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Erik Borg - One of the best experts on this subject based on the ideXlab platform.

  • mri acoustic noise Sound Pressure and frequency analysis
    Journal of Magnetic Resonance Imaging, 1997
    Co-Authors: Allen S Counter, Ake Olofsson, Hans Grahn, Erik Borg
    Abstract:

    The large gradient colls used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The Sound Pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo Tl/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multi-peaked spectra. Slice thickness and SPL were inversely related, and Tl-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unflltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately.

  • mri acoustic noise Sound Pressure and frequency analysis
    Journal of Magnetic Resonance Imaging, 1997
    Co-Authors: Allen S Counter, Ake Olofsson, Hans Grahn, Erik Borg
    Abstract:

    The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The Sound Pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.

Allen S Counter - One of the best experts on this subject based on the ideXlab platform.

  • mri acoustic noise Sound Pressure and frequency analysis
    Journal of Magnetic Resonance Imaging, 1997
    Co-Authors: Allen S Counter, Ake Olofsson, Hans Grahn, Erik Borg
    Abstract:

    The large gradient colls used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The Sound Pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo Tl/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multi-peaked spectra. Slice thickness and SPL were inversely related, and Tl-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unflltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately.

  • mri acoustic noise Sound Pressure and frequency analysis
    Journal of Magnetic Resonance Imaging, 1997
    Co-Authors: Allen S Counter, Ake Olofsson, Hans Grahn, Erik Borg
    Abstract:

    The large gradient coils used in MRI generate, simultaneously with the pulsed radiofrequency (RF) wave, acoustic noise of high intensity that has raised concern regarding hearing safety. The Sound Pressure levels (SPLs) and power spectra of MRI acoustic noise were measured at the position of the human head in the isocenter of five MRI systems and with 10 different pulse sequences used in clinical MR scanning. Each protocol, including magnetization-prepared rapid gradient echo (MP-RAGE; 113 dB SPL linear), fast gradient echo turbo (114 dB SPL linear), and spin echo T1/2 mm (117 dB SPL linear), was found to have the high SPLs, rapid pulse rates, amplitude-modulated pulse envelopes, and multipeaked spectra. Since thickness and SPL were inversely related, the T1-weighted images generated more intense acoustic noise than the proton-dense T2-weighted measures. The unfiltered linear peak values provided more accurate measurements of the SPL and spectral content of the MRI acoustic noise than the commonly used dB A-weighted scale, which filters out the predominant low frequency components. Fourier analysis revealed predominantly low frequency energy peaks ranging from .05 to approximately 1 kHz, with a steep high frequency cutoff for each pulse sequence. Ear protectors of known attenuation ratings are recommended for all patients during MRI testing.

Bo Hakansson - One of the best experts on this subject based on the ideXlab platform.

  • estimation of bone conduction skull transmission by hearing thresholds and ear canal Sound Pressure
    Hearing Research, 2013
    Co-Authors: Sabine Reinfeldt, Stefan Stenfelt, Bo Hakansson
    Abstract:

    Bone conduction Sound transmission in the human skull and the occlusion effect were estimated from hearing thresholds and ear-canal Sound Pressure (ECSP) measured by a probe tube microphone when st ...

  • examination of bone conducted transmission from Sound field excitation measured by thresholds ear canal Sound Pressure and skull vibrations
    Journal of the Acoustical Society of America, 2007
    Co-Authors: Sabine Reinfeldt, Stefan Stenfelt, Tobias Good, Bo Hakansson
    Abstract:

    Bone conduction (BC) relative to air conduction (AC) Sound field sensitivity is here defined as the perceived difference between a Sound field transmitted to the ear by BC and by AC. Previous investigations of BC-AC Sound field sensitivity have used different estimation methods and report estimates that vary by up to 20 dB at some frequencies. In this study, the BC-AC Sound field sensitivity was investigated by hearing threshold shifts, ear canal Sound Pressure measurements, and skull bone vibrations measured with an accelerometer. The vibration measurement produced valid estimates at 400 Hz and below, the threshold shifts produced valid estimates at 500 Hz and above, while the ear canal Sound Pressure measurements were found erroneous for estimating the BC-AC Sound field sensitivity. The BC-AC Sound field sensitivity is proposed, by combining the present result with others, as frequency independent at 50 to 60 dB at frequencies up to 900 Hz. At higher frequencies, it is frequency dependent with minima of 40 to 50 dB; at 2 and 8 kHz, and a maximum of 50 to 60 dB at 4 kHz. The BC-AC Sound field sensitivity is the theoretical limit of maximum attenuation achievable with ordinary hearing protection devices. (c) 2007 Acoustical Society of America.

John J. Rosowski - One of the best experts on this subject based on the ideXlab platform.

  • Differential Intracochlear Sound Pressure Measurements in Normal Human Temporal Bones
    Journal of the Association for Research in Otolaryngology, 2008
    Co-Authors: Hideko Heidi Nakajima, Elizabeth S. Olson, Saumil N. Merchant, Michael E. Ravicz, Wei Dong, John J. Rosowski
    Abstract:

    We present the first simultaneous Sound Pressure measurements in scala vestibuli and scala tympani of the cochlea in human cadaveric temporal bones. The technique we employ, which exploits microscale fiberoptic Pressure sensors, enables the study of differential Sound Pressure at the cochlear base. This differential Pressure is the input to the cochlear partition, driving cochlear waves and auditory transduction. In our results, the Sound Pressure in scala vestibuli ( P _SV) was much greater than scala tympani Pressure ( P _ST), except for very low and high frequencies where P _ST significantly affected the input to the cochlea. The differential Pressure ( P _SV − P _ST) is a superior measure of ossicular transduction of Sound compared to P _SV alone: ( P _SV− P _ST) was reduced by 30 to 50 dB when the ossicular chain was disarticulated, whereas P _SV was not reduced as much. The middle ear gain P _SV/ P _EC and the differential Pressure normalized to ear canal Pressure ( P _SV − P _ST)/ P _EC were generally bandpass in frequency dependence. At frequencies above 1 kHz, the group delay in the middle ear gain is about 83 μs, over twice that of the gerbil. Concurrent measurements of stapes velocity produced estimates of cochlear input impedance, the differential impedance across the partition, and round window impedance. The differential impedance was generally resistive, while the round window impedance was consistent with compliance in conjunction with distributed inertia and damping. Our technique of measuring differential Pressure can be used to study inner ear conductive pathologies (e.g., semicircular dehiscence), as well as non-ossicular cochlear stimulation (e.g., round window stimulation and bone conduction)—situations that cannot be completely quantified by measurements of stapes velocity or scala vestibuli Pressure by themselves.

  • Sound Pressure distribution and power flow within the gerbil ear canal from 100 hz to 80 khz
    Journal of the Acoustical Society of America, 2007
    Co-Authors: Michael E. Ravicz, Elizabeth S. Olson, John J. Rosowski
    Abstract:

    Sound Pressure was mapped in the bony ear canal of gerbils during closed-field Sound stimulation at frequencies from 0.1to80kHz. A 1.27-mm-diam probe-tube microphone or a 0.17-mm-diam fiber-optic miniature microphone was positioned along approximately longitudinal trajectories within the 2.3-mm-diam ear canal. Substantial spatial variations in Sound Pressure, sharp minima in magnitude, and half-cycle phase changes occurred at frequencies >30kHz. The Sound frequencies of these transitions increased with decreasing distance from the tympanic membrane (TM). Sound Pressure measured orthogonally across the surface of the TM showed only small variations at frequencies below 60kHz. Hence, the ear canal Sound field can be described fairly well as a one-dimensional standing wave pattern. Ear-canal power reflectance estimated from longitudinal spatial variations was roughly constant at 0.2–0.5 at frequencies between 30 and 45kHz. In contrast, reflectance increased at higher frequencies to at least 0.8 above 60kHz. ...

Thomas J Imig - One of the best experts on this subject based on the ideXlab platform.