PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 2210101

Bone vibrator placement and the cancellation technique.

J J Dempsey·H Levitt
View original source ↗Export metadata ↓

Abstract

An issue in the measurement of bone conduction sensitivity is the placement of the bone vibrator. The effect of bone vibrator position on the amplitude and phase of the received signal was investigated using a cancellation technique. This technique involves cancelling the signal delivered by the bone vibrator with a signal delivered acoustically via an earphone. At cancellation, the acoustic signal is equal in amplitude but opposite in phase to the bone-conducted signal. Results showed that the amplitude of the received signal did not vary significantly with bone vibrator position close to the center of the forehead whereas the phase of the received signal was critically dependent on bone vibrator position. Substantial intersubject differences were observed in the variation of phase with bone vibrator position. The precision of measurement using the cancellation technique was found to be high.

Explore related subjects

AcousticsBone ConductionCochleaForeheadHumansMastoidVibrationJournal ArticleResearch Support, U.S. Gov't, Non-P.H.S.

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

J J Dempsey, H Levitt. 1990. Bone vibrator placement and the cancellation technique.. https://doi.org/10.1097/00003446-199008000-00004

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2007

Effects of gamma irradiation on mechanical properties of defatted trabecular bone allografts assessed by speed-of-sound measurement.

New sterilization methods for human bone allografts may lead to alterations in bone mechanical properties, which strongly influence short- and medium-term outcomes. In many sterilization procedures, bone allografts are subjected to gamma irradiation, usually with 25 KGy, after treatment and packaging. We used speed-of-sound (SOS) measurements to evaluate the effects of gamma irradiation on bone. All bone specimens were subjected to the same microbial inactivation procedure. They were then separated into three groups, of which one was treated and not irradiated and two were exposed to 10 and 25 KGy of gamma radiation, respectively. SOS was measured using high- and low-frequency ultrasound beams in each orthogonal direction. SOS and Young modulus were altered significantly in the three groups, compared to native untreated bone. Exposure to 10 or 25 KGy had no noticeable effect on the study variables. The impact of irradiation was small compared to the effects of physical or chemical defatting. Reducing the radiation dose used in everyday practice failed to improve graft mechanical properties in this study.

Acoustics↗
PubMed2007

Objective and subjective evaluation of the acoustic comfort in classrooms.

The acoustic comfort of classrooms in a Brazilian public school has been evaluated through interviews with 62 teachers and 464 pupils, measurements of background noise, reverberation time, and sound insulation. Acoustic measurements have revealed the poor acoustic quality of the classrooms. Results have shown that teachers and pupils consider the noise generated and the voice of the teacher in neighboring classrooms as the main sources of annoyance inside the classroom. Acoustic simulations resulted in the suggestion of placement of perforated plywood on the ceiling, for reduction in reverberation time and increase in the acoustic comfort of the classrooms.

Acoustics↗
PubMed2007

Analysis of effective radiating area, power, intensity, and field characteristics of ultrasound transducers.

OBJECTIVE: To characterize the ultrasound fields produced by a cohort of transducers from a single manufacturer via hydrophone and Schlieren technology. DESIGN: Descriptive study. SETTING: Measurement laboratory. PARTICIPANTS: Seven same-model ultrasound transducers from a single manufacturer. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Effective radiating area (ERA), total power, spatial average intensity (SAI), beam nonuniformity ratio (BNR), and Schlieren beam widths at 1.0 and 3.3 MHz. RESULTS: Values for ERA (1.0 MHz range, 3.62-4.38 cm(2); 3.3 MHz range, 3.74-4.76 cm(2)), total power (1.0 MHz range, 5.0-5.6 W; 3.3 MHz range, 4.7-5.7 W), SAI (1.0 MHz range, 1.2-1.4 W/cm(2); 3.3 MHz range, 1.0-1.5 W/cm(2)), and BNR (1.0 MHz range, 2.79-5.85; 3.3 MHz range, 2.51-4.56) fell within manufacturer's specifications and U.S. Food and Drug Administration (FDA) regulations. Schlieren analysis showed significantly larger beam widths at 3.3 MHz compared with 1.0 MHz and a large degree of variability in the ultrasound fields generated by the different transducers. There were no significant correlations between beam widths and ERA values. CONCLUSIONS: ERA and total power values in a test cohort exist within a range that met FDA regulations. Individual variability in ERA and total power resulted in 50% variability in SAI. This variability may help explain previous reports of heating differences between transducers.

Acoustics↗