Acoustic Tone Bursts Research Articles

Differential Activation of Canal and Otolith Afferents by Acoustic Tone Bursts in Rats.

Vestibular evoked myogenic potentials (VEMPs) are routinely used to test otolith function, but which specific vestibular afferent neurons and central circuits are activated by auditory frequency VEMP stimuli remains unclear. To examine this question, we analyzed the sensitivity of individual vestibular afferents in adult Sprague-Dawley rats to tone bursts delivered at 9 frequencies (125-4000Hz) and 3 intensity levels (60, 70, 80dB SL re: acoustic brainstem response (ABR) threshold). Afferent neuron tone sensitivity was quantified by the cumulative probability of evoking a spike (CPE). Based on a threshold CPE of 0.1, acoustic stimuli in the present study evoked responses in 78.2 % (390/499) of otolith afferent neurons vs. 48.4 % (431/891) of canal afferent neurons. Organ-specific vestibular inputs to the central nervous system in response to tone bursts differ based on intensity and frequency content of the stimulus. At frequencies below 500Hz, tone bursts primarily activated both otolith afferents, even at the highest intensity tested (80dB SL re ABR threshold). At 1500Hz, however, tone bursts activated the canal and otolith afferents at the moderate and high intensities tested (70, 80dB SL), but activated only otolith afferents at the low intensity tested (60dB SL). Within an end organ, diversity of sensitivity between individual afferent neurons correlated with spontaneous discharge rate and regularity. Examination of inner ear fluid mechanics in silico suggests that the frequency response and preferential activation of the otolith organs likely arise from inner ear fluid motion trapped near the oval and round windows. These results provide insight into understanding the mechanisms of sound activation of the vestibular system and developing novel discriminative VEMP testing protocols and interpretative guidelines in humans.

Comparison of Pure-Tone Thresholds and Cochlear Microphonics Thresholds in Pediatric Cochlear Implant Patients.

In adult cochlear implant patients, conventional audiometry is used to measure postoperative residual hearing which requires active listening and patient feedback. However, audiological measurements in pediatric cochlear implant patients are both challenging as well as time consuming. Intracochlear electrocochleography (ECOG) offers an objective and a time-efficient method to measure frequency-specific cochlear microphonic or difference thresholds (CM/DIF) thresholds that closely approximate auditory thresholds in adult cochlear implant patients. The correlation between CM/DIF and behavioral thresholds has not been established in pediatric cochlear implant patients. In the present study, CM/DIF thresholds were compared with audiometric thresholds in pediatric cochlear implant patients with postoperative residual hearing. Thirteen (11 unilateral and 2 bilateral) pediatric cochlear implant patients (mean age = 9.2 years ± 5.1) participated in this study. Audiometric thresholds were estimated using conventional, condition play, or visual reinforcement audiometry. A warble tone stimulus was used to measure audiometric thresholds at 125, 250, 500, 1000, and 2000 Hz. ECOG waveforms were elicited using 50-msec acoustic tone-bursts. The most apical intracochlear electrode was used as the recording electrode with an extra-cochlear ground electrode. The ECOG waveforms were analyzed to determine CM/DIF thresholds that were compared with pediatric cochlear implant patients' audiometric thresholds. The results show a significant correlation (r = 0.77, p < 0.01) between audiometric and CM/DIF thresholds over a frequency range of 125 to 2000 Hz in pediatric cochlear implant patients. Frequency-specific comparisons revealed a correlation of 0.82, 0.74, 0.69, 0.41, and 0.32 between the audiometric thresholds and CM/DIF thresholds measured at 125, 250, 500, 1000, and 2000 Hz, respectively. An average difference of 0.4 dB (±14 dB) was measured between the audiometric and CM/DIF thresholds. Intracochlear ECOG can be used to measure CM/DIF thresholds in pediatric cochlear implant patients with residual hearing in the implanted ear. The CM/DIF thresholds are similar to the audiometric thresholds at lower test frequencies and offer an objective method to monitor residual hearing in difficult-to-test pediatric cochlear implant patients.

Transient nanostrain detection in phi-OTDR using statistics-based signal processing

Phase-sensitive optical time-domain reflectometry (Φ-OTDR) is capable of detecting acoustic emission induced small strain with high sensitivity. However, there is a tradeoff between sensitivity, bandwidth and detection range, which makes the detection of a transient weak signal challenging. In this work, we focus on transient weak signal detection using Φ-OTDR. To achieve this aim, we propose a cascaded statistics-based signal-processing framework in a Φ-OTDR system to fetch the transient weak signal from a noisy background. Our framework is based on two key elements, including an estimator that is derived based on the probability characteristic of the Rayleigh backscattered light, and a time-frequency feature extraction process that maps the signal to the time-frequency domain. Using our statistics-based signal processing Φ-OTDR, we demonstrate experimentally the detections of, firstly a weak persistent signal with a magnitude down to 4 nε and a frequency up to 40 kHz, and then a weak transient acoustic tone-burst signal. Our proposed scheme is promising for Φ-OTDR performance improvement particularly in weak signal detections, and it will find new applications in the future systems.

Impact of stimulus frequency and recording electrode on electrocochleography in Hybrid cochlear implant users

This report explores the impact of recording electrode position and stimulus frequency on intracochlear electrocochleography (ECoG) responses recorded from six Nucleus L24 Hybrid CI users. Acoustic tone bursts (250 Hz, 500 Hz, 750 Hz, and 1000 Hz) were presented to the implanted ear via an insert earphone. Recordings were obtained from intracochlear electrodes 6 (most basal), 8, 10, 12, 14, 16, 18, 20, and 22 (most apical). Responses to condensation and rarefaction stimuli were subtracted from one another to emphasize hair cell responses (CM/DIF) and added to one another to emphasize neural responses (ANN/SUM). For a fixed stimulus frequency, the CM/DIF and ANN/SUM magnitudes increased as the recording electrode moved apically. For a fixed recording electrode, as the stimulus frequency was lowered, response magnitudes increased. The CM/DIF and ANN/SUM response phase were generally stable across recording electrodes, although substantial phase shifts were noted for a few conditions. Given the recent interest in ECoG for assessing peripheral auditory function in CI users, the impact of stimulus frequency and recording electrode position on response magnitude should be considered. Results suggest optimal ECoG responses are obtained using the most apical recording electrode and a low frequency acoustic stimulus (250 Hz or 500 Hz).

Acoustic Distortion Ratio Enhancement Using Multiple Pulse-Echo Method (MPEM) for Evaluation of B/A Nonlinear Parameter.

In this article, we report on the analysis of the extended acoustic signature obtained from the pulse-echo method to evaluate the B/A nonlinear parameter in fluids. In the known form of the method, the first acoustic tone burst from the reflector is used for the parameter measurement. The multiple pulse-echo method (MPEM) makes use of several tone bursts coming from the reflector back wall. The distortion ratio can be increased when the source frequency is tuned to a reflector resonance. The repercussion of this increase in the measurement of the nonlinear parameter B/A is investigated. As a practical result, this work suggests that the fluid volume required for the measurement can be reduced.

Postoperative Electrocochleography from Hybrid Cochlear Implant users: An Alternative Analysis Procedure

ObjectiveShorter electrode arrays and soft surgical techniques allow for preservation of acoustic hearing in many cochlear implant (CI) users. Recently, we developed a method of using the Neural Response Telemetry (NRT) system built in Custom Sound EP clinical software to record acoustically evoked electrocochleography (ECoG) responses from an intracochlear electrode in Nucleus Hybrid CI users (Abbas et al., 2017). We recorded responses dominated by the hair cells (cochlear microphonic, CM/DIF) and the auditory nerve (auditory nerve neurophonic, ANN/SUM). Unfortunately, the recording procedure was time consuming, limiting potential clinical applications. This report describes a modified method to record the ECoG response more efficiently. We refer to this modified technique as the “short window” method, while our previous technique (Abbas et al., 2017) is referred as the “long window” method. In this report, our goal was to 1) evaluate the feasibility of the short window method to record the CM/DIF and ANN/SUM responses, 2) characterize the reliability and sensitivity of the measures recorded using the short window method, and 3) evaluate the relationship between the CM/DIF and ANN/SUM measures recorded using the modified method and audiometric thresholds. MethodThirty-four postlingually deafened adult Hybrid CI users participated in this study. Acoustic tone bursts were presented at four frequencies (250, 500, 750, and 1000 Hz) at various stimulation levels via an insert earphone in both condensation and rarefaction polarities. Acoustically evoked ECoG responses were recorded from the most apical electrode in the intracochlear array. These two responses were subtracted to emphasize the CM/DIF responses and added to emphasize the ANN/SUM responses. Response thresholds were determined based on visual inspection of time waveforms, and trough-to-peak analysis technique was used to quantify response amplitudes. Within-subject comparison of responses measured using both short and long window methods were obtained from seven subjects. We also assessed the reliability and sensitivity of the short window method by comparing repeated measures from 19 subjects at different times. Correlations between CM/DIF and ANN/SUM measures using the short window recording method and audiometric thresholds were also assessed. ResultsRegardless of the recording method, CM/DIF responses were larger than ANN/SUM responses. Responses obtained using the short window method were positively correlated to those obtained using the conventional long window method. Subjects who had stable acoustic hearing at two different time points had similar ECoG responses at those points, confirming high test-retest reliability of the short window method. Subjects who lost hearing between two different time points showed increases in ECoG thresholds, suggesting that physiologic ECoG responses are sensitive to audiometric changes. Correlations between CM/DIF and ANN/SUM thresholds and audiometric thresholds at all tested frequencies were significant. ConclusionThis study compares two different recording methods. Intracochlear ECoG measures recorded using the short window technique were efficient, reliable, and repeatable. We were able to collect more frequency specific data with the short window method, and observed similar results between the long window and short window methods. Correlations between physiological thresholds and audiometric thresholds were similar to those reported previously using the long window method (Abbas et al., 2017). This is an important finding because it demonstrates that clinically-available software can be used to measure frequency-specific ECoG responses with enhanced efficiency, increasing the odds that this technique might move from the laboratory into clinical practice.

Ageing-related changes in the cortical processing of otolith information in humans.

Acoustic short tone bursts (STB) trigger ocular and cervical vestibular-evoked myogenic potentials (oVEMPs/cVEMPs) by activating irregular otolith afferents. Simultaneously, STBs introduce an artificial net acceleration signal of otolith origin into the vestibular network. VEMP parameters as diagnostic otolith processing markers have been shown to decline after the age of thirty. To delineate the differential effects of healthy ageing on the cortical vestibular subnetwork processing otolith information, we measured cVEMPs and the differential effects of unilateral STB in three age groups (20-40, 40-60 and 60+; n=42) using functional neuroimaging. STB evoked responses in the main vestibular hubs in the parieto-opercular cortex. Whereas cVEMP amplitudes declined linearly with age, analysis of the BOLD response size depicted a u-shaped curve. Vestibular perception of the otolith stimulus on the other hand remained unchanged with age. Therefore, we propose that the comparably larger BOLD responses past the age of sixty could reflect a mechanism of central sensitisation for otolith perception to counterbalance the concurrent peripheral vestibular and somatosensory function decline.

Electrophysiological Evidence of the Basilar-Membrane Travelling Wave and Frequency Place Coding of Sound in Cochlear Implant Recipients

Aim: To obtain direct evidence for the cochlear travelling wave in humans by performing electrocochleography from within the cochlea in subjects implanted with an auditory prosthesis. Background: Sound induces a travelling wave that propagates along the basilar membrane, exhibiting cochleotopic tuning with a frequency-dependent phase delay. To date, evoked potentials and psychophysical experiments have supported the presence of the travelling wave in humans, but direct measurements have not been made. Methods: Electrical potentials in response to rarefaction and condensation acoustic tone bursts were recorded from multiple sites along the human cochlea, directly from a cochlear implant electrode during, and immediately after, its insertion. These recordings were made from individuals with residual hearing. Results: Electrocochleography was recorded from 11 intracochlear electrodes in 7 ears from 6 subjects, with detectable responses on all electrodes in 5 ears. Cochleotopic tuning and frequency-dependent phase delay of the cochlear microphonic were demonstrated. The response latencies were slightly shorter than those anticipated which we attribute to the subjects' hearing loss. Conclusions: Direct evidence for the travelling wave was observed. Electrocochleography from cochlear implant electrodes provides site-specific information on hair cell and neural function of the cochlea with potential diagnostic value.

Sensitivity of the cochlear nerve to acoustic and electrical stimulation months after a vestibular labyrinthectomy in guinea pigs

Single-sided deafness patients are now being considered candidates to receive a cochlear implant. With this, many people who have undergone a unilateral vestibular labyrinthectomy for the treatment of chronic vertigo are now being considered for cochlear implantation. There is still some concern regarding the potential efficacy of cochlear implants in these patients, where factors such as cochlear fibrosis or nerve degeneration following unilateral vestibular labyrinthectomy may preclude their use. Here, we have performed a unilateral vestibular labyrinthectomy in normally hearing guinea pigs, and allowed them to recover for either 6 weeks, or 10 months, before assessing morphological and functional changes related to cochlear implantation. Light sheet fluorescence microscopy was used to assess gross morphology throughout the entire ear. Whole nerve responses to acoustic, vibrational, or electrical stimuli were used as functional measures. Mild cellular infiltration was observed at 6 weeks, and to a lesser extent at 10 months after labyrinthectomy. Following labyrinthectomy, cochlear sensitivity to high-frequency acoustic tone-bursts was reduced by 16 ± 4 dB, vestibular sensitivity was almost entirely abolished, and electrical sensitivity was only mildly reduced. These results support recent clinical findings that patients who have received a vestibular labyrinthectomy may still benefit from a cochlear implant.

Metal electrode direct sound generation in seawater

Thermoacoustic expansion of water due to Ohmic heating and volume changes in the very thin Helmholtz double layer that forms adjacent to metal electrodes are two mechanisms that have been used to explain sound generation by metal electrodes in seawater. Using 20 gauge solid sterling silver wire electrodes with only the circular cross section of the wire exposed, our experiments have demonstrated intense sound production in the form of acoustic tone bursts in seawater from a thermoacoustic mechanism at a second harmonic of 20 kHz of the electrical driving frequency at 10 kHz. Additionally, we observed a separate intense and transient acoustic tone burst generation from a mechanism we attribute to vesicle layer excitation where the vesicle is a highly charged layer of water associated with the boundary of droplets and bubbles. This vesicle layer excitation sound generation mechanism is distinct from any Helmholtz double layer mechanism since the double layer is always present while the acoustic tone burst we observe repeatedly occurs after about 4.4 ms of applied alternating voltage at 10 kHz and last only about 560 μs. We present our experimental setup and results. Moving seawater directly to generate sound may lead to more compact projectors.

Energy conservation and pulse propagation in an elastic medium with quadratic nonlinearity

A sinusoidal acoustic tone-burst launched into an elastic medium with weak quadratic nonlinearity is shown to generate a right-triangular static displacement pulse, when conservation of energy is properly imposed on the model equations. The right-triangular displacement profile is shown to occur whether the tone-burst is modeled with displacement-prescribed or traction-prescribed boundary conditions. Definitive experimental evidence is presented confirming the model predictions. Theoretical arguments and experimental evidence are also presented showing that, contrary to the assertion of Qu et al. [J. Acoust. Soc. Am. 131, 1827 (2012)], the right-triangular shape is not in violation of causality.

Comparison of tone burst versus logon stimulation for vestibular evoked myogenic potentials

The following study has been carried out to compare the effectiveness of logon and tone burst acoustic stimulation to elicit vestibular evoked myogenic potential (VEMP) responses. The methods and the subjects include 31 healthy adult volunteers (62 ears) who were enrolled in this study. Two different acoustic stimuli, logon (L-VEMP) and tone burst (T-VEMP), were used to elicit VEMP responses in each subject. Bilateral recordings with simultaneous binaural acoustic stimulations were used during VEMP recordings. During the recording period, the subjects were in supine position with their head elevated. The results observed were that the response rate of p1n1 wave was 91.9% for L-VEMP and 88.7% for T-VEMP. The response rate of n2p2 wave was 80.6% for L-VEMP, and 75.8% for T-VEMP. There were no significant differences between the two groups with respect to the latencies of p1, n1, n2 and p2, p1n1 and n2p2 interval, and p1n1 and n2p2 amplitude. The conclusion was that there was no difference between logon and tone burst stimulation with respect to VEMP response rates and VEMP parameters. Therefore, they are not superior to each other.

Frequency tuning of bone-conducted tone burst-evoked myogenic potentials recorded from extraocular muscles (BOVEMP) in normal human subjects

In this study, we characterized the frequency tuning of bone-conducted sound-evoked myogenic potentials recorded from extraocular muscles (BOVEMP) in normal human subjects. Experimental design. In a sample of nine subjects, acoustic tone bursts (57 dB nHL, 8 ms plateau, 1 ms rise/fall, alternating polarity) with frequencies from 250 Hz to 2,000 Hz were delivered by a bone oscillator (Radioear B-71) placed on the left mastoid processes. Subjects were required to sit upright and maintain a straight gaze. The BOVEMPs were recorded from surface electrodes placed at four locations around the right eye (superior, inferior, nasal, and temporal) and referenced to an electrode placed at the nape of the neck over cervical vertebrate C7. Signals from electrodes were amplified (10,000 gain) and sampled at 10 kHz and were averaged over 500 repetitions. Short latency biphasic potential were present at each of the four recording sites around the eye. The average latency of the first peak (negative) and the second peak (positive) was 15.7 ± 0.3 ms and 23.3 ± 0.5 ms, respectively. The tuning curve of the BOVEMP was similar at each recording site with largest N1 amplitude following stimulation at 383 Hz (± 17 Hz) and largest P1 amplitude following stimulation at 440 Hz (± 22 Hz). Since the frequency tuning for the bone-conducted sound-evoked OVEMP (BOVEMP) was different from that of the air-conducted sound-evoked OVEMP (AOVEMP), we hypothesize that the BOVEMP and AOVEMP are generated by activation of different vestibular end organs.

Evidence that the compound action potential (CAP) from the auditory nerve is a stationary potential generated across dura mater

We have investigated the generation of the compound action potential (CAP) from the auditory nerve of guinea pigs. Responses to acoustic tone-bursts were recorded from the round window (RW), throughout the cochlear fluids, from the surface of the cochlear nucleus, from the central end of the auditory nerve after removal of the cochlear nucleus, from the scalp vertex, and from the contralateral ear. Responses were compared before, during and after experimental manipulations including pharmacological blockade of the auditory nerve, section of the auditory nerve, section of the efferent nerves, removal of the cochlear nucleus, and focal cooling of the cochlear nerve and/or cochlear nucleus. Regardless of the waveform changes occurring with these manipulations, the responses were similar in waveform but inverted polarity across the internal auditory meatus. The CAP waveforms were very similar before and after removal of the cochlear nucleus, apart from transient changes that could last many minutes. This suggests that the main CAP components are generated entirely by the eighth nerve. Based on previous studies and a clear understanding of the generation of extracellular potentials, we suggest that the early components in the responses recorded from the round window, from the cochlear fluids, from the surface of the cochlear nucleus, or from the scalp are a far-field or stationary potential, generated when the circulating action currents associated with each auditory neurone encounters a high extracellular resistance as it passes through the dura mater.

Experimental study of the acoustic radiation strain in solids

Measurements of the static displacement induced by the radiation stress associated with a longitudinal acoustic wave propagating in a solid are presented. Acoustic tone bursts were launched into fused silica and duraluminum samples. The static displacement was measured at the sample free surface with an optical interferometer. The role of the nonlinearity parameter and the variations of the dc pulse amplitude with the acoustic energy confirm results obtained by other authors. However, our conclusions on the dc pulse shape, on the influence of the tone burst duration, and of the propagation distance on the dc pulse amplitude are different.

Nonperturbing measurements of spatially distributed underwater acoustic fields using a scanning laser Doppler vibrometer.

Localized changes in the density of water induced by the presence of an acoustic field cause perturbations in the localized refractive index. This relationship has given rise to a number of nonperturbing optical metrology techniques for recording measurement parameters from underwater acoustic fields. A method that has been recently developed involves the use of a Laser Doppler Vibrometer (LDV) targeted at a fixed, nonvibrating, plate through an underwater acoustic field. Measurements of the rate of change of optical pathlength along a line section enable the identification of the temporal and frequency characteristics of the acoustic wave front. This approach has been extended through the use of a scanning LDV, which facilitates the measurement of a range of spatially distributed parameters. A mathematical model is presented that relates the distribution of pressure amplitude and phase in a planar wave front with the rate of change of optical pathlength measured by the LDV along a specifically orientated laser line section. Measurements of a 1 MHz acoustic tone burst generated by a focused transducer are described and the results presented. Graphical depictions of the acoustic power and phase distribution recorded by the LDV are shown, together with images representing time history during the acoustic wave propagation.

Time-of-flight estimation based on covariance models

We address the problem of estimating the time-of-flight (ToF) of a waveform thatis disturbed heavily by additional reflections from nearby objects. Theseadditional reflections cause interference patterns that are difficult to predict. Theintroduction of a model for the reflection in terms of a non-stationaryauto-covariance function leads to a new estimator for the ToF of an acoustic toneburst. This estimator is a generalization of the well known matched filter. In manypractical circumstances, for instance beacon-based position estimation in indoorsituations, lack of knowledge of the additional reflections can lead to largeestimation errors. Experiments show that the application of the new estimator canreduce these errors by a factor of about four. The cost of this improvementis an increase in computational complexity by a factor of about seven.

Consequences of hypothyroidism on auditory system function in Tshr mutant (hyt) mice.

The otological consequences of hypothyroidism and the outcome of thyroxin (T4) administration during the developmental period preceding the onset of hearing were examined in mice that express a point mutation in the gene encoding the thyrotropin receptor (Tshr), the so-called hyt mouse. Progeny of sires homozygous for the trait and heterozygous dams were injected with T4 or saline placebo from birth through the tenth postnatal day and auditory-evoked brainstem responses (ABRs) to acoustic clicks and tone bursts were recorded from young adults. Mutant (hyt/hyt) mice exhibited a distinctive pattern of sensory pathology that was characterized by their insensitivity to sound, prolonged response latencies, reduced peak amplitudes, and steep latency-intensity curves relative to the phenotypically normal, euthyroid, +/hyt littermates. Following thyroxin treatment, hyt/hyt mice responded to acoustic stimuli more frequently, were more sensitive to tone bursts throughout their audiometric range, and exhibited decreased latencies and increased amplitudes when compared with placebo-treated homozygous mutants. Although thresholds to acoustic stimuli were improved relative to the untreated group, T4-treated homozygotes were less sensitive than normal, euthyroid individuals. In addition, energy consumption by auditory brainstem nuclei, measured by 2-deoxyglucose (2-DG) uptake, was significantly lower in hyt/hyt mice compared with heterozygotes, and T4 treatment increased the level of 2-DG utilization. Moreover, mean ages for eye-opening and pinna-raising were delayed in animals that were homozygous for the hyt allele. When T4 was administered to hyt/hyt animals, pinna-raising occurred earlier than in untreated animals. A subset of homozygotes exhibited circling behavior, indicative of vestibular and/or motor dysfunction, even though all individuals assumed a normal righting reflex. These findings, including recruitment-like behavior and the restoration of response magnitude at high levels but not low, suggest that the cochlear amplifier is the primary locus of an enduring otological defect associated with hypothyroidism in the Tshr mouse.

Functional development of the inferior colliculus (IC) and its relationship with the auditory brainstem response (ABR) in the tammar wallaby ( Macropus eugenii)

To discover the developmental relationship between the auditory brainstem response (ABR) and the focal inferior colliculus (IC) response, 32 young tammar wallabies were used, by the application of simultaneous ABR and focal brainstem recordings, in response to acoustic clicks and tone bursts of seven frequencies. The IC of the tammar wallaby undergoes a rapid functional development from postnatal day (PND) 114 to 160. The earliest (PND 114) auditory evoked response was recorded from the rostral IC. With development, more caudal parts of the IC became functional until age about PND 127, when all parts of the IC were responsive to sound. Along a dorsoventral direction, the duration of the IC response decreased, the peak latency shortened, while the amplitude increased, reaching a maximum value at the central IC, then decreased. After PND 160, the best frequency (BF) of the ventral IC was the highest, with values between 12.5 and 16 kHz, the BF of the dorsal IC was the lowest, varying between 3.2 and 6.4 kHz, while the BF of the central IC was between 6.4 and 12.5 kHz. Between PND 114 and 125, the IC response did not have temporal correlation with the ABR. Between PND 140 and 160, only the early components of the responses from the ventral and central IC correlated with the P4 waves of the ABR. After PND 160, responses recorded from different depths of the IC had a temporal correlation with the ABR.

Acoustic vaporization of single droplets

It has been observed in the past that droplets in emulsions can be vaporized into gas bubbles by the application of acoustic tone bursts. This paper will show the vaporization of single albumin stabilized droplets as they are exposed to single acoustic tone bursts. An optical microscope was used to monitor single droplets in a flow tube (200 μm diameter). The flow tube was mounted in a small water tank with degassed and heated water (37&amp;lt;th&amp;gt;°C). A single-element focused transducer with a center frequency of 10 MHz was aimed at the intersect of the tube and the optical beam. A highly dilute droplet emulsion was injected into the flow tube and a special syringe setup was used to move the fluid column in the flow tube back and forth to position individual droplets in the volume of interest. A single sinusoidal tone burst (33 cycles at 10 MHz) was sufficient to transition single droplets in the range from 5 to 15 μm diameter. The formation of the corresponding gas bubbles was monitored and measured in the range of 30 to 90 μm. [Work supported by PHS Grant No. R01HL54201 and US Army Grant No. DAMD17-00-1-0344.]