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PubMed1992

Acoustic-immittance screening for detection of middle-ear effusion in children.

The purpose of this investigation was to evaluate the sensitivity and specificity of the following acoustic-immittance protocols and their constituent measures for detection of middle-ear effusion in children: (a) tympanometric width; (b) absent ipsilateral acoustic reflex; (c) ASHA guidelines; (d) tympanometric peak pressure; and (e) static-acoustic middle-ear admittance. The middle-ear sample was composed of 82 ears of 54 subjects ranging in age from 3 to 11 years. The control (normal-hearing, normal middle-ear) sample was composed of 53 ears of 53 subjects ranging in age from 3 to 10 years. Each subject was given a complete otolaryngologic evaluation (including pneumotoscopy and/or microtoscopy) and audiologic (including acoustic-immittance) evaluation. In the group of middle ears with normal-hearing sensitivity, the sensitivity and specificity of the ASHA guidelines were 63 percent and 79 percent, respectively. An acoustic-immittance screening protocol, based on all of the individual acoustic-immittance measures, and characterized by high sensitivity and specificity, is proposed.

Acoustic Impedance Tests↗
PubMed2001

The sensitivity of auditory brainstem response testing for the diagnosis of acoustic neuromas.

OBJECTIVES: To determine the sensitivity of auditory brainstem response (ABR) testing for detecting acoustic neuromas and to determine whether the test is less sensitive for detecting small tumors. DESIGN: Retrospective review of the medical charts of 58 patients with acoustic neuroma who had all of the data necessary for inclusion in the study. SETTING: University-affiliated referral practice of one neurotologist. PATIENTS: Patients with acoustic neuromas who had both ABR tracings and magnetic resonance imaging films available for review. MAIN OUTCOME MEASURES: Positive ABR and negative ABR results correlated with tumor size. RESULTS: Tumor size ranged from 0.4 to 7 cm. The overall sensitivity of ABR in diagnosing acoustic neuromas was 90%. However, ABR was progressively less sensitive with decreasing tumor size. Only 7 (58%) of the 12 tumors 1 cm or smaller were detected by ABR. CONCLUSION: Auditory brainstem response testing cannot be relied on for detection of small acoustic neuromas and should not be used as a criterion to determine whether magnetic resonance imaging should be performed when an acoustic neuroma is suspected clinically.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1999

Investigations on acoustic on-line monitoring of IR laser ablation of burned skin.

BACKGROUND AND OBJECTIVE: In burn surgery necrotic tissue has to be removed prior to grafting. Tangential excision causes high blood loss and destruction of viable tissue. Pulsed infrared laser ablation can overcome both problems because of its high precision and the superficial coagulation of the remaining tissue. We investigated the ablation noise to realize an acoustic feedback system for a selective removal of necrotic tissue. MATERIALS AND METHODS: We studied free-running Er:YAG laser ablation of gelatin and burned skin. Schlieren laser flash photography was used to investigate the ablation dynamics generating the ablation noise. Acoustic signals were detected by a condenser microphone and a piezoelectric airborne transducer. Tissue discrimination was based on the evaluation of the normalized acoustic energy. RESULTS: The ablation noise is mainly generated by shock wave emission and fast vaporization during the first part of the laser pulse. Frequency components of the ablation noise above 200 kHz are only detectable with the piezoelectric transducer. The normalized acoustic energy differs significantly between gelatin samples of different water content and between necrotic and vital tissue. CONCLUSIONS: Large bandwidth transducers are essential for an acoustic on-line monitoring of free-running Er:YAG laser ablation of burned skin. The normalized acoustic energy is a suitable parameter for the discrimination between necrotic and vital tissue.

Acoustics↗
PubMed1990

Theory of acoustic mode vibrations of DNA fibers.

A previous model for acoustic mode vibrations of a DNA molecule in water is extended to the case of an array of many DNA molecules, as occurs in the fibers studied in most experimental work on DNA. The acoustic modes of this system are found to consist of coupled modes of water sound vibrations and DNA acoustic modes. This model is used to study the electrostatic coupling of acoustic vibrations to the relaxational modes of the orientational degrees of freedom of the water molecules. It is found that the long-range or macroscopic electric field generated by the acoustic mode vibrations of the water-DNA system gives too small a damping and frequency shift of the acoustic modes to account for the observations on DNA fibers. Therefore, the observed damping and frequency shifts are most likely due to either friction between the surrounding water and the vibrating DNA, or coupling to the water orientation degrees of freedom resulting from the short range (i.e., screened) Coulomb interaction. The latter explanation (which is most likely the correct one) implies that the relaxation time of the hydration shell water is longer than the observed relaxation time by a factor of the static dielectric constant of the hydration water.

Acoustics↗
PubMed1989

Acoustic and plasma-guided laser angioplasty.

The feasibility of using acoustic and plasma-guided laser (APGL) for angioplasty was studied in vitro. A flashlamp-pumped tunable dye laser operating at a wavelength of 504 nm (coumarin green) was used as the laser source. Acoustic signals were recorded with a hydrophone, which has a useful frequency response of up to 350 kHz. Plasma optical emissions were transmitted retrograde along the laser fiber and reflected through a beam splitter to an optical detection system consisting of a series of spectral filters (to transmit plasma radiation from 380 nm to 440 nm and block any 504 nm laser light) and a photomultiplier tube. Measurements of the acoustic and the plasma optical signals were obtained from blood, atheromatous plaque, and normal arterial wall. Results of monitoring show that it is possible to know without direct vision whether the laser energy is being discharged in the lumen (blood), on the normal arterial wall, or on the atheromatous plaque. Blood produced strong acoustic signals but no plasma signals; plaque produced strong plasma and strong acoustic signals. Neither plasma nor significant acoustic signals were produced by the normal arterial wall. These distinctions may allow clinical laser ablation of plaque to be performed with fewer complications.

Acoustics↗
PubMed2003

Optimized gradient pulse for use with EPI employing active acoustic control.

The concept of active acoustic control was recently introduced by Mansfield and Haywood (MAGMA 2000:10:147-151) to ameliorate the problem of acoustic noise from MRI, particularly that from high-speed EPI. A 30 dB reduction in noise was previously achieved with the use of acoustic control operating at spot frequencies within a narrow band. In this work, a new acoustic gradient pulse is introduced that comprises an oscillating gradient of finite duration, incorporating a combination of frequencies within this band designed for use as the switched read gradient in echo-planar imaging (EPI). Employing this pulse with active acoustic control results in a reduction of acoustic noise by 50 dB.

Acoustics↗
PubMed2001

Active acoustic control in gradient coils for MRI.

The new principles of active acoustic control in gradient coil design recently introduced by Mansfield and Haywood (MAGMA 1999;8(Suppl 1):55) are further developed theoretically for the far-field acoustic output for a single sector of a coil system comprising four or more flat rectangular coil sectors. Each sector consists of a split plate arrangement in which are embedded two windings, an outer primary winding and a narrow inner re-entrant loop control winding immediately adjacent to and surrounding the split or air gap. The wire spacing of the control winding is made small so as not to affect substantially the magnetic field created by the primary winding. Experimental results are presented for two sectors each made of a different readily available plastic material and tested over a range of frequencies. They both show substantial average reductions in acoustic output over the full output when the control winding is appropriately driven. New theoretical expressions are derived for particular frequencies based on normal mode expansions for the plate. This new approach is better able to explain the acoustic output difference between the full and reduced output modes. Empirical expressions are also developed which include longitudinal as well as transverse plate characteristics and used to fit the experimental acoustic output data as a function of frequency and indicate good agreement with regard to both the form and amplitude of the acoustic output response.

Acoustics↗
PubMed2005

Extraction of overt verbal response from the acoustic noise in a functional magnetic resonance imaging scan by use of segmented active noise cancellation.

A method to extract the subject's overt verbal response from the obscuring acoustic noise in an fMRI scan is developed by applying active noise cancellation with a conventional MRI microphone. Since the EPI scanning and its accompanying acoustic noise in fMRI are repetitive, the acoustic noise in one time segment was used as a reference noise in suppressing the acoustic noise in subsequent segments. However, the acoustic noise from the scanner was affected by the subject's movements, so the reference noise was adaptively adjusted as the scanner's acoustic properties varied in time. This method was successfully applied to a cognitive fMRI experiment with overt verbal responses.

Acoustics↗
PubMed2005

Acoustic arousal responses in children with obstructive sleep apnea.

Our objectives were to study the arousal responses to nonrespiratory (acoustic) stimuli in children with obstructive sleep apnea syndrome (OSAS). The acoustic arousal response was studied in children with OSAS due to adenotonsillar hypertrophy compared to normal, age-matched children. Acoustic stimuli were delivered incrementally from 30-100 dB during stage 2, slow wave sleep, and rapid eye movement (REM) sleep. The percentage of children who aroused in response to acoustic stimuli, and the arousal threshold (i.e., sound level at which arousal occurred), were compared between groups and sleep stages. The percentage of children who aroused was similar between children with OSAS and controls. The percentage of children who aroused was lower during slow wave sleep than REM sleep and stage 2 in both OSAS and controls. There were no statistically significant differences in acoustic arousal threshold between OSAS and control children. There was no difference in arousal response to moderate acoustic stimulation between children with OSAS and controls. These results contrast with previous data showing blunted arousal responses to hypercapnia and upper airway loading during sleep in children with OSAS, suggesting that children with OSAS have an arousal deficit specific to respiratory stimuli. However, further studies evaluating arousal to both respiratory and nonrespiratory stimuli in the same subjects are needed.

Acoustic Stimulation↗
PubMed1990

The influence of the auditory cortex on acoustically evoked cerebellar responses in the CF-FM bat, Rhinolophus pearsonic chinesis.

1. Acoustically evoked responses of 284 neurons isolated from the cerebellar vermis, hemispheres and paraflocculus of Rhinolophus pearsonic chinesis were studied under free field acoustic stimulation conditions. 2. The BFs of these cerebellar auditory neurons ranged from 24 to 76 kHz but they mostly fall either between 48 and 64 kHz or between 65 and 76 kHz. However, the BF distribution varies among vermal, hemispheric and parafloccular neurons. 3. Threshold curves of cerebellar neurons are generally broad but those tuned to the frequency of the predominant CF component are extremely narrow. 4. Response latencies of cerebellar neurons ranged from 2 to 48 ms suggesting multiple auditory cerebellar pathways. The latency distribution also varies among vermal, hemispheric and parafloccular neurons. 5. Although both the vermis and hemispheres contain a disproportionate number of 65-74 kHz neurons, the response latencies of those neurons isolated from the vermis are scattered over a wide range of 2.2-28 ms while those neurons isolated from the hemispheres are generally stabilized between 5 and 12 ms. 6. Electrical stimulation of the auditory cortex evokes discharges from a recorded cerebellar auditory neuron. Cortical stimulation also facilitates the response of an acoustically evoked cerebellar neuron by increasing its number of impulses. The degree of facilitation is dependent upon the amplitude of the acoustic stimulus. 7. For a given electrical and acoustic stimulation condition, the facilitative latency and the degree of facilitation varied with the interstimulus interval. Among 23 neurons studied, most of them (19 neurons, 82.6%) had a maximal facilitative latency between 2 and 10 ms. 8. By examining the difference in the facilitative effect in each isolated cerebellar auditory neuron before and after a topical application of local anesthetic, procaine, onto the point of electrical stimulation in the auditory cortex, we found that the facilitative pathways to vermal and hemispheric neurons may be different from the pathway to parafloccular neurons. 9. Possible auditory pathways to different parts of the cerebellum are discussed in relation to the wide range of recorded response latencies. 10. The facilitative influence of the auditory cortex on the cerebellar auditory neurons is assumed to enhance the cerebellar role in acoustic motor orientation.

Acoustic Stimulation↗
PubMed1985

Cocaine: effects on acoustic startle and startle elicited electrically from the cochlear nucleus.

Startle-like responses can be elicited by single pulse electrical stimulation of nuclei within the acoustic startle pathway. Compared with acoustically-elicited startle, this technique provides a method for localizing the ultimate sites of action of a drug that affects the acoustic startle response. Strychnine (1 mg/kg) increased both acoustically-elicited startle and startle elicited from the ventral cochlear nucleus (VCN), the first central nucleus in the acoustic startle pathway. In contrast, cocaine (10 mg/kg) increased acoustically-elicited startle but depressed VCN-elicited startle. These results suggest that cocaine increases startle by acting on sensory rather than final motor systems and are discussed in relation to the putative effect of cocaine on dopamine neurotransmission and the involvement of dopamine in sensorimotor reactivity.

Acoustic Stimulation↗
PubMed2002

The development and clinical application of acoustical technique in hip joint.

A non-invasive acoustical system was developed for the measurement of transmission properties of acoustic waves in the hip joints. The instrumentation consisted of three sub-systems. An excitation system employed a vibratory force at the sacrum of the test subjects. A transduction system included a pair of identical microphones installed in the tubes of two stethoscopes, which were placed at the greater trochanters on both sides for picking up the acoustical signals transmitted across the hip joints. The data acquisition and analysis system was a portable signal analyzer with a program of dual channel digital filter for measuring the power of acoustical signal in 1/3-octave frequency bands. 27 normal adults, 20 normal pre-school children and 40 normal neonates were randomly selected for testing. Coherence function (CF) and discrepancy (D) was measured during the testing. Results from the three groups showed that there was a high coherence of the signals (CF > 0.9) and a small discrepancy (D < 3 dB) between bilateral hips in the frequency range of 200-315 Hz. For normal neonates, there was a wider frequency range of 160-315 Hz in which the acoustical signals maintained a high coherence (CF > 0.93) and a smaller discrepancy (D < 2 dB) was observed. This study showed that the development of the acoustical technique provided a practical method with objective parameters. The results obtained in this study can offer a baseline for further investigation of hip disorders particularly those related to structural abnormalities of the hip.

Acoustic Stimulation↗
PubMed2000

The sounds of silence: cessation of singing and song pausing are ultrasound-induced acoustic startle behaviors in the katydid Neoconocephalus ensiger (Orthoptera; Tettigoniidae).

Previous studies of acoustic startle in insects have dealt with behavioral and/or neural mechanisms employed in evading aerially hawking, echolocating bats; however, insects also face terrestrial predators. Here we describe an acoustic startle response of the nocturnal katydid, Neoconocephalus ensiger. Stridulating males disturbed in the field perform obvious antipredatory behaviors--cessation of singing, freezing, jumping, and evasive flight. Under controlled laboratory conditions we found that cessation of singing and song pausing are ultrasound-specific behaviors: when stimulated with pulsed ultrasound (20-100 kHz), but not audio-sound (< 20 kHz), males cease mate calling or insert pauses in their song. A second factor influencing acoustic startle is the phase of stimulation: an acoustic startle response occurs only when the pulse of ultrasound arrives during the window of silence between stridulatory syllables. The average startle threshold and response latency was 70 +/- 5 dB SPL and 34.2 +/- 6.0 ms, respectively. N. ensiger is particularly useful for examining acoustic startle responses of nonflying insects because (1) its calling song is broadband and contains ultrasound, thus the possibility exists of confusion over the biological meaning of ultrasound, and (2) this species shows the classic bat-avoidance response while flying, so a direct comparison between two types of acoustic startle is possible within the same species.

Acoustic Stimulation↗
PubMed2002

Acoustic neuroma surgery and tinnitus.

The objectives of this study were to assess the effect that acoustic neuroma surgery has on tinnitus and to investigate possible predictors (tumour size and patients' ages at operation) as well as to ascertain if the overall quality of life in patients with acoustic neuromas is affected by their tinnitus. A questionnaire was sent to randomly selected patients post acoustic-neuroma surgery. This was based on the Glasgow Benefit Inventory and contained a standardised series of four functional gradings for tinnitus. In this study, 51 patients from a total of 68 returned the questionnaire, and there was a follow-up period of between 1 and 3 years following the acoustic neuroma surgery. The age at operation, size of the tumour and overall quality of life were correlated with the impact of surgery on tinnitus. Statistical analysis used the one-way analysis of variance, chi-square test, one-way analysis by ranks and Spearman Rank Correlations. Significance was accepted at the P<0.05 level. Overall, 30 (58.8%) of the patients had tinnitus preoperatively in comparison to 34 (66.6%) postoperatively. After surgery, tinnitus became better in 8 (16%) patients, 28 (55%) did not experience any change, and 15 (29%) became worse. Neither tumour size nor age at the time of the operation had a statistically significant association with the impact of surgery on tinnitus. There was no statistically significant association between changes in tinnitus status and changes in the quality of life following the operation ( P>0.05). A significant percentage of patients with acoustic neuromas, approximately 60%, suffer from tinnitus preoperatively, and this number may increase slightly postoperatively. It remains unpredictable which patients will improve, which will show no change and which will deteriorate as age and tumour size do not seem to be associated with the impact of surgery on tinnitus. The results also suggest that tinnitus may be of relatively minor importance in the overall quality of life of patients following acoustic neuroma surgery. However, candidates for surgery should be thoroughly informed about the possible effect of the operation on their tinnitus status.

Adult↗
PubMed1999

The role of acoustic rhinometry in the diagnosis of adenoidal hypertrophy in pre-school children.

UNLABELLED: Adenoidal hypertrophy is a common problem in pre-school children and diagnosis depends mostly on evaluation of clinical symptoms and signs. Investigative techniques to assess adenoidal size often do not add to this information. Recent reports have suggested a role for acoustic rhinometry in this situation. A total of 49 children consecutively referred to the Department of Otorhinolaryngology, University of Mainz, with evidence of adenoidal enlargement underwent acoustic rhinometry pre- and post-operatively and were compared to an age-matched control group from a local kindergarten school. Adenoidal size was visually estimated at surgery and questionnaires were completed by parents of symptomatic children. Acoustic rhinometry was not able to differentiate controls (mean nasopharyngeal cross-sectional area 1.34+/-0.47 cm2, n = 35) from symptomatic children admitted for adenoidectomy (mean nasopharyngeal cross-sectional area 1.66 +/- 0.83 cm2, n = 42, P = 0.53). Acoustic rhinometry was advantageous for patients with adenoidal hypertrophy in two situations. Firstly a sub-group of patients with complete nasopharyngeal obstruction could be identified (P = 0.03) and secondly all patients with a postnasal space less than 1.2 cm2 clinically benefited from adenoidectomy. CONCLUSIONS: Acoustic rhinometry, in general, is not suitable for assessing adenoidal size in pre-school children. Physical limitations of currently available acoustic rhinometers are likely to explain the limited clinical value of this investigative technique.

Acoustics↗
PubMed1989

The effects of vibratory acoustic stimulation on baseline fetal heart rate in term pregnancy.

Fetal heart rate responses to vibratory acoustic stimulation have been studied in normal and complicated pregnancies. To determine the precise nature of these responses, we studied 50 normal term fetuses with 60 minutes of electronic antepartum fetal heart rate monitoring divided in two 30-minute segments separated by 3 seconds of vibratory acoustic stimulation. All tracings were analyzed by a programmed microcomputer. Comparison of grouped mean 30-minute values before and after vibratory acoustic stimulation showed significant increases in baseline fetal heart rate, fetal heart rate variation, frequency of accelerations exceeding 10 and 15 beats/min, duration of accelerations exceeding 15 beats/min, and frequency of decelerations after vibratory acoustic stimulation. Mean baseline fetal heart rate elevation greater than 10 beats/min occurred within 7.6 +/- 4.4 seconds in 42 of 50 fetuses and lasted for 596 +/- 531 seconds. Reactive tests increased from 35 (70%) to 47 (94%) after vibratory acoustic stimulation. Most healthy term fetuses exhibit fetal heart rate responses after differing in frequency or magnitude from spontaneous fetal heart rate changes. Vibratory acoustic stimulation may be a valid fetal assessment tool but cannot be considered the physiologic equivalent of nonstress testing.

Acoustic Stimulation↗
PubMed1989

Electrical stimulation of bat superior colliculus influences responses of inferior collicular neurons to acoustic stimuli.

The influence of electrical stimulation of the superior colliculus (SC) on acoustically evoked responses of inferior collicular (IC) neurons was examined in 24 barbiturate-anesthetized Rufous horseshoe bats, Rhinolophus rouxi. Acoustic stimuli (50 ms, 0.5 ms rise-decay times) were delivered from a loudspeaker placed 68 cm in front of each bat and a total of 354 IC neurons were isolated. The response latencies of these neurons were mainly between 7.5 and 17.5 ms. When the ipsilateral SC was electrically stimulated, responses of 227 (64%) neurons were not affected, but responses of the remaining (127 neurons, 36%) were either inhibited (102 neurons, 29%) or facilitated (25 neurons, 7%). The degree of inhibition and the response latency of the inhibited neurons increased with the amplitude of electrical stimulation. Inhibition of a neuron's activity was also dependent upon the time interval between acoustic and electrical stimuli. The best inhibitory latency measured at maximal inhibition was between 12 and 20 ms. Conversely, facilitation shortened the response latency of IC neurons and the degree of facilitation increased with the amplitude of the acoustic stimulus. Since the SC plays an essential role in orienting an animal's responses toward sensory stimuli, our findings suggest that the SC may affect the processing of acoustic signals in the auditory system during acoustically guided orientation.

Acoustic Stimulation↗
PubMed1984

Sound pressure level measurement and spectral analysis of brief acoustic transients.

The sound pressure level (SPL) of an acoustic transient can be quantified in several ways. The SPL value obtained is dependent on measurement procedure, in addition to signal and transducer characteristics. The acoustic spectrum of a signal shows sound pressure as a function of frequency. The acoustic spectrum can be determined by the use of analog filtering or by Fourier transformation. A constant electrical signal can produce different acoustic spectra due to varying transfer functions across transducers. Signal center frequency, rise/fall time and plateau influence acoustic spectrum. Recording parameters, such as constant bandwidth versus logarithmic bandwidth filtering, or the time domain windowing function used prior to Fourier transformation, also influence the acoustic spectrum.

Acoustic Stimulation↗