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PubMed2005

Discussant response to 'Does the acoustic waveform mirror the voice?'.

The acoustic waveform that reaches the two ears of a listener can convey the intended message. Over the telephone, this waveform is the only source of information from the speaker, since the listener is out of visual contact; indeed, in this situation the acoustic waveform itself is restricted in its frequency content. Whilst the listener can infer much about the speaker from the acoustic waveform, including the speaker's age, gender, nationality, dialect, and emotional state, the issue under consideration here is the extent to which quantitative analysis of the acoustic waveform can provide useful information about a speaker's voice. This paper was presented as an Invited Discussant Response, at the Pan-European Voice Conference (PEVOC6) in London, to the question posed in Ternström's Invited Keynote Lecture 1: Does the acoustic waveform mirror the voice?

Humans↗
PubMed2000

Acoustic reflectometry profiles of endotracheal and esophageal intubation.

BACKGROUND: Acoustic reflectometry can be used to create a "one-dimensional image" of a cavity, such as the airway and lung, with the image displayed as an area-length curve. This pilot study was undertaken to determine whether acoustic reflectometry could be used to distinguish between an endotracheal and an esophageal intubation. METHODS: Ten adult patients underwent general endotracheal anesthesia and neuromuscular blockade. The reflectometer wavetube was attached to an endotracheal tube, and a reflectometric profile was obtained of the endotracheal tube and the airway and lung cavity. After confirmation of tracheal intubation, a second endotracheal tube was placed in the esophagus. After four breaths were administered, a reflectometric profile of the endotracheal tube-esophagus cavity was obtained. RESULTS: The acoustic reflectometric profiles for tracheal and esophageal intubation profiles were distinctive and characteristic. For an endotracheal tube-airway cavity, the profile shows a constant cross-sectional area throughout the length of the endotracheal tube, followed by a rapid rise in the area past the carina. For an esophageal intubation, the profile shows constant cross-sectional area throughout the length of the endotracheal tube, followed by a sudden decrease in the cross-sectional area to zero. CONCLUSIONS: In this pilot study, acoustic reflectometry within seconds, and without resort to capnography, was able to generate characteristic and distinctive area-length profiles for both endotracheal and esophageal intubation. Acoustic reflectometry may have a role in the emergency imaging of the airway, and in the immediate detection of esophageal intubations, particularly in cases of cardiopulmonary arrest in which the usual techniques for confirmation of breathing tube placement fail.

Acoustics↗
PubMed1986

Acoustic radiation produced by B-71, B-72, and KH 70 bone vibrators.

The amount of acoustic radiation produced by two samples of a Radioear B-71, B-72, and Pracitronic KH 70 bone vibrator was determined for 30 normal-hearing subjects at 4000 Hz. The mean amount of acoustic radiation was very similar for both samples of each vibrator type but significantly (p less than 0.05) different between the bone vibrator types. The mean amount of acoustic radiation averaged over both samples was 8.3 dB for the B-72, 4.3 dB for the B-71, and -0.3 dB for the KH 70. Individual subject data indicated that the B-72 produced excessive acoustic radiation (greater than 5 dB) for 80% of the subjects, the B-71 for 38% of the subjects, and the KH 70 for 8% of the subjects which could cause an invalid high-frequency air-bone gap. Precautions should be taken during bone conduction audiometry to eliminate the possibility of acoustic radiation produced by bone vibrators. A need for additional standards in this area is stressed.

Acoustics↗
PubMed1994

Motivation and methods for manipulating acoustic ringing of earphones.

Transient acoustic stimuli are used for generating auditory evoked responses (AERs). Common transducers do not accurately reproduce transient stimuli, since the transducer diaphragm oscillates at its resonant frequency at the abrupt initiation or termination of a stimulus. These oscillations are called "acoustic ringing." This paper discusses methods for reducing and canceling acoustic ringing, and describes one method, a systems approach, in detail. It also delineates one method for enhancing acoustic ringing. The methods described provide effective techniques for empirical study of the effects of acoustic ringing on AERs or for any application requiring accurate transduction of a transient stimulus.

Acoustics↗
PubMed1996

The utility of acoustic reflex thresholds and other conventional audiologic tests for monitoring cisplatin ototoxicity in the pediatric population.

OBJECTIVE: The sensitivity of acoustic reflex threshold changes for monitoring cisplatin ototoxicity in children was compared with the sensitivity of conventional audiometric tests. DESIGN: Acoustic reflex thresholds, thresholds for audiometric frequencies 0.250 Hz to 2 kHz and 3 kHz to 8 kHz, extended high-frequency (EHF) audiometry for 10 kHz to 16 kHz, and the articulation index (AI) were compared at six different cumulative dosage levels of cisplatin in 21 children, 3.08 yr to 19.25 yr of age. RESULTS: Of these 21 patients, 100% showed significant changes in at least one portion of the test battery when cumulative dosages exceeded 401 mg/m2. EHF testing was found to be the most sensitive to ototoxicity once cumulative dosage levels of 150 to 250 mg/m2 were reached. Audiometric thresholds from 3 to 8 kHz, and acoustic reflex threshold changes were found to be the next most sensitive to ototoxicity at cumulative dosages of 251 to 400 mg/m2. No significant threshold changes were noted for frequencies from 250 Hz to 2 kHz. CONCLUSIONS: Acoustic reflex threshold measures may prove to be a valuable addition to current ototoxic test protocols. Although it is currently not the most sensitive test to ototoxicity, it is one of the more objective tests. Further data must be collected to determine the clinical utility of acoustic reflex threshold testing to monitor ototoxicity.

Adolescent↗
PubMed2002

Acoustic tensor tympani response and vestibular-evoked myogenic potential.

OBJECTIVE: To investigate the acoustic response properties and the vestibular-evoked myogenic potential (VEMP) in various lesions. STUDY DESIGN: Retrospective study of the clinical records of patients. METHODS: Neurotological tests including acoustic response and VEMP were performed and analyzed in 62 patients with facial palsy, otosclerosis, ossicular chain interruption, sensorineural hearing loss, or acoustic tumor. RESULTS: Inverted acoustic responses were observed in 25 of 38 (65.8%) patients with facial palsy, in 5 of 6 (83.3%) patients with acoustic tumor, and in all patients with otosclerosis, ossicular chain interruption, or sensorineural hearing loss. These inverted responses were obtained only when ipsilateral stimulation was used. The thresholds of the inverted responses were statistically significantly higher than those of the normal response. CONCLUSIONS: The vibration of the eardrum is thought to stimulate the ipsilateral trigeminal nerve, leading to contraction of the tensor tympani muscle. The stapedius response had an inhibitory effect on the inverted response. Vibration of the stapes footplate (which requires a normal middle ear conduction system) is necessary to induce the VEMP, whereas the functioning of the facial and cochlear nerves is independent of the VEMP response.

Adult↗
PubMed2005

Conservative management of acoustic neuroma: a meta-analysis and proposed treatment algorithm.

OBJECTIVES/HYPOTHESES: Conservative management is a viable treatment alternative for acoustic neuroma. Using previous studies to provide evidence-based support, we have attempted to more clearly define the role of conservative management. STUDY DESIGN: Retrospective review of literature and patient charts. METHODS: Published studies on conservative management of acoustic neuroma were found using a key word search through PubMed in addition to the bibliographies of these selected studies. A spreadsheet was made to tabulate the selection criteria for conservative management, duration and frequency of follow-up, patient demographics, initial tumor size and rate of growth, change in hearing status, and the need for definitive treatment. RESULTS: A total of 21 studies comprising 1,345 patients were included in our meta-analysis. The average length of follow-up these studies was 3.2 years. The average initial tumor size was 11.8 mm (n = 900); 43% of 1,244 acoustic neuromas showed growth, whereas 57% showed either no growth or tumor regression. The average growth rate was 1.9 mm/year in 793 individuals. Hearing loss occurred in 51% of 347 individuals. In 15 studies, 20.0% of 1,001 individuals eventually failed conservative management. CONCLUSIONS: Our meta-analysis supports the role of conservative management of acoustic neuromas in properly selected patients on the basis of a slow overall rate of growth and a substantial incidence of no growth. However, the lack of predictive factors, the relatively short duration of follow-up, and the variability of inclusion criteria underscore the need for continued collection of long-term data. An algorithm for acoustic neuroma management is proposed based on initial tumor size, patient age, and hearing status.

Algorithms↗
PubMed2006

Effects of programming threshold and maplaw settings on acoustic thresholds and speech discrimination with the MED-EL COMBI 40+ cochlear implant.

OBJECTIVES: The principal task in the programming of a cochlear implant (CI) speech processor is the setting of the electrical dynamic range (output) for each electrode, to ensure that a comfortable loudness percept is obtained for a range of input levels. This typically involves separate psychophysical measurement of electrical threshold ([theta] e) and upper tolerance levels using short current bursts generated by the fitting software. Anecdotal clinical experience and some experimental studies suggest that the measurement of [theta]e is relatively unimportant and that the setting of upper tolerance limits is more critical for processor programming. The present study aims to test this hypothesis and examines in detail how acoustic thresholds and speech recognition are affected by setting of the lower limit of the output ("Programming threshold" or "PT") to understand better the influence of this parameter and how it interacts with certain other programming parameters. DESIGN: Test programs (maps) were generated with PT set to artificially high and low values and tested on users of the MED-EL COMBI 40+ CI system. Acoustic thresholds and speech recognition scores (sentence tests) were measured for each of the test maps. Acoustic thresholds were also measured using maps with a range of output compression functions ("maplaws"). In addition, subjective reports were recorded regarding the presence of "background threshold stimulation" which is occasionally reported by CI users if PT is set to relatively high values when using the CIS strategy. RESULTS: Manipulation of PT was found to have very little effect. Setting PT to minimum produced a mean 5 dB (S.D. = 6.25) increase in acoustic thresholds, relative to thresholds with PT set normally, and had no statistically significant effect on speech recognition scores on a sentence test. On the other hand, maplaw setting was found to have a significant effect on acoustic thresholds (raised as maplaw is made more linear), which provides some theoretical explanation as to why PT has little effect when using the default maplaw of c = 500. Subjective reports of background threshold stimulation showed that most users could perceive a relatively loud auditory percept, in the absence of microphone input, when PT was set to double the behaviorally measured electrical thresholds ([theta]e), but that this produced little intrusion when microphone input was present. CONCLUSIONS: The results of these investigations have direct clinical relevance, showing that setting of PT is indeed relatively unimportant in terms of speech discrimination, but that it is worth ensuring that PT is not set excessively high, as this can produce distracting background stimulation. Indeed, it may even be set to minimum values without deleterious effect.

Acoustic Stimulation↗
PubMed2005

Acoustic schwannomas: awareness of radiologic error will reduce unnecessary treatment.

OBJECTIVE: To measure the intra- and interobserver error in size estimation of acoustic schwannomas from magnetic resonance imaging (MRI) scans by experienced radiologists to determine whether small amounts of tumor growth that may affect management (2 mm) could be reliably measured in clinical practice. DESIGN: Duplicated, blinded size estimation of acoustic neuromas (according to American Academy of Otolaryngology-Head and Neck Surgery guidelines, 1995) from MRI scans of patients with acoustic neuromas. SETTING: Tertiary referral teaching hospital and DGH. PARTICIPANTS: Four radiologists (including 2 dedicated neuroradiologists) measuring positive MRI scans of 26 patients with an acoustic neuroma. MAIN OUTCOME MEASURE: Intraradiologist and inter-radiologist repeatability coefficients in millimeters for the maximal tumor diameter in the anteroposterior (AP) axis, medial-longitudinal (ML) axis, and the square-root of the product of these two measurements. Repeatability coefficients give the 95% range within which the differences in repeated measurements lie. RESULTS: The intraradiologist repeatability for AP and ML measurements ranged from 1.51 to 6.03 mm and 2.01 to 3.83 mm, respectively. The repeatability of the square-root of the product ranged from 1.43 to 4.94 mm. The inter-radiologist repeatability was 6.48 mm and 7.46 mm for the AP and ML measurements, respectively, giving a repeatability of 3.65 mm for the square-root of the product. CONCLUSION: The study indicates that, in routine clinical practice, differences in tumor size of the order of 2 mm cannot be reliably measured, even by the same radiologist. Thus, reported growth of acoustic tumors should be interpreted with caution, especially if this is the criterion for recommending treatment.

Humans↗
PubMed2005

Preservation of hearing in cochlear implant surgery: advantages of combined electrical and acoustical speech processing.

OBJECTIVES/HYPOTHESIS: This study documents the importance of preserving residual low-frequency acoustic hearing as those with more residual hearing are selected for cochlear implantation. Surgical strategies used for hearing preservation with a short hybrid cochlear implant are outlined. The benefits of preserved residual low-frequency hearing, improved word understanding in noise, and music appreciation are described. STUDY DESIGN: Multicenter, prospective, single-subject design. METHODS: Records were reviewed of 21 individuals participating in an Food and Drug Administration (FDA) feasibility clinical trial who have received an Iowa/Nucleus 10 mm electrode. A second group of subjects receiving implants at the University of Iowa that have used the 10 mm device between 2 years and 6 months were also reviewed. Outcome measures included standardized tests of monosyllabic word understanding, spondees in noise, and common melody recognition. RESULTS: Low-frequency hearing was maintained in all individuals immediately postoperative. One subject lost hearing at 2.5 months postoperative after a viral infection. The group has averaged a loss of -9 dB low-frequency acoustic hearing between 125 and 1,000 Hz. Monosyllabic word understanding scores at 6 months for a group being followed for an FDA clinical trial using the implant plus hearing aids was 69% correct. For the long-term group receiving implants at Iowa, monosyllabic word understanding in those who have used the device between 6 months and 2 years is 79%. Other important findings include improved recognition of speech in noise (9 dB improvement) as compared with standard cochlear implant recipients who were matched for speech recognition in quiet and near normal recognition of common melodies. CONCLUSION: The surgical strategies outlined have been successful in preservation of low-frequency hearing in 96% of individuals. Combined electrical and acoustical speech processing has enabled this group of volunteers to gain improved word understanding as compared with their preoperative hearing with bilateral hearing aids and a group of individuals receiving a standard cochlear implant with similar experience with their device. The improvement of speech in noise and melody recognition is attributed to the ability to distinguish fine pitch differences as the result of preserved residual low-frequency acoustic hearing. Preservation of low-frequency acoustic hearing is important for improving speech in noise and music appreciation for the hearing impaired, both of which are important in real-life situations.

Audiometry, Pure-Tone↗
PubMed2003

Effects of acoustic heterogeneity in breast thermoacoustic tomography.

The effects of wavefront distortions induced by acoustic heterogeneities in breast thermoacoustic tomography (TAT) are studied. Amplitude distortions are shown to be insignificant for different scales of acoustic heterogeneities. For wavelength-scale, or smaller, heterogeneities, amplitude distortion of the wavefront is minor as a result of diffraction when the detectors are placed in the far field of the heterogeneities. For larger-scale heterogeneities at the parenchyma wall, by using a ray approach (geometric optics), we show that no refraction-induced multipath interference occurs and, consequently, that no severe amplitude distortion, such as is found in ultrasound tomography, exists. Next, we consider the effects of phase distortions (errors in time-of-flight) in our numerical studies. The numerical results on the spreads of point sources and boundaries caused by the phase distortions are in good agreement with the proposed formula. After that, we demonstrate that the blurring of images can be compensated for by using the distribution of acoustic velocity in the tissues in the reconstructions. The effects of the errors in the acoustical velocities on this compensation also are investigated. An approach to implement the compensation using only TAT data is proposed. Lastly, the differences in the effects of acoustic heterogeneity and the generation of speckles in breast TAT and breast ultrasound imaging are discussed.

Acoustics↗
PubMed2005

A finite-element method model of soft tissue response to impulsive acoustic radiation force.

Several groups are studying acoustic radiation force and its ability to image the mechanical properties of tissue. Acoustic radiation force impulse (ARFI) imaging is one modality using standard diagnostic ultrasound scanners to generate localized, impulsive, acoustic radiation forces in tissue. The dynamic response of tissue is measured via conventional ultrasonic speckle-tracking methods and provides information about the mechanical properties of tissue. A finite-element method (FEM) model has been developed that simulates the dynamic response of tissues, with and without spherical inclusions, to an impulsive acoustic radiation force excitation from a linear array transducer. These FEM models were validated with calibrated phantoms. Shear wave speed, and therefore elasticity, dictates tissue relaxation following ARFI excitation, but Poisson's ratio and density do not significantly alter tissue relaxation rates. Increased acoustic attenuation in tissue increases the relative amount of tissue displacement in the near field compared with the focal depth, but relaxation rates are not altered. Applications of this model include improving image quality, and distilling material and structural information from tissue's dynamic response to ARFI excitation. Future work on these models includes incorporation of viscous material properties and modeling the ultrasonic tracking of displaced scatterers.

Acoustics↗
PubMed1993

Acoustic rhinometry: validation of volume changes following intra-nasal polypectomy.

Acoustic rhinometry measures nasal cavity geometry by analysis of reflected acoustic impulses. Previously, the technique has been applied to normals, patients with septal deviations and rhinitis and to monitor the medical treatment of nasal polyps. To date, no study has been published to validate the application of this technique where nasal polyps are present. In this study, acoustic rhinometry has been used to assess the change in nasal cavity volume following intra-nasal polypectomy in 20 subjects. The volumes of the polyps removed surgically were measured by displacement and compared with the volume change recorded by acoustic rhinometry. A correlation of r = 0.59 (P = < 0.01) has been obtained. Therefore, it is possible to apply acoustic rhinometry as a method of assessing non-surgical treatment of nasal polyps given certain conditions.

Acoustics↗
PubMed2005

Opposite effects of tetanic stimulation of the auditory thalamus or auditory cortex on the acoustic startle reflex in awake rats.

The amygdala mediates both emotional learning and fear potentiation of startle. The lateral amygdala nucleus (LA) receives auditory inputs from both the auditory thalamus (medial geniculate nucleus; MGN) and auditory association cortex (AAC), and is critical for auditory fear conditioning. The central amygdala nucleus, which has intra-amygdaloid connections with LA, enhances startle magnitude via midbrain connections to the startle circuits. Tetanic stimulation of either MGN or AAC in vitro or in vivo can induce long-term potentiation in LA. In the present study, behavioural consequences of tetanization of these auditory afferents were investigated in awake rats. The acoustic startle reflex of rats was enhanced by tetanic stimulation of MGN, but suppressed by that of AAC. All the tetanization-induced changes of startle diminished within 24 h. Blockade of GABAB receptors in the LA area reversed the suppressive effect of tetanic stimulation of AAC on startle but did not change the enhancing effect of tetanic stimulation of MGN. Moreover, transient electrical stimulation of MGN enhanced the acoustic startle reflex when it lagged behind acoustic stimulation, but inhibited the acoustic startle reflex when it preceded acoustic stimulation. The results of the present study indicate that MGN and AAC afferents to LA play different roles in emotional modulation of startle, and AAC afferents are more influenced by inhibitory GABAB transmission in LA.

Acoustic Stimulation↗
PubMed2006

Transcranial fluorescence imaging of auditory cortical plasticity regulated by acoustic environments in mice.

Functional brain imaging using endogenous fluorescence of mitochondrial flavoprotein is useful for investigating mouse cortical activities via the intact skull, which is thin and sufficiently transparent in mice. We applied this method to investigate auditory cortical plasticity regulated by acoustic environments. Normal mice of the C57BL/6 strain, reared in various acoustic environments for at least 4 weeks after birth, were anaesthetized with urethane (1.7 g/kg, i.p.). Auditory cortical images of endogenous green fluorescence in blue light were recorded by a cooled CCD camera via the intact skull. Cortical responses elicited by tonal stimuli (5, 10 and 20 kHz) exhibited mirror-symmetrical tonotopic maps in the primary auditory cortex (AI) and anterior auditory field (AAF). Depression of auditory cortical responses regarding response duration was observed in sound-deprived mice compared with naïve mice reared in a normal acoustic environment. When mice were exposed to an environmental tonal stimulus at 10 kHz for more than 4 weeks after birth, the cortical responses were potentiated in a frequency-specific manner in respect to peak amplitude of the responses in AI, but not for the size of the responsive areas. Changes in AAF were less clear than those in AI. To determine the modified synapses by acoustic environments, neural responses in cortical slices were investigated with endogenous fluorescence imaging. The vertical thickness of responsive areas after supragranular electrical stimulation was significantly reduced in the slices obtained from sound-deprived mice. These results suggest that acoustic environments regulate the development of vertical intracortical circuits in the mouse auditory cortex.

Acoustic Stimulation↗
PubMed2006

Enhanced cochlear acoustic sensitivity and susceptibility to endotoxin are induced by adrenalectomy and reversed by corticosterone supplementation in rat.

Glucocorticoid receptors are widely distributed in the cochlea but their role remains poorly known. Previous studies provided contradictory reports on a possible cochlear acoustic hypersensitivity induced by adrenal insufficiency, while several experiments agree on a significant action of glucocorticoid receptors in adverse conditions such as acoustic trauma and restraint stress. The present experiments confirmed a cochlear acoustic hypersensitivity induced by adrenalectomy and reversed by corticosterone supplementation. These observations point to a significant role of corticosteroids in basal cochlear functioning. The glucocorticoids are known to be essential for limiting and resolving inflammatory processes. The endotoxin Escherichia coli lipopolysaccharide is widely used to induce inflammatory reactions. However, in various organs several toxic processes of this endotoxin are not influenced by glucocorticoids. From previous experiments on the cochlea there is no evidence that glucocorticoids are an essential factor against endotoxin cochlear toxicity. In the present experiments it was found that adrenalectomy greatly increased the cochlear susceptibility to endotoxin; the effect was reversed by providing corticosterone supplementation. This shows the essential role of corticosterone in this cochlear inflammation model. In previous studies local administration (at the cochlear base) of endotoxin was used and losses of cochlear acoustic sensitivity were found predominantly at high frequencies; in contrast, the systemic injection used in this study produced a cochlear loss of acoustic sensitivity at all frequencies, indicating a uniform cochlear sensitivity to the toxic effects of endotoxin.

Acoustic Stimulation↗
PubMed2005

Activation of astrocytes in brain of conscious rats during acoustic stimulation: acetate utilization in working brain.

To evaluate the response of astrocytes in the auditory pathway to increased neuronal signaling elicited by acoustic stimulation, conscious rats were presented with a unilateral broadband click stimulus and functional activation was assessed by quantitative autoradiography using three tracers to pulse label different metabolic pools in brain: [2-14C]acetate labels the 'small' (astrocytic) glutamate pool, [1-14C]hydroxybutyrate labels the 'large' glutamate pool, and [14C]deoxyglucose, reflects overall glucose utilization (CMR(glc)) in all brain cells. CMR(glc) rose during brain activation, and increased activity of the oxidative pathway in working astrocytes during acoustic stimulation was registered with [2-14C]acetate. In contrast, the stimulation-induced increase in metabolic activity was not reflected by greater trapping of products of [1-14C]hydroxybutyrate. The [2-14C]acetate uptake coefficient in the inferior colliculus and lateral lemniscus during acoustic stimulation was 15% and 18% (p < 0.01) higher in the activated compared to contralateral hemisphere, whereas CMR(glc) in these structures rose by 66% (p < 0.01) and 42% (p < 0.05), respectively. Calculated rates of brain utilization of blood-borne acetate (CMR(acetate)) are about 15-25% of total CMR(glc) in non-stimulated tissue and 10-20% of CMR(glc) in acoustically activated structures; they range from 28 to 115% of estimated rates of glucose oxidation in astrocytes. The rise in acetate utilization during acoustic stimulation is modest compared to total CMR(glc), but astrocytic oxidative metabolism of 'minor' substrates present in blood can make a significant contribution to the overall energetics of astrocytes and astrocyte-neuron interactions in working brain.

Acetates↗
PubMed1995

The application of scanning acoustic microscopy in a bone remodeling study.

Scanning acoustic microscopy (SAM) was used in the evaluation of bone remodeling around a cylindrical unicortical defect. SAM is a technique for the nondestructive evaluation of materials, and has only recently been employed as an orthopaedic research tool. The utility of SAM was demonstrated by using it to measure an elastic property known as acoustic impedance. Specifically, the acoustic impedance of bone formed by remodeling around a cylindrical defect was measured. The defects were filled with either a low modulus "void" or rigid inclusion to create various states of stress in the bone in the vicinity of the defect. After six months of implantation of the inclusions in the sheep metatarsal, new bone formation on periosteal and endosteal surfaces about the defect region was observed. These regions of new bone were less stiff and had 18.0 +/- 6.5% lower acoustic impedance than the pre-existing bone in the intracortical region of the metatarsal. There was no difference in the degree of new bone formation about void and rigid inclusions. Both underwent significant adaptational changes in response to the elevated stress about the defect. These changes affected the basic structure of the bone cross-section at the level of the defect and effectively reduced the stress levels about the defect. By using SAM to measure acoustic impedance, it was seen that little internal remodeling occurred in the intracortical region. Hence, the primary mechanism of strain-induced bone remodeling observed in this experimental model was surface remodeling.

Acoustics↗