticalis (Listroscelidinae: Tettigoniidae)

The auditory spiracle of tettigoniid Orthoptera influences hearing threshold and, for the most part, individuals with larger auditory spiracles have lower hearing thresholds; they are more sensitive. Hearing thresholds of both sexes of the bushcricket, Requena verticalis Walker (Orthoptera; Tettigoniidae; Listroscelidinae), were measured at the male call’s carrier frequency and were found to correlate with spiracle dimension. In turn, spiracle dimension correlates with the size of the insect as measured by pronotum length. The best frequency of hearing is close to 16 kHz and this appears to be independent of size. Males show a higher variation in threshold than females and this was reflected in a trend toward lower variance in spiracle size in females.To test the effects of size on sensitivity, spiracle size was manipulated by partially blocking it. Blocking the spiracle decreases sensitivity to high rather than low frequencies. As in other tettigoniids, the spiracle and associated auditory system act as a high‐pass filter. Within and between sex differences in hearing sensitivity were compared with differences in male call intensity. It is argued that sensitivity to sounds associated with mating should be as much under sexual selection as the sexual calls of males.

Correlation between auditory sensitivity and vocalization in anabantoid fishes.

Several anabantoid species produce broadband sounds with high-pitched dominant frequencies (0.8-2.5 kHz), which contrast with generally low-frequency hearing abilities in (perciform) fishes. Utilizing a recently developed auditory brainstem response recording-technique, auditory sensitivities of the gouramis Trichopsis vittata, T. pumila, Colisa lalia, Macropodus opercularis and Trichogaster trichopterus were investigated and compared with the sound characteristics of the respective species. All five species exhibited enhanced sound-detecting abilities and perceived tone bursts up to 5 kHz, which qualifies this group as hearing specialists. All fishes possessed a high-frequency sensitivity maximum between 800 Hz and 1500 Hz. Lowest hearing thresholds were found in T. trichopterus (76 dB re I microPa at 800 Hz). Dominant frequencies of sounds correspond with the best hearing bandwidth in T. vittata (1-2 kHz) and C. lalia (0.8-1 kHz). In the smallest species, T. pumila, dominant frequencies of acoustic signals (1.5-2.5 kHz) do not match lowest thresholds, which were below 1.5 kHz. However, of all species studied, T. pumila had best hearing sensitivity at frequencies above 2 kHz. The association between high-pitched sounds and hearing may be caused by the suprabranchial airbreathing chamber, which, lying close to the hearing and sonic organs, enhances both sound perception and emission at its resonant frequency.

Radiation hazard assessment of pulsed microwave radars.

Observed biological effects of pulsed microwave radiation are reviewed and the exposure standards for microwave radiation are summarized. The review indicates that the microwave auditory effect is the only well-established specific effect in realistic exposure situations. The threshold for the effect depends on the energy density per pulse and may be as low as 20 mJ/m2 for people with low hearing threshold. Energy density limits have been included in the most recent exposure standards. A new battery-operated, hand-held meter developed for measurements of pulse power densities around scanning radar antennas is described, and a simple new model for the calculation of power density in the main beam of radar antennas is presented. In the near field measured values differed from the calculated values by 2-3 dB.

Low Frequency Hearing Threshold Determination in Newborns, Infants and Mentally Retarded Children by Middle Latency Responses

Middle latency (10-50 ms) responses (MLR) evoked by tone-pips (1,000 Hz 500 Hz) and early (0-10 ms) auditory evoked potentials (EAEP) evoked by chicks were recorded on 68 newborn babies (premature or at term), infants and children, some with central nervous system or psychiatric disorders, who had normal or impaired hearing. MLR were obtained either during sleep, chloral-hydrate sedation or ketamine anesthesia. Thresholds estimated from MLR and EAEP were compared to those from subsequent psychoacoustic pure tone testing. We confirm that MLR provide good threshold estimates for hearing in the low frequency range, whereas click evoked EAEP are good threshold indicators only for high frequencies.

Low Frequency Hearing Thresholds in Pressure Field and in Free Field

Thresholds of hearing Were determined in pressure field at frequencies from 4 Hz to 125 Hz. At the frequencies 4–25 Hz hearing thresholds were found that are in the lower middle of the range already reported by other investigators. At frequencies from 25 Hz to 1 kHz thresholds have already been determined in free field by the same method and using the same subjects. The two investigations overlap at frequencies from 25 Hz to 125 Hz, and in this range the results were almost identical. The differences were below 1 dB, except at 63 Hz where the difference was 2.5 dB. None of the differences was significant in a t-test.

Repeatability of high-frequency bone conduction thresholds.

The purpose of this study was to determine the repeatability of high-frequency, bone conduction thresholds and to increase the data base concerning high-frequency, bone conduction threshold levels. Bone conduction thresholds were obtained on 30 subjects having normal, low, and mid frequency (0.25 to 8 kHz) hearing thresholds within and across five test sessions using a Pracitronic KH 70 bone vibrator referenced to a Brüel and Kjaer 4930 mechanical coupler at 1, 4, 8, 10, 12, 14, and 16 kHz. Within and across sessions, the bone conduction thresholds were not significantly (p greater than 0.05) different at each frequency indicating that repeated testing without replacing the bone vibrator (within session) and with replacing the bone vibrator (across session) did not influence the threshold measurements. Clinical implications concerning high-frequency, bone conduction audiometry are discussed.

難聴幼小児における耳掛型補聴器装用 箱型補聴器との比較

This study was designed to compare the usefulness of hearing aids between behind-the-ear type and box type in hearing impaired children, as regards to the hearing threshold with hearing aid and it using situation in every day life. Thirty-seven hearing impaired children were investigated in this study.It was clarified that many children showed lower hearing threshold with behind-the-ear type hearing aid than those with box type hearing aid, and also that reducing behavioral difficulties, minimizing psychological annoyance and increasing motivation to use hearing were noticed in the cases of behind-the-ear type hearing aid.