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PubMedDate not supplied

Acoustic echoplanar scanner noise and pure tone hearing thresholds: the effects of sequence repetition times and acoustic noise rates.

PURPOSE: Our goal was to determine the effects of acoustic echoplanar scanner noise on pure tone hearing thresholds in normal volunteers and to determine the influence of echoplanar sequence repetition time on threshold effects. METHOD: With use of a calibrated audiometer, pure tones ranging from 125 to 8,000 Hz were delivered monaurally to 10 normal-hearing volunteers in a quiet MR scanner suite and in the presence of acoustic scanner noise produced by three separate single shot blipped echoplanar pulse sequences varying only in repetition time (TR = 1,000, 2,000, or 3,000 ms), with all other parameters including the number of slices held constant. The magnitude of noise-induced threshold changes and the slopes of the threshold curves produced by each of the three echoplanar pulse sequences were then analyzed using multiple comparisons and a least significant difference method. The shapes of the threshold curves produced in each background state were best fit using a quadratic effect for frequency in a mixed effects linear model and compared using F test statistics. RESULTS: All of the volunteers demonstrated entirely normal hearing thresholds throughout the full range of tonal frequencies tested (< 25 dB) when no acoustic scanner noise was present in the scanner suite. Pure tone hearing thresholds significantly increased (p < 0.01) in the presence of acoustic scanner noise, with the magnitude of change inversely proportional to the repetition time and therefore the rate of periodic noise production by the echoplanar sequence used. The shape of the threshold curve in the presence of noise produced by the 1,000 ms TR sequence was not equivalent across the frequency spectrum tested but had a quadratic distribution with peak effects at 750-2,000 Hz. As the repetition time was increased and the periodic noise rate decreased, the magnitude of the noise-induced threshold changes significantly lessened (p < 0.01) and the quadratic distributions of the threshold curves changed significantly (p < 0.01), tending toward a more planar configuration. CONCLUSION: Background acoustic echoplanar scanner noise can significantly increase pure tone thresholds in the optimal frequency hearing range (125-8,000 Hz). However, the threshold effects are not equivalent across the frequency spectrum, and the magnitude of threshold changes is dependent on the rate at which periodic acoustic scanner noises are produced for a given sequence repetition time.

Acoustic Stimulation↗
PubMed2006

Characterizing acoustic attenuation of homogeneous media using focused impulsive acoustic radiation force.

A new method to characterize a material's attenuation using acoustic radiation force is proposed. Comparison of displacement magnitudes generated in a homogeneous material by acoustic radiation force excitations can be used to estimate the material's attenuation when the excitations are applied over a range of focal depths while maintaining a constant lateral focal configuration. Acoustic attenuations are related to the inverse of the excitation focal depth that yields the greatest focal zone displacement for this protocol. Experimental studies in calibrated tissue-mimicking phantoms are presented to demonstrate the feasibility of this method. Attenuations ranging from 0.3-1.5 dB/cm/MHz were characterized over excitation focal depths ranging from 5-30 mm, with an accuracy of 0.1 +/- 0.15 dB/cm/MHz. As currently implemented, this method is limited to characterizing materials that have homogeneous material properties and acoustic attenuations. This method for characterizing acoustic attenuation can be performed using conventional diagnostic scanners without any additional hardware and could also be performed concurrently with acoustic radiation force-based imaging modalities to generate images of mechanical properties and attenuation that are spatially co-registered with B-mode images.

Acoustics↗
PubMed1987

Acoustic (loudspeaker) facial EMG monitoring: II. Use of evoked EMG activity during acoustic neuroma resection.

Facial electromyographic (EMG) activity was continuously monitored via loudspeaker during eleven translabyrinthine and nine suboccipital consecutive unselected acoustic neuroma resections. Ipsilateral facial EMG activity was synchronously recorded on the audio channels of operative videotapes, which were retrospectively reviewed in order to allow detailed evaluation of the potential benefit of various acoustic EMG patterns in the performance of specific aspects of acoustic neuroma resection. The use of evoked facial EMG activity was classified and described. Direct local mechanical (surgical) stimulation and direct electrical stimulation were of benefit in the localization and/or delineation of the facial nerve contour. Burst and train acoustic patterns of EMG activity appeared to indicate surgical trauma to the facial nerve that would not have been appreciated otherwise. Early results of postoperative facial function of monitored patients are presented, and the possible value of burst and train acoustic EMG activity patterns in the intraoperative assessment of facial nerve function is discussed. Acoustic facial EMG monitoring appears to provide a potentially powerful surgical tool for delineation of the facial nerve contour, the ongoing use of which may lead to continued improvement in facial nerve function preservation through modification of dissection strategy.

Adult↗
PubMed2003

Clinical results with the acoustic puncture assist device, a new acoustic device to identify the epidural space.

UNLABELLED: Sixty patients scheduled for lumbar epidural anesthesia were included in a study in which we evaluated the efficacy of localizing the epidural space by means of an acoustic signal. A prototype of an acoustic puncture assist device, connected to the epidural needle by an extension tube, generated the pressure needed to perform the epidural puncture and translated this pressure into corresponding acoustic and visible signals. The device frees the anesthesiologist to handle the epidural needle with both hands and to detect the epidural space by means of these signals. In all 60 patients (100%), the epidural space was successfully located by using the acoustic signal. In all cases, this was confirmed by the pressure measurement, which proved to be a reliable indicator for correct identification of the epidural space. We conclude that it is possible to locate the epidural space by means of the acoustic puncture assist device. The method proved to be reliable, safe, and simple in this study. The benefits of this new epidural puncture technique include better needle control, teaching, control of correct catheter placement, and documentation. The last can be an important adjunct to anesthesia practice. IMPLICATIONS: The authors demonstrate that it is possible to identify the epidural space by an acoustic and visible signal. An experimental setup constructed for this purpose makes the epidural puncture procedure audible and visible.

Acoustic Stimulation↗
PubMed1985

MR imaging of the acoustic nerves and small acoustic neuromas at 0.6 T: prospective study.

To evaluate the capability of magnetic resonance (MR) in imaging normal acoustic nerves, 12 volunteers without signs or symptoms of intracranial disease were examined using a 0.6 T superconductive system. Several spin-echo (SE) pulse sequences were tested to identify the optimal sequence for demonstration of the acoustic nerve bundle. Repetition times (TRs) varied from 300 to 2000 msec and echo times (TEs) from 30 to 120 msec. A single-slice technique was used with 5 and 8 mm sections, one or two data acquisitions per projection, and axial and coronal imaging. The normal acoustic nerves were demonstrated readily by MR in axial and/or coronal sections. The distal parts of the nerves and tumors were imaged best with SE 1500/60. The medial extremities of the seventh and eighth nerves tended to be obscured in this sequence by brightening the cerebrospinal fluid signal adjacent to the brainstem, but they were demonstrated clearly with 500 or 800 msec TR and 30 msec TE. Five patients were studied who had hearing loss and evidence of retrocochlear disease. In four patients, MR imaging demonstrated five acoustic nerve tumors ranging in size from purely intracanalicular to a 12 mm cisternal component. In the fifth case, no tumor was identified by MR imaging or gas computed tomographic (CT) cisternography. Contrast-enhanced CT using a Siemens Somatom DR 3 or GE CT/T 8800 scanner failed to provide convincing evidence of tumor in any case, while gas CT cisternography was positive in all five tumors. All five acoustic neuromas were identified readily using the SE sequences that proved optimal for demonstration of normal nerves. This experience revealed that MR imaging can demonstrate the eighth nerve complex well and reliably. Single-slice (5 or 8 mm) technique is adequate, but multislice without tissue gaps (used recently) is more efficient. Small, even intracanalicular, acoustic neuromas are imaged effectively, indicating that the method is capable of superseding contrast CT cisternography, particularly with improving technology.

Atrophy↗
PubMed1990

Influence of acoustic deprivation on recovery of hair cells after acoustic trauma.

The purpose of this study was to investigate how the recovery of the cochlea, after acoustic trauma, might be influenced by acoustic stimulation or deprivation. In anaesthetized adult chinchillas, both ears were simultaneously exposed to a traumatizing acoustic stimulus (2 kHz tone, at 117 dB SPL for 15 min). Probe microphones positioned in both bullae were used to ensure identical exposure to the two ears; this was important because the experiment relies on within-animal controls. Cochlear action potential thresholds across frequency (CAP audiograms) were used to verify the similarity of threshold shifts to the two ears. Immediately following, a unilateral ossiculectomy was performed which resulted in one cochlea being acoustically deprived during the recovery period, whilst the other was not. In groups of animals with recovery periods of 1, 3, 6, and 12 weeks, both the acoustically deprived and the normally stimulated cochleas were examined with scanning electron microscopy. To quantify hair cell damage, we used a damage scale based on stereociliar integrity; for each cochlea, a standard region 5.5-8.5 mm from the apex was studied in detail. We found that after acoustic trauma, hair cell damage to the cochlea which is deprived of sound during the recovery period, is significantly greater compared with that in the normally stimulated, contra-lateral cochlea. Our results suggest that mechanical activation of the inner ear acts to inhibit long-term degenerative processes, or influence repair of partially damaged hair cells.

Action Potentials↗
PubMed2004

Picosecond acoustic transmission measurements. I. Transient grating generation and detection of acoustic responses in thin metal films.

The technique of impulsive stimulated thermal scattering is extended to backside measurement of acoustic wave packets that have propagated through thin metal films following their generation by pulsed optical excitation, heating, and thermal expansion at the front side. The acoustic transmission measurement at the backside substantially isolates the acoustic responses from thermal and electronic responses of the metal film that often dominate acoustic reflection signals measured from the front side, and permits straightforward measurement of the acoustic response generated by optical excitation at a substrate-thin film interface. It can thus better distinguish among different factors that limit the bandwidth of the acoustic wave packet, an issue of concern in the measurement of high frequency responses. The paper that follows demonstrates the application of the backside measurement to a study of high frequency structural relaxation in the glass-forming liquid glycerol.

Journal Article↗
PubMed1989

Effects of alcohol on the acoustic-phonetic properties of speech: perceptual and acoustic analyses.

This report summarizes the results of a series of studies that examined the effects of alcohol on the acoustic-phonetic properties of speech. Audio recordings were made of male talkers producing lists of sentences under a sober condition and an intoxicated condition. These speech samples were then subjected to perceptual and acoustic analyses. In one perceptual experiment, listeners heard matched pairs of sentences from four talkers and were required to identify the sentence that was produced while the talker was intoxicated. In a second perceptual experiment, Indiana State Troopers and college undergraduates were required to judge whether individual sentences presented in isolation were produced in a sober or an intoxicated condition. The results of the perceptual experiments indicated that groups of listeners can significantly discriminate between speech samples produced under sober and intoxicated conditions. For acoustic analyses, digital signal processing techniques were used to measure acoustic-phonetic changes that took place in speech production when the talker was intoxicated. The results of the acoustical analyses revealed consistent and well-defined changes in speech articulation between sober and intoxicated conditions. Because speech production requires fine motor control and timing of the articulators, it may be possible to use acoustic-phonetic measures as sensitive indices of sensory-motor impairment due to alcohol consumption.

Adult↗
PubMed2003

A state feedback electro-acoustic transducer for active control of acoustic impedance.

In this paper, a new control system in which the acoustic impedance of an electro-acoustic transducer diaphragm can be actively varied by modifying design parameters is presented and its effectiveness is theoretically investigated. The proposed control system is based on a state-space description of the control system derived from an electrical equivalent circuit of an electro-acoustic transducer to which a differentiating circuit is connected, and is designed using modem control theory. The optimal quadratic regulator is used in the control system design, with its quadratic performance index formulated for producing desired acoustic impedance. Computer simulations indicate that the acoustic impedance of the diaphragm can be significantly varied over a wide frequency range that includes the range below the resonance frequency of the electro-acoustic transducer. A computer model of the proposed control system is used to illustrate its application to semi-active noise control in a duct. It is demonstrated that the proposed control system provides substantial reductions in the noise radiating from the outlet of the duct, both in the stiffness control range and in the mass control range.

Journal Article↗
PubMed2000

Effects of acoustic trauma on acoustic enhancement of electrically evoked otoacoustic emissions.

Moderate acoustic trauma results in decreased cochlear sensitivity and frequency selectivity. This decrease is believed to be caused by damage to the cochlear amplifier that is associated with outer hair cells (OHCs) and their nonlinear electromechanical characteristics. A consequence of OHC nonlinearity is the acoustic enhancement effect, in which low-frequency electrically evoked otoacoustic emissions are enhanced by a simultaneous tone. The present study found that acoustic trauma reduced the acoustic enhancement effect and this reduction is correlated with the N1 threshold at the electrode site. This result is consistent with the theory that trauma affects the mechanoelectric transduction process, thus affecting cochlear mechanical nonlinearity. Acoustic trauma also reduced the cochlear microphonic in a way that suggests that the number of functioning tension-gated channels and the stiffness of the gating springs were decreased. In some cases, the electromechanical transduction process was also found to be affected by acoustic trauma.

Animals↗
PubMed1994

The acoustic properties of normal and imbedded bovine bone as measured by acoustic microscopy.

The acoustic impedance of bovine femoral cortical bone was measured with a scanning acoustic microscope used in the reflection mode. The bone was measured in the unimbedded state and after plastic imbedding. The acoustic impedance of the unimbedded specimens was also measured with a standard transmission ultrasonic technique. For the unimbedded bovine specimens there was a good correlation between the bulk transmission impedance and the reflection surface impedance (r2 = 0.976) and the values were 9.32 and 9.29 MRayls, respectively. Plastic imbedding produced a consistent and statistically significant increase in the acoustic impedance of the bone (9.71 MRayls). This experiment verified the use of acoustic microscopy as a quantitative materials analysis technique and it demonstrated the potential for material property analysis of imbedded bone.

Acoustic Impedance Tests↗
PubMed1995

Changes in the acoustic startle response and prepulse inhibition of acoustic startle in rats after local injection of pertussis toxin into the ventral tegmental area.

The effect of local injection of pertussis toxin (PTX) into the ventral tegmental area (VTA) on acoustic startle in rats was investigated. The PTX treatment caused only minor effects of its own on the acoustic startle response (ASR) or prepulse inhibition (PPI) of acoustic startle. However, systemic treatment with the indirect DA receptor agonist, amphetamine (2 mg/kg, SC) caused a significant increase in ASR magnitude and a significant disruption of PPI in PTX-treated rats while no such effects were observed in sham-treated rats. Treatment with the direct DA receptor agonist, apomorphine (2 mg/kg, SC), caused a significant disruption of PPI, an effect that was observed in both PTX- and sham-treated rats. Treatment with the 5-HT1A receptor agonist, 8-OH-DPAT (0.5 mg/kg, SC), did not affect PPI in either group but caused a marked increase in ASR magnitude in sham-treated rats. Interestingly, this effect was blocked in PTX-treated rats. The present results suggest that local injection of PTX into the VTA causes an increased sensitivity to the behavioural effects of psychostimulants on acoustic startle and may also suggest that intact midbrain 5-HT1A receptors are essential for the effect of 5-HT1A agonists on acoustic startle.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

Evaluation of acoustic properties of the live human smooth-muscle cell using scanning acoustic microscopy.

This study was performed to measure the acoustic propagation speed in live human aortic smooth-muscle cells (HASMC), using scanning acoustic microscopy (SAM) and a novel measurement theory that permits the measurement of the acoustic propagation speed in biological samples of unknown thickness. C-mode and X-Z-mode images of HASMC under three different conditions: growing (G); differential (D); and on hypotonic loading (H), were acquired using 100-MHz, 450-MHz and 600-MHz ultrasound. The images exhibit features related to the cell surface curvature and intracellular structure. The theory supporting the methodology is derived in this article and makes use of the interference fringes within the focusing lens of the high-frequency transducer. The propagation speed in the cells was calculated from the location of the interference fringe on the C-mode images and the fringe shift on the X-Y-mode images with 450-MHz ultrasound. The propagation speed in D (1624 +/- 16 m/s) was significantly higher than those in G (1571 +/- 14 m/s, p < 0.05) and H (1585 +/- 8 m/s, p < 0.05). Scanning acoustic microscope measurements, along with the described theory, are useful for studying the acoustic properties of live cells ex vivo and have applications in both pathophysiology and biomechanics.

Acoustics↗
PubMed2002

Acoustic phenotypes for speech-genetics studies: toward an acoustic marker for residual /s/ distortions.

Findings in a prior study series indicate that acoustic markers may have the requisite sensitivity and specificity to discriminate speakers with histories of several types of speech disorders, one of which is posited to be genetically inherited. The present study in this series compares acoustic data from three groups of adolescent speakers. Group 1 speakers had residual dentalized /s/ distortions in conversational speech and histories of significant age-inappropriate deletion and substitution errors. Group 2 speakers also had residual dentalized /s/ distortions in conversational speech, but their speech histories were limited to dentalized distortions of /s/ and other fricatives/affricates. Group 3 speakers had typical speech on assessment and no histories of speech errors. Owing to the limited number of perceptually dentalized /s/ tokens produced by Groups 1 and 2 speakers in a phrase-level speech task, acoustic analyses were completed on /s/ tokens transcribed as correct for speakers in all groups. Moments analyses of /s/ spectra in three words with /s/-initial clusters yielded statistically significant differences and consistent trends for mean spectral frequency and spectral variance for Group 1 compared with Group 2 speakers. These findings for perceptually normal /s/ tokens are interpreted as additional support for the potential of acoustic markers to discriminate speakers' speech-error histories. The discussion considers possible developmental and normalization correlates of the acoustic findings for speakers with each of the two types of speech-error histories studied in this paper.

Adolescent↗
PubMed1989

Acoustic rhinometry: evaluation of nasal cavity geometry by acoustic reflection.

To study the geometry of the nasal cavity we applied an acoustic method (J. Appl. Physiol. 43: 523-536, 1977) providing an estimate of cross-sectional area as a function of distance. Acoustic areas in a model constructed from a human nasal cast, in the nasal cavity of a cadaver and in 10 normal subjects and two patients with well-defined afflictions of the nasal cavity, were compared with similar areas obtained by computerized tomography (CT) scans, a specially developed water displacement method, and anterior rhinomanometry. We found a coefficient of variation of the areas of less than 2% by the acoustic method compared with 15% for the rhinomanometric measurements. Acoustic areas correlated highly to similar areas obtained by CT scanning (r = 0.94) and by water displacement (r = 0.96). In two patients the acoustic method accurately outlined, respectively, a tumor in the nose and a septum deviation. It is concluded that this method provides an accurate method for measuring the geometry of the nasal cavity. It is easy to perform and is potentially useful for investigation of physiological and pathological changes in the nose.

Acoustics↗
PubMedDate not supplied

[Acoustically guided behavior in the early ontogeny of the long-eared owl: the characteristics of its feeding behavior and the parameters of the acoustic signal important for its stimulation].

Feeding behaviour of nestlings of long-eared owls (Asio otus) is manifested as a complex of two components, i. e., the vocal reaction (uttering of begging calls) and specific motor response. Exposure to the appropriate acoustic signals resulted in an increase in the number of begging calls and approaching reaction to the source of acoustic signals. The range of monotonal signals effective for eliciting feeding behaviour was 0.2--1.5 kHz, the most effective were the tones of 0.3--0.7 kHz. The approaching reaction to acoustic signals was rather weak up to the 5th day after hatching, clearly pronounced in the 6--11th days, and later on was abruptly substituted for the response of following the visual stimulus provoked by the acoustic stimulation. Specific acoustic afferentation is the sole stimulus for begging in nestlings up to 11 days of age, and it remains a triggering stimulus for feeding behaviour in owl nestlings throughout the period of artificial feeding under laboratory conditions (up to the 40th day after hatching.

Acoustic Stimulation↗
PubMed1979

Factors influencing the acoustic-immittance characteristics of the acoustic reflex.

Measurements of the aural acoustic-immittance (admittance and impedance) characteristics of the middle-ear transmission system in humans during the quiescent (static) and reflexive states were made (N = 36) utilizing a signal-averaging technique. Three pure tones (750, 1000, and 2000 Hz) and broadband noise stimuli elicited the acoustic reflex in 2-dB steps at sound-pressure levels from 84-116 dB (tones) and 66-116 dB (noise) during ascending- and descending-intensity level runs. The contralateral middle-ear activity was monitored with a 220-Hz probe by digitizing the conductance and susceptance outputs of an admittance meter. A computer corrected for the ear-canal volume utilizing measurements made at ear-canal pressures of 0 and --350 daPa and then converted the conductance and susceptance values into admittance and impedance units. The results were reported in absolute and relative immittance units, including components, as a function of both stimulus sound-pressure level and intensity level above the acoustic-reflex threshold. The static immittance of the middle ear changed nonlinearly over time to lower admittance or higher impedance values. The influence of this static-immittance shift on the reflex magnitude was discussed. The largest mean reflex magnitude and the slowest rate of growth were observed with broadband noise, although eight of the 36 subjects demonstrated the largest reflex magnitude in response to one or more of the tonal stimuli. Although static-immittance values and acoustic-reflex thresholds were poorly correlated, the reflex magnitudes were proportional to static immittance. The variability of the reflex measures was similar to the variability of the static-immittance values. Finally, bi-directional changes in resistance during the reflexive state were observed and discussed.

Acoustic Impedance Tests↗