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At least 235 records · Page 13Linked to original sources
PubMed2002

Response of human skull to bone-conducted sound in the audiometric-ultrasonic range.

Some new therapies for tinnitus employ bone-conducted sound in the high audio and ultrasonic frequencies, but there has been little previous research on sound transmission through the head at these frequencies. The vibrational characteristics of two dry skulls, in comparison to a live human head, were measured in the 2- to 52-kHz range. White noise was played and received through piezoelectric transducers and was Fourier-analyzed. Complex resonances and antiresonances were found in both the dry skulls and the live head and varied with small changes in the position of the transducers. There were also pronounced differences between the skulls. In comparison to the skulls, the live head showed greater attenuation and less prominent resonances and antiresonances, reflecting greater damping. The attenuation of the skulls and the head did not increase consistently with frequency but was dominated by resonances at a variety of frequencies. For designing high audio and ultrasonic tinnitus maskers and hearing aids, these results suggest that wide bandwidth must be used to compensate for the unpredictability of the resonances.

Adult↗
PubMed1979

Air-borne radiation from bone conduction transducers.

The relative magnitudes of air-borne radiation and mechanical vibration from three types of bone conduction transducer have been measured. The study suggests that the presence of excess air-borne radiation can lead to the observation of a false air-bone gap in audiometry. Some methods of overcoming this effect are considered.

Air↗
PubMed1981

Loudness balance calibration of bone conduction vibrators.

An improved monaural loudness balance method of transferring calibration data among three physically dissimilar bone conduction vibrators was compared with the threshold method. In 19 of 21 possible comparisons, absolute differences between the transfer factors obtained with the two methods were 2.5 dB or less, showing that the monaural loudness balance procedure compares favorably with the threshold method.

Adult↗
PubMed1983

Bone-conducted auditory stimulation in unrestrained, unanesthetized animals.

A new method of eliciting auditory responses using bone-conducted stimuli was developed for use in freely-moving unanesthetized animals. In cats and rats piezoelectric materials were either bolted to or embedded within a dental acrylic skull platform. In order to produce acoustic stimulation, click and pip electrical waveforms were used to drive vibrations in the crystalline material. Responses to the crystal-elicited stimuli were compared with responses to air-coupled stimuli and were found to be virtually identical. Acoustic masking eliminated the response showing there is no significant contribution made to the responses by other sensory modalities.

Acoustic Stimulation↗
PubMed1989

Auditory brain stem responses to bone-conducted tones in infants.

The auditory brain stem responses (ABRs) to 500- and 2,000-Hz bone-conducted (BC) tones were recorded from 48 infants with ears exhibiting various external and middle ear states (normal, otitis media, auditory meatal atresia). Amplitudes were greater, wave V latencies longer, and detectability better for responses to 500-Hz BC tones compared to 2,000-Hz BC tones. Overall, most (94% to 100%) infants with normal cochlear sensitivity demonstrate ABRs to 20-dB normal hearing level (nHL) 500-Hz BC tones and 30-dB nHL 2,000-Hz BC tones. In cases in which masking is difficult (eg, bilateral atresia), infant ipsilateral/contralateral ABR asymmetries may help determine from which cochlea a response to the BC tones originates. In conclusion, two-channel ABR recordings to BC tones appear to be feasible for demonstrating normal cochlear sensitivity in infants.

Audiometry, Evoked Response↗
PubMedDate not supplied

Electrocochleography with bone-conducted stimulation. A comparative study of different methods of stimulation.

Due to the shortcomings of the conventional bone vibrators available at the present, electrocochleography with bone conducted acoustic stimulation has not found any clinical application despite the fact that methods for the procedure have been developed for some time. The most striking deficiencies of these vibrators are their unsatisfactory stimulus intensities and their lack of frequency specificity due to distortion. Driven by an a.c. signal, a piezoceramic accelerometer (A21T, D. J. Birchall Ltd.) was found to meet the requirements of clinical use giving satisfactory stimulus intensities with a minimum of distortion when attached to the mastoid process by means of a modified bone screw.

Acoustic Stimulation↗
PubMedDate not supplied

Frequency-specific brainstem responses to bone-conducted tone pulses masked by notched noise.

As in the case of auditory brainstem responses (ABRs) to air-conducted stimuli, recording of frequency-specific ABRs to bone-conducted stimuli needs adequate masking of those parts of the basilar membrane that are not to contribute to the ABR. The present study shows that tone-pulse stimulation with notched noise-masking can be realized via a bone vibrator after its frequency response has been flattened. The latency-intensity curves for 4, 2, 1, and 0.5 kHz run approximately parallel, indicating the ABR to be indeed frequency-specific. As adequate air-conducted masking of the nontest ear can produce cross-masking, the use of an insert earphone is proposed. Because of its higher interaural attenuation, a higher masking level can be applied to the nontest ear.

Bone Conduction↗
PubMed1996

Drilling in ear surgery. A comparison of pre- and postoperative bone-conduction thresholds in both the conventional and extended high-frequency ranges.

The pre- and postoperative bone-conduction thresholds for the frequencies 0.25 through 16 kHz were compared in 46 ears in which a high-speed ear drill was used. In 15 of these, thresholds were also obtained in the contralateral ear. There was no statistically significant postoperative threshold change at any single frequency in either the operated or the contralateral ear. The mean threshold elevation of 1.4 dB for the ipsilateral extended high-frequency octave of 8-16 kHz was marginally significant (p = 0.02), while this was not the case in the contralateral, unoperated ear. These findings are considered to be due to difficulties in placement of the cumbersome Präcitronic KH70 vibrator following bone removal ipsilaterally, with resultant defective transmission to the skull.

Adolescent↗
PubMed2003

Factors contributing to bone conduction: the outer ear.

The ear canal sound pressure and the malleus umbo velocity with bone conduction (BC) stimulation were measured in nine ears from five cadaver heads in the frequency range 0.1 to 10 kHz. The measurements were conducted with both open and occluded ear canals, before and after resection of the lower jaw, in a canal with the cartilage and soft tissues removed, and with the tympanic membrane (TM) removed. The sound pressure was about 10 dB greater in an intact ear canal than when the cartilage part of the canal had been removed. The occlusion effect was close to 20 dB for the low frequencies in an intact ear canal; this effect diminished with sectioning of the canal. At higher frequencies, the resonance properties of the ear canal determined the effect of occluding the ear canal. Sectioning of the lower jaw did not significantly alter the sound pressure in the ear canal. The sound radiated from the TM into the ear canal was investigated in four temporal bone specimens; this sound is significantly lower than the sound pressure in an intact ear canal with BC stimulation. The malleus umbo velocity with air conduction stimulation was investigated in nine temporal bone specimens and compared with the umbo velocity obtained with BC stimulation in the cadaver heads. The results show that for a normal open ear canal, the sound pressure in the ear canal with BC stimulation is not significant for BC hearing. At threshold levels and for frequencies below 2 kHz, the sound in the ear canal caused by BC stimulation is about 10 dB lower than air conduction hearing thresholds; this difference increases at higher frequencies. However, with the ear canal occluded, BC hearing is dominated by the sound pressure in the outer ear canal for frequencies between 0.4 and 1.2 kHz.

Auditory Threshold↗
PubMed2006

Bone conduction in a three-dimensional model of the cochlea.

Hearing sensations are caused by air- and bone-guided sound. Of course, other biological materials like tendons, muscles and tissue are also involved during conduction of sound. To study the influence of bone conduction, a formerly developed finite element model was excited by harmonic pressure signals at the cochlea wall. The clinical finding during middle ear surgery, namely the increase in bone conduction sensitivity with removed footplate, was confirmed. Other psychoacoustic effects with bone conduction are described in the early experiments by Bárány, who proved the cancellation of air- and bone-conducted sound in humans. The simultaneous stimulation of the cochlea wall and the phase-reversed stimulation of the stapes footplate in the finite element model confirmed his findings. Further clues to the solution of unsolved problems in audiology and middle ear pathology are given.

Acoustic Stimulation↗
PubMed2000

Vibration characteristics of bone conducted sound in vitro.

A dry skull added with damping material was used to investigate the vibratory pattern of bone conducted sound. Three orthogonal vibration responses of the cochleae were measured, by means of miniature accelerometers, in the frequency range 0.1-10 kHz. The exciter was attached to the temporal, parietal, and frontal bones, one at the time. In the transmission response to the ipsilateral cochlea, a profound low frequency antiresonance (attenuation) was found, verified psycho-acoustically, and shown to yield a distinct lateralization effect. It was also shown that, for the ipsilateral side, the direction of excitation coincides with that of maximum response. At the contralateral cochlea, no such dominating response direction was found for frequencies above the first skull resonance. An overall higher response level was achieved, for the total energy transmission in general and specifically for the direction of excitation, at the ipsilateral cochlea when the transducer was attached to the excitation point closest to the cochlea. The transranial attenuation was found to be frequency dependent, with values from -5 to 10 dB for the energy transmission and -30 to 40 dB for measurements in a single direction, with a tendency toward higher attenuation at the higher frequencies.

Acoustic Stimulation↗
PubMed2005

Nonlinear explanation for bone-conducted ultrasonic hearing.

Human listeners can perceive speech from a voice-modulated ultrasonic carrier presented via a bone-conduction stimulator. This study explored the psychoacoustic characteristics and underlying mechanisms of ultrasonic hearing by measuring difference limens for frequency (DLF) for pure tones modulated onto ultrasonic carriers. Human subjects were presented with two pulsed tones and asked to judge whether the first or the second had the higher pitch. When amplitude modulation was based on a double side-band transmitted carrier, the DLFs were as small as those from the air-conducted pure tones at 0.25-4 kHz. Ultrasounds yielded larger DLFs for tones with low (0.125 kHz) and high (6-8 kHz) frequencies. Results were essentially identical between the two types of carriers, sine wave (30 kHz) and bandpass noise (30+/-4 kHz), despite the different bandwidths in the ultrasonic range. When amplitude modulation was based on a double side-band suppressed carrier, DLFs corresponded to those from tones with double frequencies. These results suggest nonlinear conduction that demodulates audible signals from ultrasounds and provides inputs to the cochlea.

Acoustic Stimulation↗
PubMed2005

Normative data for P1/N1-latencies of vestibular evoked myogenic potentials induced by air- or bone-conducted tone bursts.

OBJECTIVE: The response characteristics of acoustically elicited vestibular evoked myogenic potentials (VEMPs) largely depend on the stimuli applied. A tone-burst stimulation of 500 Hz seems to be clinically most appropriate because those VEMPs can be elicited at the lowest stimulus intensity possible. The aim of the present paper was to describe normative data for tone-burst evoked VEMPs. METHODS: VEMPs of 64 healthy subjects were recorded ipsilaterally during air- or bone-conducted tone burst stimulation. The EMG of the tonically activated sternocleidomastoid muscle was recorded ipsilaterally by surface electrodes. Averages were taken for P1/N1-latencies and -amplitudes of male and female volunteers within 3 different age groups. RESULTS: The latencies did not show any significant differences between female and male volunteers or between air- and bone-conducted stimulation. The latencies did also not show any significant difference among the 3 age groups. The limits for normal latencies (mean + 2 SD) are, therefore, 20.3 ms for P1 and 28.0 ms for N1. Although the P1/N1-amplitudes were decreased with increasing age, the tonic muscle activity was not significantly different between the age groups. CONCLUSIONS: The present findings strongly suggest the evaluation of VEMP latencies by using normative values obtained exactly with the same stimulus parameters. SIGNIFICANCE: Normative data as described in the present study are required to detect isolated saccular defects which are indicative of a vestibular disorder.

Acoustic Stimulation↗
PubMed1978

Bone-conduction electrocochleography: clinical applications.

Cases are presented which show the clinical utility of recording an electrocochleographic response to bone-conducted stimuli. The procedure is fraught with problems of acoustic control and artifact generation, but has distinct although limited values in clarifying masking dilemmas in patients with bilateral hearing loss.

Adolescent↗
PubMedDate not supplied

Unoccluded bone conduction screening as an alternative to impedance screening.

The present study was undertaken to determine which intensity level of an unoccluded bone-conducted (BC) signal might be best suited for use as a supplemental procedure to an individual pure-tone air-conduction school screening program. Four intensity levels (0, 5, 10, 15 dB hearing level) of a 500 Hz BC tone were presented in ascending order to a public school population in addition to screening by impedance audiometry and pure-tone air conducted signals. Tetrachoric analysis using impedance screening results as a standard comparison revealed that a 10-dB unoccluded BC signal at 500 Hz provided an effective supplemental procedure for identifying conductive pathology in the population studied.

Audiometry↗
PubMed1986

Collapse of the ear canal during masking for bone conduction.

Although it is well recognized that collapse of the external meatus can mimic a conductive hearing loss in the test ear, attention must also be directed to the masked ear during masked bone conduction threshold testing. Failure to recognize collapse of the masked ear may result in a false air-bone gap in the test ear. Two such cases are presented and the mechanism analyzed. Suggestions as to identification and resolution of this problem are discussed.

Acoustic Impedance Tests↗