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Results for “Auditory Threshold”

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At least 577 records · Page 32Linked to original sources

PubMed2003

Low-frequency hearing assessment by middle latency responses in children with pervasive developmental disorder.

OBJECTIVE: In this study, we assessed middle latency responses (MLR) in children diagnosed with pervasive developmental disorder (PDD) in order to detect low-frequency auditory thresholds. METHODS: 35 children, 25 males and 10 females, aged below 5, diagnosed with PDD were referred to rule out any possible hearing deficit. Audiologic evaluation included free-field testing, tympanometry, and both MLR and auditory brainstem responses. A control group of 15 normal children matched for sex and age were used. RESULTS: In 9 out of 35 children (25%), low-frequency sensory hearing loss was revealed. The hearing loss was unilateral in seven children and bilateral in two, and varied from slight to severe. In four out of the nine cases (44%), parents had not suspected hearing loss, since these children always responded to sound. CONCLUSIONS: Among children diagnosed with PDD a significant proportion (25%) was affected by low-frequency sensory hearing loss, detected by MLR. In these children, when low-frequency hearing loss was found bilateral or severe unilateral, aural rehabilitation was initiated in order to improve their responses to auditory stimuli and their impaired communication with the environment. PDD children, even if their reaction to sound is normal, must be referred to thorough audiometric evaluation while low-frequency hearing level should always be tested.

Acoustic Impedance Tests↗

PubMedDate not supplied

A slow brain stem response for low-frequency audiometry.

Proper choices of stimuli and of brain stem electric responses allow us to estimate peripheral auditory thresholds at 500, 1 000, 2 000 and 4 000 Hz with an accuracy of about +/- 10 dB. With the help of sedation (secobarbital), such audiograms may be obtained from each ear of a child of any age in a single session. Tone pips (filtered clicks) or very brief tone bursts give a frequency selectivity that is clinically adequate. The rise time must be adjusted to the center frequency. A rise time of two periods with a plateau from zero to one period gives a good compromise between frequency specificity and a synchronous neural discharge. The best threshold indicator for tone pips of 2 000 Hz or higher (or unfiltered clicks) is P6 (Jewett V). At 60 dB nHL its latency is 6.0-7.0 ms (for children of 1 year or older), but near threshold it is 8.0-9.5 ms. An input pass-band of 140-3 000 Hz is appropriate. The best threshold indicator at 500 or 1 000 Hz is a nearly neglected slower wave with a scalp-negative crest at about 10 ms following a 60-dB click. Latency is 15 ms following a 500-Hz tone pip at 15 dB SL. We call this wave "slow negative (ten)" or SN10. To see it well a wider input pass-band such as 40-3 000 Hz is needed. SN10 is usually obscured by P6 or by frequency-following response at stimulus levels above 35 dB SL. The details are given of a clinical routine that allows the determination (+/- 10 dB) of 8 threshold endpoints within about 80 min. Several precautions and limitations are discussed, and also the origin of the SN10 wave.

Audiometry↗

PubMed1981

Acoustic reflex thresholds in young and elderly subjects with normal hearing.

This study replicated Silman's [J. Acoust. Soc. Am. 66 (1979a)] experiment comparing acoustic reflex thresholds in normal hearing young and elderly subjects. The original study was modified so that the criterion for normal hearing was extended through 8000 Hz, and the range of auditory thresholds among the younger group was selected to approximate those of the elderly subjects as closely as possible. The data confirmed those reported by Silman, showing an elevation of the ART for broadband noise, but nor for tonal activators in the elderly group.

Adult↗

PubMed2006

Saccular potentials of the vocal plainfin midshipman fish, Porichthys notatus.

The plainfin midshipman fish, Porichthys notatus, is a vocal species of teleost fish that generates acoustic signals for intraspecific communication during social and reproductive behaviors. All adult morphs (females and males) produce single short duration grunts important for agonistic encounters, but only nesting males produce trains of grunts and growls in agonistic contexts and long duration multiharmonic advertisement calls to attract gravid females for spawning. The midshipman fish uses the saccule as the main acoustic endorgan for hearing to detect and locate vocalizing conspecifics. Here, I examined the response properties of evoked potentials from the midshipman saccule to determine the frequency response and auditory threshold sensitivity of saccular hair cells to behaviorally-relevant single tone stimuli. Saccular potentials were recorded from the rostral, medial and caudal regions of the saccule while sound was presented by an underwater speaker. Saccular potentials of the midshipman, like other teleosts, were evoked greatest at a frequency that was twice the stimulus frequency. Results indicate that midshipman saccular hair cells of non-reproductive adults had a peak frequency sensitivity that ranged from 75 (lowest frequency tested) to 145 Hz and were best suited to detect the low frequency components (<or=105 Hz) of midshipman vocalizations.

Acoustic Stimulation↗

PubMed1988

Reference threshold sound-pressure levels for the TDH-50 and ER-3A earphones.

Reference threshold sound-pressure levels were established for a new insert earphone, the ER-3A tubephone, and for the TDH-50 earphone. In test-retest comparisons, the tubephone produced estimates of auditory threshold as reliable as the thresholds produced by the supraaural earphone. Reference thresholds were developed for the two earphones from data contributed by three laboratories. While the TDH-50 data are in good agreement with the provisional ANSI 6-cc coupler reference levels (ASHA, 1982), the ER-3A data are at variance with the manufacturer's provisional recommendation for 2-cc coupler reference thresholds for frequencies below 1 kHz. The differences are attributed to physiologic noise that masked the lower frequency thresholds.

Acoustic Stimulation↗

PubMed1988

Infant thresholds with enhanced attention to the signal in visual reinforcement audiometry.

Experimental data show a discrepancy between adult auditory thresholds and best estimates of infant thresholds. The source of the discrepancy has not been determined. Attentional differences between infants and adults and procedural differences to accommodate infant attentional behavior may account at least in part for the discrepancy. A standard operant procedure, Visual Reinforcement Audiometry (VRA), was modified to enhance infant attention to impending auditory signals. Results on 16 infants evaluated with conventional VRA and modified VRA revealed an average 5.5 dB improvement in threshold with the modified technique. Correction for adult performance in similar tasks indicated a 3.3 dB attentional effect between infant and adult thresholds. The shift in threshold reflects on the adequacy of VRA as a threshold procedure.

Adult↗

PubMed2002

Amphibious auditory responses of the American alligator (Alligator mississipiensis).

Animals that thrive both on land and underwater are faced with the task of interpreting stimuli in different media. This becomes a challenge to the sensory receptors in that stimuli (e.g., sound, motion) may convey the same type of information but are transmitted with different physical characteristics. We used auditory brainstem responses to examine hearing abilities of a species that makes full use of these two environments, the American alligator (Alligator mississipiensis). In water, alligators responded to tones from 100 Hz to 2,000 Hz, with peak sensitivity at 800 Hz. In air, they responded to tones from 100 Hz to 8,000 Hz, with peak sensitivity around 1,000 Hz. We also examined the contribution to hearing of an air bubble that becomes trapped in the middle ear as the animal submerges. This bubble has been previously implicated in underwater hearing. Our studies show that the trapped air bubble has no affect on auditory thresholds, suggesting the bubble is not an important adaptation for underwater hearing in this species.

Air↗

PubMedDate not supplied

[Acoustically evoked brain stem potentials in infants with velum clefts].

Brainstem acoustic evoked responses were recorded from 37 infants with cleft palate. Only 35% presented normal auditory thresholds. 27% had a bilateral 22% a unilateral hearing deficit of more than 30 dB. Controls after operative closure of the cleft showed no improvement of the conductive hearing loss.

Auditory Threshold↗

PubMed1994

Audiologic manifestations in fetal alcohol syndrome assessed by brainstem auditory-evoked potentials.

In 29 of 36 children with fetal alcohol syndrome brainstem auditory-evoked potentials were performed and the auditory threshold was determined. The hearing of patients with a pathologic finding was then subject to a thorough ear-nose-throat examination. Additionally the IQ was determined and an audiolinguistic examination was carried out. Seventy-five % of the children showed a peripheral hearing disorder on the basis of conductive hearing loss. In two children (7%) sensorineural hearing loss was located to the inner ear. A dysfunction of the auditory pathway was found in 6 patients (21%). The results of an isolated ear-nose-throat examination in 7 further children supported these findings. The mean performances in the linguistic tests were far below average and displayed a strong relation to the IQ. This study shows that a peripheral hearing disorder, especially an obstruction of the auditory tube as well as dysfunctions of the inner ear and the central hearing pathway, are different manifestations of the fetal alcohol syndrome. An etiologic connection between craniofacial abnormalities in these children and an increased susceptibility to peripheral hearing disorders could not be demonstrated. To avoid a retardation of the linguistic development in addition to the intellectual deficits a strong emphasis must be put on an early and comprehensive auditory examination of children with FAS.

Adolescent↗

PubMed1985

Relation between frequency selectivity and speech perception following glycerol-induced cochlear changes.

Changes in auditory threshold, psychophysical tuning curves, and speech perception (in both quiet and noise) were monitored over a 3-hr period following the ingestion of glycerol. All listeners had sensorineural hearing loss secondary to Menière's disease. Findings were characterized by large intersubject variability and in general did not show a clear relation between changes in threshold, frequency resolution, and speech perception.

Adult↗

PubMed1993

Temporal patterns of transient-evoked otoacoustic emissions in normal and impaired cochleae.

The spatial distribution of outer hair cells that participate in generating transient-EOE frequency-components has been investigated in man. According to several models (e.g. Wilson (1990) Hear. Res. 2, 527-532; Zwicker (1986) J. Acoust. Soc. Am. 80, 154-162; Wilson and Kemp (Eds.), Cochlear Mechanisms, Structures, Functions and Models, Plenum Press, NY), EOEs result from interferences between broadly distributed contributions, responsible for their long frequency-dependent delay. This work presents an analysis of the temporal patterns of click- and tone-burst-EOEs in human ears when contributions to EOEs are reduced by noise-induced lesions with audiometric notches centred around 4 kHz (N = 46). Although the auditory thresholds at the frequencies of the studied EOE-components were always normal, these components exhibited drastic and predictable changes compared to normal control ears (N = 40). (1) Their temporal pattern at the highest EOE frequency fmax just below the audiometric notch appeared to be determined by the cochlear state at high frequencies (6 to 8 kHz). Either it was normal and the EOE exhibited a complicated beat-structure, or it was impaired and the time envelope of the EOE was simple. In contrast, any type of time pattern could be observed in normal ears. (2) The temporal patterns of EOEs one octave below fmax always presented many beats and short delays. The proposed interpretation is that contributions to a transient-EOE component at frequency f can come from distant basal cochlear areas, i.e. more than 1 and sometimes 1.5 octaves from the place tuned to f. Therefore, the possible relationships between transient-EOEs and tuning mechanisms which presumably involve only a small number of OHC need further investigations.

Acoustic Stimulation↗

PubMed1990

Cochlear damage and increased threshold in alpha-difluoromethylornithine (DFMO) treated guinea pigs.

Alpha-difluoromethylornithine (DFMO) inhibits polyamine synthesis and is used as an antineoplastic and antiparasitic drug. In early human trials DFMO unexpectedly caused a sensorineural hearing loss. In the current study DFMO was administered to guinea pigs to investigate its effects on organ of Corti histology and on auditory thresholds. Histologic examination revealed that DFMO caused greatest damage in the hook and first turn. Damage in the second and third turns was minimal. Animals treated for 12 weeks with DFMO differed significantly (P less than 0.05) from controls in the hook and first turn in that: 1) DFMO caused a loss of hair cells in all rows. Loss of inner hair cells was greater than that of outer hair cells. 2) The remaining outer hair cells were shorter and contained a greater number of Hensen bodies. 3) The Deiters' cell bodies were longer and this increased length was associated with the decreased length of the corresponding outer hair cells. Brainstem audiometry showed that DFMO produced a hearing loss and the magnitude of this loss increased over twelve weeks of DFMO administration.

Aminoglycosides↗

PubMed1994

[Hair cell damage and regeneration in the quail cochlea following kanamycin ototoxicity].

Forty-day old quails were given kanamycin (KM) at a dose of 400mg/kg per day for ten days. Evoked potential thresholds induced by both click and tone burst were obtained at 1 day or 1, 2, 3, 4 and 6 weeks respectively after the last injection, and compared with the thresholds of age-matched control animals. The cochlea of the animals was examined by scanning electron microscopy (SEM). The results showed that the application of KM for 10 days produced massive destruction of the basilar papilla at 1 day posttreatment. The damaged region began at the base and extended apically to the position about 50-70% of the total distance along the papilla, with most severe damage in the basal end. The auditory thresholds measured at the same time revealed a significant elevation at 2 and 4 kHz. However, the number of hair cells in the damaged region recovered rapidly with time, and so did the function. By the end of 3 weeks postinjection, almost all the hair cells reappeared in the pathologic region and the function improved further, with nearly normal thresholds at all frequencies but 4kHz. Six weeks after KM treatment, the basilar papilla showed a nearly normal appearance, but there was no further functional improvement at 4kHz, with the threshold shift by 17.5 dB (P < 0.01). The results of the present study demonstrated that structural recovery was faster than functional one.

Animals↗

PubMed1989

Audiologic threshold monitoring of patients receiving ototoxic drugs. Preliminary report.

An effort was made to determine the efficacy of auditory threshold monitoring of patients receiving ototoxic drugs. Forty-four patients treated with either tobramycin or vancomycin for osteomyelitis were tested at the beginning of treatment, following treatment, and twice weekly during treatment when possible. All patients had renal function carefully monitored. Peak and trough drug levels were kept out of the toxic range throughout the study. In no patient did indisputable ototoxicity occur, and therefore, no conclusion about the most efficacious schedule for auditory monitoring of patients receiving ototoxic drugs was made, and what constitutes a significant intratherapeutic threshold shift is still in question. Until further data are collected, monitoring of renal function and peak and trough drug levels, as well as patient counseling, is recommended. Pretherapy and posttherapy auditory monitoring and intratherapeutic monitoring of high-risk patients and those who develop aural symptoms may prove beneficial.

Adolescent↗

PubMedDate not supplied

Electrophysiological studies of the auditory system.

Electrophysiological measures of cochlear function can be obtained using the techniques of transtympanic electrode and surface electrocochleography. These provide measures of the basic parameters of the cochlear microphonic, cochlear nerve and auditory brainstem nuclei action potentials, which enable the functional mechanisms of the cochlea and auditory pathway to be defined for normally hearing subjects and, by comparison, give diagnostic information about the pathologies involved in auditory disorders. Data are presented on the values and variability of the responses obtained from normally hearing subjects. The comparative values of each technique in estimating auditory threshold, cochlear function and in evaluating neurological conditions are discussed using data from clinical patients.

Acoustic Stimulation↗

PubMed1978

Asymptotic threshold shift in chinchillas exposed to impulse noise.

Five monaural chinchillas were exposed to a repetitive, reverberant, impulse noise for ten days. The impulse-noise source was a mechanized hammer hitting a steel plate at a rate of 1/s. The average, peak over pressure within the holding cage was 113 dB SPL. Auditory thresholds were determined before and after exposure at 0.5, 1, 1.4 2, 2.8, 4, 8, and 16 kHz utilizing shock-avoidance conditioning. During exposure thresholds were monitored on a daily basis at 0.5 and 8 kHz. Within one hour from the start of the exposure, threshold shift at 8 kHz had reached an asymptotic level, while threshold shift at 0.5 kHz leveled off after 24 h of exposure. Asymptotic threshold shift (ATS) levels of both frequencies varied between 30 and 50 dB across animals. Median threshold shift for both frequencies recovered to within 10 dB of normal after 40 days of recovery. Maximum permanent threshold shift (PTS) was at 2 and 2.8 KHZ with median PTS of 17 and 13 dB, respectively. After final thresholds were obtained (50-70 days), the cochleas were examined histologically using the surface preparation technique. A comparison is made between impulse-noise-induced ATS and ATS produced by continuous-noise sources.

Acoustic Stimulation↗

PubMed1981

Relations between auditory functions in normal hearing.

The relations among a number of auditory functions were studied by concentration on small interindividual differences in these functions. For this purpose a battery of 12 tests was applied to 50 normal-hearing subjects. The tests included absolute threshold, auditory bandwidth measured with comb-filtered noise in direct and in forward masking, psychophysical tuning curve both in direct and in forward masking, temporal integration measured with intensity-modulated noise, forward- and backward-masking curves, cubic-difference-tone strength, and lateral suppression. In all cases the test frequency was 1000 Hz. Among the relations found, are (1) a positive correlation between the shift of the steep edge of the tuning curve, away from the probe frequency, and the width of the auditory filter as measured with comb-filtered noise, (2) an inverse relation between the width of the tuning curve and the width of the temporal window, and (3) a positive correlation between the width of the auditory filter and the strength of the cubic difference tone. Low correlations among tests were not caused by poor test reliability.

Acoustic Stimulation↗

PubMed1988

Frequency specific susceptibility to acoustic trauma in the budgerigar (Melopsittacus undulatus).

The effects of intense noise exposure on hearing in the budgerigar were examined by behavioral audiometry. After binaural exposure to an intense broadband noise, auditory threshold shifts (TS) of the birds were continuously measured at frequencies between 0.125 and 8 kHz using an avoidance conditioning technique. Temporary threshold shifts (TTS) were observed at frequencies higher than 1.5 kHz and considerable permanent threshold shifts (PTS) were observed at frequencies below 1 kHz. This pattern of threshold shifts is contrary to that observed in mammals.

Acoustic Stimulation↗