Diego Turo | The Catholic University of America (original) (raw)
Papers by Diego Turo
Journal of the Acoustical Society of America, Sep 30, 2023
Journal of the Acoustical Society of America, Sep 30, 2023
Physical review, Aug 12, 2022
Dirac points in the band structure of acoustic systems are essential features affording classical... more Dirac points in the band structure of acoustic systems are essential features affording classical analogs of quantum condensed matter states. We show that measured dispersion curves near and at the Dirac point of an acoustic graphene analog can be suppressed by strong variations in the impedance boundary between free field and surface wave regimes under certain conditions. Increased Rayleigh scattering and diffractive excitation are shown to increase the dispersed surface wave pressure amplitude, circumventing the impedance-based wave suppression. The improved excitation and scattering conditions for observing acoustic Dirac points for two samples with two distinct operational frequency ranges are reported.
Proceedings of Meetings on Acoustics, 2020
This work presents a comparison between existing simple atmospheric temperature models and experi... more This work presents a comparison between existing simple atmospheric temperature models and experimental measurements of the lower atmospheric boundary layer. This work is part of a larger project developing an improved numerical model of atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. In this study, temperature, humidity, and pressure data are collected with the use of sensors mounted on an unmanned aerial vehicle. Vertical measured temperature profiles are compared to existing common models and assumptions to gain a better understanding of how sufficient these models are at representing the meteorological parameters that will affect acoustic transmission. Representative transmission loss case studies comparing measured and model temperature profiles are included. Temperature profiles that do not represent the observed very near surface warming present in the case study lead to predicted transmission loss values differing by up to 15 dB over a 300 m range.
Journal of the Acoustical Society of America, Sep 1, 2018
The development of various propagation ducting phenomena (elevated or surface) has been studied e... more The development of various propagation ducting phenomena (elevated or surface) has been studied extensively for electromagnetic and electro-optical wave propagation. The influence of changes in temperature, pressure, and humidity gradients on the strength and geometry of the duct in the electromagnetic propagation problem is well-documented, and there is substantial literature regarding the influence of temperature gradient on atmospheric acoustic propagation. Analytical results indicate that moisture gradients in warm air above a sea surface contribute meaningfully to the refraction of sound. This work uses numerical simulation to explore the atmospheric conditions that would support development of acoustic ducts or wave guide conditions during moderate range (<1 km) acoustic propagation. The aim of this overall effort is an improved numerical model of acoustic refraction and attenuation over moderate to long distances above a sea surface that accounts for sea state as well as boundary layer wind, temperature, and humidity profiles.
Journal of the Acoustical Society of America, Oct 1, 2019
This work will investigate two non-destructive methods of fault detection in laminate structures ... more This work will investigate two non-destructive methods of fault detection in laminate structures such as frescos. These two techniques are compared on a purpose-built laboratory prototype and on frescos in the Senate Reception Room of the U.S. Capitol Building. Thermography uses an infrared camera to map the surface temperature of an object. This technique can be used to quickly identify abnormally hot or cold regions on a surface. These abnormal regions can indicate structural defects such as fresco delamination, cracks, and inclusions. The other non-destructive technique for defect detection used in this work is laser Doppler vibrometry paired with acoustic excitation of the target surface. Over the same surface area, thermography provides a much quicker result. This work aims to evaluate potential synergy between the technologies by comparing the results of the two scans. A prototype with known defects is used to find commonality between the two methods and to understand the circumstances in which the results diverge. The prototype is a square of approximately half a meter on each side. A seven centimeter thick concrete backing layer is followed by a layer of mortared antique bricks and topped by mortar and plaster to mimic fresco.
Journal of the Acoustical Society of America, Oct 1, 2014
The two-microphone transfer function method has become the most widely used method of impedance t... more The two-microphone transfer function method has become the most widely used method of impedance tube testing. Due to its measurement speed and ease of implementation, it has surpassed the standing-wave ratio method in popularity despite inherent frequency limitations due to tube geometry. Currently, the two-microphone technique is described in test standards ASTM E1050 and ISO 10534-2 to ensure accurate measurement. However, while detailed for correct test execution, the standards contain vague recommendations for a variety of measurement parameters. For instance, it is only stated in ASTM E1050 that “tube construction shall be massive so sound transmission through the tube wall is negligible.” To quantify this requirement, damping of the tube was varied to determine how different loss factor values effect measured absorption coefficient values. Additional sources of error explored are the amount of required absorbing material within the tube for reflective material measurements, additional calibration methods needed for test of excessive reflective materials, and alternate methods of combating microphone phase error and tube attenuation.
Applied Acoustics, Oct 1, 2022
Journal of the Acoustical Society of America, Mar 1, 2023
Journal of the Acoustical Society of America, Mar 1, 2023
There are many factors that must be considered in the study of atmospheric sound propagation over... more There are many factors that must be considered in the study of atmospheric sound propagation over long distances; these include surface characteristics as well as wind speed and air temperature profiles. This work presents measurements of air temperature profiles over various surfaces. Building a catalogue of this type can enable more realistic case assumptions to be made in an atmospheric acoustic transmission loss model. Accurate air temperature profiles are critical because of the potentially significant impact on the transmission loss predictions. Air temperature profile measurements have been collected by solar radiation shielded temperature loggers mounted 1 m apart on a 7 m mast. Long duration measurements were taken to capture the variability in day and nighttime temperature differentials present over surfaces such as: gravel, vegetated shoreline, marsh grass, lawn grass, water, and asphalt. In particular, measurements performed off shore were done by placing the sensor array on the deck of a pontoon boat. The initial results revealed that this configuration captures a very low elevation warming due to re-radiation from the deck of a boat instead of the true over water temperature. This study highlights the influence of wind speed on the development of the near surface temperature inversions.
Journal of the Acoustical Society of America, Mar 1, 2023
The dispersion of bound acoustic surface waves over hexagonal lattices of resonant cavities has b... more The dispersion of bound acoustic surface waves over hexagonal lattices of resonant cavities has been shown to be analogous to the dispersion of charge transport in carbon graphene. Of particular interest is the frequency range close to the acoustic Dirac point where novel physics is predicted to occur. In this study, we measure the dispersion curves of a single-layer acoustic graphene analogue with high resolution one-dimensional spatial scansand show how the curves can be suppressed (near and at the Dirac point) by strong variations in the impedance boundary conditions between the free field and surface wave regimes under certain experimental conditions. By systematically varying these impedance boundary conditions using different surface wave excitation techniques, we demonstrate that increased Rayleigh scattering and diffractive excitation can increase the dispersed surface wave pressure amplitude to an extent that the impedance-based wave suppression is circumvented. The improved conditions for observing acoustic Dirac points for two samples with two distinct operational frequency ranges are reported. The single-layer acoustic graphene analogue results discussed here are important for advancing the field of acoustic twistronics.
Journal of the Acoustical Society of America, Apr 1, 2022
This work presents a numerical study conducted on atmospheric sound propagation over sea. In part... more This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different seastates. Water roughness is pseudo-randomly generated using Pierson-Moskovitz ocean wave spectrum. Building on a previous result that has established a simple expression for predicting single frequency sound transmission loss as a function of sea state, this work extends the approach to broadband signal from 125 to 1000 Hz. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 1000 m from the source. These relationships are presented for typical nocturnal thermal gradients and for different elevations from the water surface.
Journal of the Acoustical Society of America, Apr 1, 2022
The purpose of this work is to understand the results obtained with the ANSI/ASA S1.18 standard f... more The purpose of this work is to understand the results obtained with the ANSI/ASA S1.18 standard for outdoor acoustic surface impedance measurements when applied to surfaces with characteristics at or outside the recommended use case. This study is part of a larger effort working to develop a numerical model for long-range atmospheric acoustic transmission loss over coastal areas. Previous studies were done to characterize the relationship between moisture content and effective flow resistivity of sandy shores by conducting acoustic surface impedance measurements following the procedure specified in the ANSI/ASA S1.18. While the standard specifies surface variation of less than 5 cm and at least four measurements per location, this work seeks to understand the consequences of surface variation in natural terrains on the obtained results. These consequences were evaluated by measuring the effective flow resistivity of multiple outdoor surfaces such as uniform grass, raked sandy shores, and undisturbed sandy shores. At every location, 16 measurements were performed in grid pattern. Subsets of the 16 measurements are used to perform an analysis of the variance of the measured flow resistivities collected at locations with different surface characteristics.
Journal of the Acoustical Society of America, Mar 1, 2023
This work presents atmospheric sound propagation predictions using a parabolic equation solver th... more This work presents atmospheric sound propagation predictions using a parabolic equation solver that accounts for heterogeneous wind profile distribution along the acoustic path. Transmission loss predictions using both homogeneous and heterogeneous wind speeds information are compared with data. A three-dimensional scanning Doppler LIDAR wind profiler captures real-time wind speed gradients at many locations along the acoustic propagation path providing the heterogeneous wind speed profiles. The wind measurements are concurrent with a pitch catch transmission loss measurements. A long-range acoustic device on an anchored pontoon sends known chirp sequences to a seven-channel receiver array at the water’s edge at ranges up to approximately one kilometer. Additional synchronized meteorological observations include temperature, humidity, and wind measured with anemometers. Key differences in model results are highlighted and an assessment of the value of the computational cost is presented.
Journal of the Acoustical Society of America, Oct 1, 2021
This work presents a numerical study conducted on atmospheric sound propagation over sea. In part... more This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different sea states. Water roughness is pseudo-randomly generated using an ocean wave spectrum. The GTPE predictions are compared with those obtained using the Crank-Nicholson parabolic equation (CNPE) solver. When using the CNPE the sea surface is flat and has a surface impedance equivalent to that of a rough surface. The use of the GTPE is less computationally efficient but provides insight on the detectability of an acoustic source at sea. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 500 m from the source. These relationships are presented for typical diurnal and nocturnal thermal gradients and for different elevations from the water surface.
Journal of the Acoustical Society of America, Apr 1, 2016
Extension of the two-microphone transfer function absorption coefficient measurement technique fr... more Extension of the two-microphone transfer function absorption coefficient measurement technique from impedance tubes to the free field introduces several error sources. The three-dimensional nature of the sound field necessitates consideration of factors that are not relevant in an enclosed tube below the cutoff frequency. The impedance tube technique has been modified to account for non-planar wave propagation due to an acoustic point source. The sound field contamination from sample edge diffraction has generally restricted use of the technique to frequencies such that wavelengths are small relative to sample dimensions. This requires the use of very large test panels for low frequencies. Numerical models of the two-microphone free field technique have been created to quantify these effects. Each effect was isolated to better understand its independent impact on the accuracy of the technique. Finally, a series of experimental tests were conducted to validate the numerical modeling results.
Journal of the Acoustical Society of America, Oct 1, 2017
Coupled oscillator systems can be designed to manage the distribution of mechanical energy in vib... more Coupled oscillator systems can be designed to manage the distribution of mechanical energy in vibration or acoustic systems. A specific implementation of an array composed of small damped mass-spring attachments on a primary is here referred to as a subordinate oscillator array. SOAs and their ability to absorb energy from a primary mass are of continued importance in analysis for both structural and acoustic systems. The ability to dissipate energy in a specific frequency band has many potential applications. This work will use laser Doppler vibrometry (LDV) to evaluate a beam mounted on an electromechanical shaker with and without an attached planar SOA composed of much smaller beams. This study is motivated by earlier work that indicated a high sensitivity to disorder in the form of fabrication error. The apparatus allows for the controlled introduction of various levels of disorder to quantify its effect and compare to a numerical model. We will show full-field forced response from the LDV with and without the SOA and the resulting apparent damping within the band of the SOA for various levels of disorder.
Journal of the Acoustical Society of America, May 1, 2017
The two-microphone transfer function technique of measuring absorption coefficient in a free fiel... more The two-microphone transfer function technique of measuring absorption coefficient in a free field has remained unchanged since its development in the 1980s. The free field technique has remained scarcely used due to usage restrictions caused by sound field contributions from diffraction of the test sample edge. Currently, the technique is only valid for instances where field contributions from edge diffraction is sufficiently minimized. This research uses acoustic numerical modeling to study the effects of error sources on the technique. Numerical models have been developed and used to quantify the effects of “image source deviation” and edge diffraction on the implementation of the free field technique. Each error source is quantified independently. Updated guidance on the usage restrictions of the free field technique is provided. Additionally, an improvement to the free field technique using a correction method is proposed. An experimental validation of the correction method was performed. The correction method showed improvement to the current two-microphone free field technique for higher frequencies (> 800 Hz) for samples 9” and larger as long as the nearest microphone location is no more than 16.7% of the sample width.
The Journal of the Acoustical Society of America, 2017
This presentation describes a student project that aims to study the effect of a guitar top’s mat... more This presentation describes a student project that aims to study the effect of a guitar top’s material and bracing design on measurable parameters such as radiated sound power and spectrum. To illustrate, two identical, classical guitars were purchased, and the soundboards were replaced. The top of one guitar was replaced with a soundboard composed of two different woods and the other with a carbon fiber composite. Mahogany and spruce were chosen as the two woods, as mahogany is purported to enhance lower notes and spruce to enhance higher notes. Carbon fiber was picked to maximize flexural rigidity of the top. Performances of the two guitars were characterized by measuring the acoustic pressure at a fixed distance from the guitar. Additionally, the vertical acceleration of specific locations of the top was also measured as well as the strain in the pick to make a fair comparison between the sounds radiated by both guitars. Sound recordings were analyzed with time-domain, frequency ...
Pm&r, Sep 1, 2014
To correlate electrodiagnostic (EDX) variables and clinical severity assessment with Disabilities... more To correlate electrodiagnostic (EDX) variables and clinical severity assessment with Disabilities of Arm, Shoulder & Hand (DASH) scores and to measure change over time with corresponding change in DASH scores. Design: Prospective Single Group Cohort, Pre-Post Design. Setting: Hospital-based electrodiagnostic clinic. Participants: 41 consecutive patients consented to participate and were invited to return for repeat study. Interventions: All subjects underwent EDX study and completed DASH. Data included: median sensory, mixed and motor latencies, amplitudes, conduction velocities and needle EMG. Main Outcome Measures: Paired samples t test was performed for change in DASH score over time. Results or Clinical Course: 41 subjects (6 female) enrolled. 6 rated as severe, 23 moderate and 12 mild CTS (NS). Mean DASH score [95 % C.I.] at start: 36.4 [30.5, 42.2]; final DASH score: 35.3 [27.1, 43.5], thus no significant change (t ¼ .293, df ¼ 27, p¼ .772). 26 subjects returned for their repeat study. Initial DASH score showed significant negative correlation with age: r ¼-0.379, p < .05), but no significant correlation with time interval between measurements: r ¼-0.047, p ¼ .82). Principal components analysis was used to reduce the large number of EDX variables which explained 73.5% of the cumulative variance. None of the EDX variables alone or in combination gave statistically significant correlation with the change in DASH score over time. Conclusions: This prospective cohort study attempted to examine influence of electrodiagnostic parameters on the self-reported disability and outcome using the DASH instrument. Significant drop-out (2nd visit) reduced the power to detect a meaningful difference. Our results showed no significant avg. change in DASH score over the time interval between visits. DASH showed a significant negative correlation with age of subject. Individual EDX did not predict change in DASH score over time.
Journal of the Acoustical Society of America, Sep 30, 2023
Journal of the Acoustical Society of America, Sep 30, 2023
Physical review, Aug 12, 2022
Dirac points in the band structure of acoustic systems are essential features affording classical... more Dirac points in the band structure of acoustic systems are essential features affording classical analogs of quantum condensed matter states. We show that measured dispersion curves near and at the Dirac point of an acoustic graphene analog can be suppressed by strong variations in the impedance boundary between free field and surface wave regimes under certain conditions. Increased Rayleigh scattering and diffractive excitation are shown to increase the dispersed surface wave pressure amplitude, circumventing the impedance-based wave suppression. The improved excitation and scattering conditions for observing acoustic Dirac points for two samples with two distinct operational frequency ranges are reported.
Proceedings of Meetings on Acoustics, 2020
This work presents a comparison between existing simple atmospheric temperature models and experi... more This work presents a comparison between existing simple atmospheric temperature models and experimental measurements of the lower atmospheric boundary layer. This work is part of a larger project developing an improved numerical model of atmospheric acoustic propagation in littoral or riverine environments with a near-shore acoustic source and on-shore receivers. In this study, temperature, humidity, and pressure data are collected with the use of sensors mounted on an unmanned aerial vehicle. Vertical measured temperature profiles are compared to existing common models and assumptions to gain a better understanding of how sufficient these models are at representing the meteorological parameters that will affect acoustic transmission. Representative transmission loss case studies comparing measured and model temperature profiles are included. Temperature profiles that do not represent the observed very near surface warming present in the case study lead to predicted transmission loss values differing by up to 15 dB over a 300 m range.
Journal of the Acoustical Society of America, Sep 1, 2018
The development of various propagation ducting phenomena (elevated or surface) has been studied e... more The development of various propagation ducting phenomena (elevated or surface) has been studied extensively for electromagnetic and electro-optical wave propagation. The influence of changes in temperature, pressure, and humidity gradients on the strength and geometry of the duct in the electromagnetic propagation problem is well-documented, and there is substantial literature regarding the influence of temperature gradient on atmospheric acoustic propagation. Analytical results indicate that moisture gradients in warm air above a sea surface contribute meaningfully to the refraction of sound. This work uses numerical simulation to explore the atmospheric conditions that would support development of acoustic ducts or wave guide conditions during moderate range (<1 km) acoustic propagation. The aim of this overall effort is an improved numerical model of acoustic refraction and attenuation over moderate to long distances above a sea surface that accounts for sea state as well as boundary layer wind, temperature, and humidity profiles.
Journal of the Acoustical Society of America, Oct 1, 2019
This work will investigate two non-destructive methods of fault detection in laminate structures ... more This work will investigate two non-destructive methods of fault detection in laminate structures such as frescos. These two techniques are compared on a purpose-built laboratory prototype and on frescos in the Senate Reception Room of the U.S. Capitol Building. Thermography uses an infrared camera to map the surface temperature of an object. This technique can be used to quickly identify abnormally hot or cold regions on a surface. These abnormal regions can indicate structural defects such as fresco delamination, cracks, and inclusions. The other non-destructive technique for defect detection used in this work is laser Doppler vibrometry paired with acoustic excitation of the target surface. Over the same surface area, thermography provides a much quicker result. This work aims to evaluate potential synergy between the technologies by comparing the results of the two scans. A prototype with known defects is used to find commonality between the two methods and to understand the circumstances in which the results diverge. The prototype is a square of approximately half a meter on each side. A seven centimeter thick concrete backing layer is followed by a layer of mortared antique bricks and topped by mortar and plaster to mimic fresco.
Journal of the Acoustical Society of America, Oct 1, 2014
The two-microphone transfer function method has become the most widely used method of impedance t... more The two-microphone transfer function method has become the most widely used method of impedance tube testing. Due to its measurement speed and ease of implementation, it has surpassed the standing-wave ratio method in popularity despite inherent frequency limitations due to tube geometry. Currently, the two-microphone technique is described in test standards ASTM E1050 and ISO 10534-2 to ensure accurate measurement. However, while detailed for correct test execution, the standards contain vague recommendations for a variety of measurement parameters. For instance, it is only stated in ASTM E1050 that “tube construction shall be massive so sound transmission through the tube wall is negligible.” To quantify this requirement, damping of the tube was varied to determine how different loss factor values effect measured absorption coefficient values. Additional sources of error explored are the amount of required absorbing material within the tube for reflective material measurements, additional calibration methods needed for test of excessive reflective materials, and alternate methods of combating microphone phase error and tube attenuation.
Applied Acoustics, Oct 1, 2022
Journal of the Acoustical Society of America, Mar 1, 2023
Journal of the Acoustical Society of America, Mar 1, 2023
There are many factors that must be considered in the study of atmospheric sound propagation over... more There are many factors that must be considered in the study of atmospheric sound propagation over long distances; these include surface characteristics as well as wind speed and air temperature profiles. This work presents measurements of air temperature profiles over various surfaces. Building a catalogue of this type can enable more realistic case assumptions to be made in an atmospheric acoustic transmission loss model. Accurate air temperature profiles are critical because of the potentially significant impact on the transmission loss predictions. Air temperature profile measurements have been collected by solar radiation shielded temperature loggers mounted 1 m apart on a 7 m mast. Long duration measurements were taken to capture the variability in day and nighttime temperature differentials present over surfaces such as: gravel, vegetated shoreline, marsh grass, lawn grass, water, and asphalt. In particular, measurements performed off shore were done by placing the sensor array on the deck of a pontoon boat. The initial results revealed that this configuration captures a very low elevation warming due to re-radiation from the deck of a boat instead of the true over water temperature. This study highlights the influence of wind speed on the development of the near surface temperature inversions.
Journal of the Acoustical Society of America, Mar 1, 2023
The dispersion of bound acoustic surface waves over hexagonal lattices of resonant cavities has b... more The dispersion of bound acoustic surface waves over hexagonal lattices of resonant cavities has been shown to be analogous to the dispersion of charge transport in carbon graphene. Of particular interest is the frequency range close to the acoustic Dirac point where novel physics is predicted to occur. In this study, we measure the dispersion curves of a single-layer acoustic graphene analogue with high resolution one-dimensional spatial scansand show how the curves can be suppressed (near and at the Dirac point) by strong variations in the impedance boundary conditions between the free field and surface wave regimes under certain experimental conditions. By systematically varying these impedance boundary conditions using different surface wave excitation techniques, we demonstrate that increased Rayleigh scattering and diffractive excitation can increase the dispersed surface wave pressure amplitude to an extent that the impedance-based wave suppression is circumvented. The improved conditions for observing acoustic Dirac points for two samples with two distinct operational frequency ranges are reported. The single-layer acoustic graphene analogue results discussed here are important for advancing the field of acoustic twistronics.
Journal of the Acoustical Society of America, Apr 1, 2022
This work presents a numerical study conducted on atmospheric sound propagation over sea. In part... more This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different seastates. Water roughness is pseudo-randomly generated using Pierson-Moskovitz ocean wave spectrum. Building on a previous result that has established a simple expression for predicting single frequency sound transmission loss as a function of sea state, this work extends the approach to broadband signal from 125 to 1000 Hz. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 1000 m from the source. These relationships are presented for typical nocturnal thermal gradients and for different elevations from the water surface.
Journal of the Acoustical Society of America, Apr 1, 2022
The purpose of this work is to understand the results obtained with the ANSI/ASA S1.18 standard f... more The purpose of this work is to understand the results obtained with the ANSI/ASA S1.18 standard for outdoor acoustic surface impedance measurements when applied to surfaces with characteristics at or outside the recommended use case. This study is part of a larger effort working to develop a numerical model for long-range atmospheric acoustic transmission loss over coastal areas. Previous studies were done to characterize the relationship between moisture content and effective flow resistivity of sandy shores by conducting acoustic surface impedance measurements following the procedure specified in the ANSI/ASA S1.18. While the standard specifies surface variation of less than 5 cm and at least four measurements per location, this work seeks to understand the consequences of surface variation in natural terrains on the obtained results. These consequences were evaluated by measuring the effective flow resistivity of multiple outdoor surfaces such as uniform grass, raked sandy shores, and undisturbed sandy shores. At every location, 16 measurements were performed in grid pattern. Subsets of the 16 measurements are used to perform an analysis of the variance of the measured flow resistivities collected at locations with different surface characteristics.
Journal of the Acoustical Society of America, Mar 1, 2023
This work presents atmospheric sound propagation predictions using a parabolic equation solver th... more This work presents atmospheric sound propagation predictions using a parabolic equation solver that accounts for heterogeneous wind profile distribution along the acoustic path. Transmission loss predictions using both homogeneous and heterogeneous wind speeds information are compared with data. A three-dimensional scanning Doppler LIDAR wind profiler captures real-time wind speed gradients at many locations along the acoustic propagation path providing the heterogeneous wind speed profiles. The wind measurements are concurrent with a pitch catch transmission loss measurements. A long-range acoustic device on an anchored pontoon sends known chirp sequences to a seven-channel receiver array at the water’s edge at ranges up to approximately one kilometer. Additional synchronized meteorological observations include temperature, humidity, and wind measured with anemometers. Key differences in model results are highlighted and an assessment of the value of the computational cost is presented.
Journal of the Acoustical Society of America, Oct 1, 2021
This work presents a numerical study conducted on atmospheric sound propagation over sea. In part... more This work presents a numerical study conducted on atmospheric sound propagation over sea. In particular, it focuses on the sound pressure level prediction uncertainties induced by the water surface roughness. To quantify these uncertainties, the generalized terrain parabolic equation (GTPE) is used to model sound propagation above water surfaces at different sea states. Water roughness is pseudo-randomly generated using an ocean wave spectrum. The GTPE predictions are compared with those obtained using the Crank-Nicholson parabolic equation (CNPE) solver. When using the CNPE the sea surface is flat and has a surface impedance equivalent to that of a rough surface. The use of the GTPE is less computationally efficient but provides insight on the detectability of an acoustic source at sea. This work presents relationships between fully developed sea states (up to sea state 4) and the uncertainties on sound pressure level predictions at distances up to 500 m from the source. These relationships are presented for typical diurnal and nocturnal thermal gradients and for different elevations from the water surface.
Journal of the Acoustical Society of America, Apr 1, 2016
Extension of the two-microphone transfer function absorption coefficient measurement technique fr... more Extension of the two-microphone transfer function absorption coefficient measurement technique from impedance tubes to the free field introduces several error sources. The three-dimensional nature of the sound field necessitates consideration of factors that are not relevant in an enclosed tube below the cutoff frequency. The impedance tube technique has been modified to account for non-planar wave propagation due to an acoustic point source. The sound field contamination from sample edge diffraction has generally restricted use of the technique to frequencies such that wavelengths are small relative to sample dimensions. This requires the use of very large test panels for low frequencies. Numerical models of the two-microphone free field technique have been created to quantify these effects. Each effect was isolated to better understand its independent impact on the accuracy of the technique. Finally, a series of experimental tests were conducted to validate the numerical modeling results.
Journal of the Acoustical Society of America, Oct 1, 2017
Coupled oscillator systems can be designed to manage the distribution of mechanical energy in vib... more Coupled oscillator systems can be designed to manage the distribution of mechanical energy in vibration or acoustic systems. A specific implementation of an array composed of small damped mass-spring attachments on a primary is here referred to as a subordinate oscillator array. SOAs and their ability to absorb energy from a primary mass are of continued importance in analysis for both structural and acoustic systems. The ability to dissipate energy in a specific frequency band has many potential applications. This work will use laser Doppler vibrometry (LDV) to evaluate a beam mounted on an electromechanical shaker with and without an attached planar SOA composed of much smaller beams. This study is motivated by earlier work that indicated a high sensitivity to disorder in the form of fabrication error. The apparatus allows for the controlled introduction of various levels of disorder to quantify its effect and compare to a numerical model. We will show full-field forced response from the LDV with and without the SOA and the resulting apparent damping within the band of the SOA for various levels of disorder.
Journal of the Acoustical Society of America, May 1, 2017
The two-microphone transfer function technique of measuring absorption coefficient in a free fiel... more The two-microphone transfer function technique of measuring absorption coefficient in a free field has remained unchanged since its development in the 1980s. The free field technique has remained scarcely used due to usage restrictions caused by sound field contributions from diffraction of the test sample edge. Currently, the technique is only valid for instances where field contributions from edge diffraction is sufficiently minimized. This research uses acoustic numerical modeling to study the effects of error sources on the technique. Numerical models have been developed and used to quantify the effects of “image source deviation” and edge diffraction on the implementation of the free field technique. Each error source is quantified independently. Updated guidance on the usage restrictions of the free field technique is provided. Additionally, an improvement to the free field technique using a correction method is proposed. An experimental validation of the correction method was performed. The correction method showed improvement to the current two-microphone free field technique for higher frequencies (> 800 Hz) for samples 9” and larger as long as the nearest microphone location is no more than 16.7% of the sample width.
The Journal of the Acoustical Society of America, 2017
This presentation describes a student project that aims to study the effect of a guitar top’s mat... more This presentation describes a student project that aims to study the effect of a guitar top’s material and bracing design on measurable parameters such as radiated sound power and spectrum. To illustrate, two identical, classical guitars were purchased, and the soundboards were replaced. The top of one guitar was replaced with a soundboard composed of two different woods and the other with a carbon fiber composite. Mahogany and spruce were chosen as the two woods, as mahogany is purported to enhance lower notes and spruce to enhance higher notes. Carbon fiber was picked to maximize flexural rigidity of the top. Performances of the two guitars were characterized by measuring the acoustic pressure at a fixed distance from the guitar. Additionally, the vertical acceleration of specific locations of the top was also measured as well as the strain in the pick to make a fair comparison between the sounds radiated by both guitars. Sound recordings were analyzed with time-domain, frequency ...
Pm&r, Sep 1, 2014
To correlate electrodiagnostic (EDX) variables and clinical severity assessment with Disabilities... more To correlate electrodiagnostic (EDX) variables and clinical severity assessment with Disabilities of Arm, Shoulder & Hand (DASH) scores and to measure change over time with corresponding change in DASH scores. Design: Prospective Single Group Cohort, Pre-Post Design. Setting: Hospital-based electrodiagnostic clinic. Participants: 41 consecutive patients consented to participate and were invited to return for repeat study. Interventions: All subjects underwent EDX study and completed DASH. Data included: median sensory, mixed and motor latencies, amplitudes, conduction velocities and needle EMG. Main Outcome Measures: Paired samples t test was performed for change in DASH score over time. Results or Clinical Course: 41 subjects (6 female) enrolled. 6 rated as severe, 23 moderate and 12 mild CTS (NS). Mean DASH score [95 % C.I.] at start: 36.4 [30.5, 42.2]; final DASH score: 35.3 [27.1, 43.5], thus no significant change (t ¼ .293, df ¼ 27, p¼ .772). 26 subjects returned for their repeat study. Initial DASH score showed significant negative correlation with age: r ¼-0.379, p < .05), but no significant correlation with time interval between measurements: r ¼-0.047, p ¼ .82). Principal components analysis was used to reduce the large number of EDX variables which explained 73.5% of the cumulative variance. None of the EDX variables alone or in combination gave statistically significant correlation with the change in DASH score over time. Conclusions: This prospective cohort study attempted to examine influence of electrodiagnostic parameters on the self-reported disability and outcome using the DASH instrument. Significant drop-out (2nd visit) reduced the power to detect a meaningful difference. Our results showed no significant avg. change in DASH score over the time interval between visits. DASH showed a significant negative correlation with age of subject. Individual EDX did not predict change in DASH score over time.