David Browning
University of California, Department, Emeritus
- Retired physicist (acoustics).edit
The principal mechanism for low frequency sound absorption in seawater is a boron relaxation reaction that is pH dependent: the lower the pH; the lower the absorption. In 1987, Mellen et al. [J. Acoust. Soc. Am. 82, S30 (1987)]... more
The principal mechanism for low frequency sound absorption in seawater is a boron relaxation reaction that is pH dependent: the lower the pH; the lower the absorption. In 1987, Mellen et al. [J. Acoust. Soc. Am. 82, S30 (1987)] extensively computed the low frequency absorption in the Arctic Ocean. Since that time the carbon dioxide (CO2) level in the atmosphere has been continually increasing, and in 2014 Browning and Herstein reported the corresponding change in ocean pH and resulting change in seawater sound absorption that had occurred [J. Acoust. Soc. Am. 135, 2306 (2014)]. This paper now provides a further update to the present time on the changing Arctic Ocean low frequency sound absorption and indicates what the result might beif the United Nations' goal of reaching equilibrium in 12 years is met.
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ABSTRACT In 1965, Thorp published a compilation of low frequency data from SOFAR propagation that indicated absorption below 10,000 Hz was greater than predicted. It was suggested this may be an artifact, but the data were shown to fit a... more
ABSTRACT In 1965, Thorp published a compilation of low frequency data from SOFAR propagation that indicated absorption below 10,000 Hz was greater than predicted. It was suggested this may be an artifact, but the data were shown to fit a 1 kHz relaxation mechanism. NUWC (formerly NUSC) began an extensive at-sea measurement program, ranging from Hudson Bay (jointly with Canadian DREP) to Lake Tanganyika, while several other laboratories obtained data in other oceans. Yeager and Fisher, using the T-jump method at the Case-Western Laboratory, determined there was a 1 kHz relaxation in seawater associated with boron. The data collected at-sea showed, however, a variation between ocean areas, notably values from the North Pacific were 1/2 those in the North Atlantic. This puzzled supporters and encouraged critics. At Scripps, Simmons and Fisher, using a resonating sphere, showed that the boron relaxation did indeed cause the absorption of low frequency sound. Browning and Mellen discovered the key to the at-sea variation was pH, and at NUWC Mellen confirmed this dependence in the laboratory using Simmons' sphere. This direct connection between low frequency absorption and ocean acidification has produced several recent papers on possible implications, and increasing global warming suggests an interesting future.
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ABSTRACT In 1965, Thorp published a compilation of low frequency data from SOFAR propagation that indicated absorption below 10,000 Hz was greater than predicted. It was suggested this may be an artifact, but the data were shown to fit a... more
ABSTRACT In 1965, Thorp published a compilation of low frequency data from SOFAR propagation that indicated absorption below 10,000 Hz was greater than predicted. It was suggested this may be an artifact, but the data were shown to fit a 1 kHz relaxation mechanism. NUWC (formerly NUSC) began an extensive at-sea measurement program, ranging from Hudson Bay (jointly with Canadian DREP) to Lake Tanganyika, while several other laboratories obtained data in other oceans. Yeager and Fisher, using the T-jump method at the Case-Western Laboratory, determined there was a 1 kHz relaxation in seawater associated with boron. The data collected at-sea showed, however, a variation between ocean areas, notably values from the North Pacific were 1/2 those in the North Atlantic. This puzzled supporters and encouraged critics. At Scripps, Simmons and Fisher, using a resonating sphere, showed that the boron relaxation did indeed cause the absorption of low frequency sound. Browning and Mellen discovered the key to the at-sea variation was pH, and at NUWC Mellen confirmed this dependence in the laboratory using Simmons' sphere. This direct connection between low frequency absorption and ocean acidification has produced several recent papers on possible implications, and increasing global warming suggests an interesting future.
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ABSTRACT The attenuation of low-frequency sound in the sea increases with pH. In most ocean areas, the value of pH changes significantly with depth, and must be included in an accurate attenuation computation. Previous determinations of... more
ABSTRACT The attenuation of low-frequency sound in the sea increases with pH. In most ocean areas, the value of pH changes significantly with depth, and must be included in an accurate attenuation computation. Previous determinations of other parameters, such as surface loss, which were based on older attenuation formulas, are therefore inaccurate. An analysis of a previously reported surface loss formula indicates that the predicted values are too high
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ABSTRACT The attenuation of low-frequency sound in the sea increases with pH. In most ocean areas, the value of pH changes significantly with depth, and must be included in an accurate attenuation computation. Previous determinations of... more
ABSTRACT The attenuation of low-frequency sound in the sea increases with pH. In most ocean areas, the value of pH changes significantly with depth, and must be included in an accurate attenuation computation. Previous determinations of other parameters, such as surface loss, which were based on older attenuation formulas, are therefore inaccurate. An analysis of a previously reported surface loss formula indicates that the predicted values are too high
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The "fog-bound" coast of New England has posed a hazard to all forms of transportation for centuries, yet relatively little study, especially in recent times, has been done on the physics of fog. The singular study of sound... more
The "fog-bound" coast of New England has posed a hazard to all forms of transportation for centuries, yet relatively little study, especially in recent times, has been done on the physics of fog. The singular study of sound propagation, conducted in 1959, found no apparent increase over the normal frequency dependent absorption in air. However, a recent text (W. Binhua, SEA FOG, Springer-Verlag, 1985) indicates that this was only a moderate fog and not the much more intense ("killer") fogs. For these the aggregaton of water droplets may lead to increased low frequency absorption thus reducing the effective range of existing foghorns. On land, advances in light scattering might be applied to provide a simple mobile means (mounted on a police car, for example) to quickly identify extreme conditions and take precautionary action on the highway to prevent the horrific multi-car collisions that can occur.
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The "fog-bound" coast of New England has posed a hazard to all forms of transportation for centuries, yet relatively little study, especially in recent times, has been done on the physics of fog. The singular study of sound... more
The "fog-bound" coast of New England has posed a hazard to all forms of transportation for centuries, yet relatively little study, especially in recent times, has been done on the physics of fog. The singular study of sound propagation, conducted in 1959, found no apparent increase over the normal frequency dependent absorption in air. However, a recent text (W. Binhua, SEA FOG, Springer-Verlag, 1985) indicates that this was only a moderate fog and not the much more intense ("killer") fogs. For these the aggregaton of water droplets may lead to increased low frequency absorption thus reducing the effective range of existing foghorns. On land, advances in light scattering might be applied to provide a simple mobile means (mounted on a police car, for example) to quickly identify extreme conditions and take precautionary action on the highway to prevent the horrific multi-car collisions that can occur.
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Ionic relaxations involving magnesium sulfate, boric acid and magnesium, carbonate are known to account for sound absorption in sea water. Regional dependence of sound absorption has been shown to be caused mainly by the pH-dependence of... more
Ionic relaxations involving magnesium sulfate, boric acid and magnesium, carbonate are known to account for sound absorption in sea water. Regional dependence of sound absorption has been shown to be caused mainly by the pH-dependence of the boric acid relaxation. In the nominal sea water pH range 7.7-8.3, the magnitude can be expected to vary over neatly a factor of four at lower frequencies. Since pH varies with depth as well as locations, net absorption will also depend on the ray paths. An interim global model, based on published pH contours for the World Ocean, has been proposed. Correction factors for the sound-channel, convergence-zone and surface-duct modes are provided by individual contour charts. However, if there is no clearly dominant propagation mode, integrations of loss over all ray paths may be indicated, which requires profiles of correction-factor vs depth. Part-2 reports analysis of pH data obtained during the GEOSECS expeditions 1972-1978. The purpose is to chec...
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Ionic relaxations involving magnesium sulfate, boric acid and magnesium, carbonate are known to account for sound absorption in sea water. Regional dependence of sound absorption has been shown to be caused mainly by the pH-dependence of... more
Ionic relaxations involving magnesium sulfate, boric acid and magnesium, carbonate are known to account for sound absorption in sea water. Regional dependence of sound absorption has been shown to be caused mainly by the pH-dependence of the boric acid relaxation. In the nominal sea water pH range 7.7-8.3, the magnitude can be expected to vary over neatly a factor of four at lower frequencies. Since pH varies with depth as well as locations, net absorption will also depend on the ray paths. An interim global model, based on published pH contours for the World Ocean, has been proposed. Correction factors for the sound-channel, convergence-zone and surface-duct modes are provided by individual contour charts. However, if there is no clearly dominant propagation mode, integrations of loss over all ray paths may be indicated, which requires profiles of correction-factor vs depth. Part-2 reports analysis of pH data obtained during the GEOSECS expeditions 1972-1978. The purpose is to chec...
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This report examines the impact of the model on sonar performance and the surface and bottom-loss models upon which predictions are currently based. The present analysis is limited mainly to active systems operating in the frequency range... more
This report examines the impact of the model on sonar performance and the surface and bottom-loss models upon which predictions are currently based. The present analysis is limited mainly to active systems operating in the frequency range 3-4 kHz. The four regions examined are: North Atlantic, North Pacific, Eastern Mediterranean and Norwegian Sea. Comparison of K model predictions with those based on the Thorp formula indicates that two-way path absorption for the first CZ zone ranges from approximately 4 dB less in the North Pacific to 12 dB greater in the Eastern Mediterranean. In the bottom- bounce mode, these values are reduced roughly in proportion to range. The MGS bottom-loss model is based on analysis of one-way paths using the Thorp formula. The difference between the K model and Thorp formula for 10 degree grazing angle in the Eastern Mediterranean is roughly 4 bB, making the actual bottom-loss smaller by about on province number. the differences decrease with increasing ...
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This report examines the impact of the model on sonar performance and the surface and bottom-loss models upon which predictions are currently based. The present analysis is limited mainly to active systems operating in the frequency range... more
This report examines the impact of the model on sonar performance and the surface and bottom-loss models upon which predictions are currently based. The present analysis is limited mainly to active systems operating in the frequency range 3-4 kHz. The four regions examined are: North Atlantic, North Pacific, Eastern Mediterranean and Norwegian Sea. Comparison of K model predictions with those based on the Thorp formula indicates that two-way path absorption for the first CZ zone ranges from approximately 4 dB less in the North Pacific to 12 dB greater in the Eastern Mediterranean. In the bottom- bounce mode, these values are reduced roughly in proportion to range. The MGS bottom-loss model is based on analysis of one-way paths using the Thorp formula. The difference between the K model and Thorp formula for 10 degree grazing angle in the Eastern Mediterranean is roughly 4 bB, making the actual bottom-loss smaller by about on province number. the differences decrease with increasing ...
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ABSTRACT A horse’s whinny appears to be a very interesting vocalization. Initial acoustic analysis suggested two principal components, one ‘‘emotional’’ and the other ‘‘expressive.’’ The first seems to follow Morton’s criterion:... more
ABSTRACT A horse’s whinny appears to be a very interesting vocalization. Initial acoustic analysis suggested two principal components, one ‘‘emotional’’ and the other ‘‘expressive.’’ The first seems to follow Morton’s criterion: increasing frequency with emotional state. The second component, since many suggest that a whinny is not a threatening gesture, has the potential for a number of specific expressions for such situations as ‘‘calling’’ or ‘‘greeting.’’ This paper describes the present indications as the data base slowly increases.
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ABSTRACT A horse’s whinny appears to be a very interesting vocalization. Initial acoustic analysis suggested two principal components, one ‘‘emotional’’ and the other ‘‘expressive.’’ The first seems to follow Morton’s criterion:... more
ABSTRACT A horse’s whinny appears to be a very interesting vocalization. Initial acoustic analysis suggested two principal components, one ‘‘emotional’’ and the other ‘‘expressive.’’ The first seems to follow Morton’s criterion: increasing frequency with emotional state. The second component, since many suggest that a whinny is not a threatening gesture, has the potential for a number of specific expressions for such situations as ‘‘calling’’ or ‘‘greeting.’’ This paper describes the present indications as the data base slowly increases.
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ABSTRACT Over multiple convergence zone propagation ranges the relative spreading loss per zone, although initially high, decreases with range. The other major component of propagation loss, attenuation, remains unchanged and eventually... more
ABSTRACT Over multiple convergence zone propagation ranges the relative spreading loss per zone, although initially high, decreases with range. The other major component of propagation loss, attenuation, remains unchanged and eventually becomes greater than the rate of spreading loss. The range at which this crossover occurs is highly frequency dependent. At low frequencies the curtain effect occurs at long ranges; this allows sources or scatterers in the second convergence zone or beyond to impact the received level since they suffer only a relatively small additional loss compared to the spreading loss to the first convergence zone. For a given distribution of noise source levels or scattering strengths it is estimated what would be the resulting background level and the relative importance of events, for example, a comparison between medium strength multiple events at medium ranges and a strong event at long range. This analysis is then extended to higher frequencies where the curtain effect occurs at a range of one convergence zone or less.
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ABSTRACT Over multiple convergence zone propagation ranges the relative spreading loss per zone, although initially high, decreases with range. The other major component of propagation loss, attenuation, remains unchanged and eventually... more
ABSTRACT Over multiple convergence zone propagation ranges the relative spreading loss per zone, although initially high, decreases with range. The other major component of propagation loss, attenuation, remains unchanged and eventually becomes greater than the rate of spreading loss. The range at which this crossover occurs is highly frequency dependent. At low frequencies the curtain effect occurs at long ranges; this allows sources or scatterers in the second convergence zone or beyond to impact the received level since they suffer only a relatively small additional loss compared to the spreading loss to the first convergence zone. For a given distribution of noise source levels or scattering strengths it is estimated what would be the resulting background level and the relative importance of events, for example, a comparison between medium strength multiple events at medium ranges and a strong event at long range. This analysis is then extended to higher frequencies where the curtain effect occurs at a range of one convergence zone or less.
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ABSTRACT The observed relationship between wind speed and ambient noise level has varied from ocean to ocean. Generally higher levels measured in southern hemisphere oceans have been attributed to fully developed seas, although this... more
ABSTRACT The observed relationship between wind speed and ambient noise level has varied from ocean to ocean. Generally higher levels measured in southern hemisphere oceans have been attributed to fully developed seas, although this mechanism is not understood. Ambient noise data taken near Bermuda after a persistent (5 days) wind of approximately 40 knots are higher than previously observed and consistent with southern ocean measurements, thus supporting a developed sea state hypothesis. (jhd)
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ABSTRACT The observed relationship between wind speed and ambient noise level has varied from ocean to ocean. Generally higher levels measured in southern hemisphere oceans have been attributed to fully developed seas, although this... more
ABSTRACT The observed relationship between wind speed and ambient noise level has varied from ocean to ocean. Generally higher levels measured in southern hemisphere oceans have been attributed to fully developed seas, although this mechanism is not understood. Ambient noise data taken near Bermuda after a persistent (5 days) wind of approximately 40 knots are higher than previously observed and consistent with southern ocean measurements, thus supporting a developed sea state hypothesis. (jhd)
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ABSTRACT Measurements of ambient noise (30-800 Hz) useful in characterizing the wind-generated component have been obtained in the low ship density Southern Hemisphere. Source levels that characterize the frequency and wind speed... more
ABSTRACT Measurements of ambient noise (30-800 Hz) useful in characterizing the wind-generated component have been obtained in the low ship density Southern Hemisphere. Source levels that characterize the frequency and wind speed dependence of this noise have been obtained by Burgess and Kewley using vertical noise dirctionality data and had been implemented in a diagnostic computerized noise model. Northern Hemisphere vertical noise directionality data have been examined, processed for source level, and compared to these results. These data and other data summaries, when taking a two-mechanism viewpoint, are found to be consistent with respect to wind speed and frequency dependence. When a dipole source model, based on the possible physical mechanism of sound production, is used, a set of consistent source levels for wind-dependent noise is realized from the several data sets examined.
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ABSTRACT Measurements of ambient noise (30-800 Hz) useful in characterizing the wind-generated component have been obtained in the low ship density Southern Hemisphere. Source levels that characterize the frequency and wind speed... more
ABSTRACT Measurements of ambient noise (30-800 Hz) useful in characterizing the wind-generated component have been obtained in the low ship density Southern Hemisphere. Source levels that characterize the frequency and wind speed dependence of this noise have been obtained by Burgess and Kewley using vertical noise dirctionality data and had been implemented in a diagnostic computerized noise model. Northern Hemisphere vertical noise directionality data have been examined, processed for source level, and compared to these results. These data and other data summaries, when taking a two-mechanism viewpoint, are found to be consistent with respect to wind speed and frequency dependence. When a dipole source model, based on the possible physical mechanism of sound production, is used, a set of consistent source levels for wind-dependent noise is realized from the several data sets examined.
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ABSTRACT Low-frequency, wind-generated ambient noise source levels are important input parameters for newly developed ambient noise prediction models such as DUNES. However, there has been a significant variation among recently reported... more
ABSTRACT Low-frequency, wind-generated ambient noise source levels are important input parameters for newly developed ambient noise prediction models such as DUNES. However, there has been a significant variation among recently reported source levels. An analysis is made of these values. Although the actual noise measurements, the assumed source model, and a small angle approximation are similar for all papers; differences arise due to additional geometrical factors or a further approximation to shift the source level to the surface. A standard source level definition and an evaluation method are proposed. Standard values of low-frequency, wind-generated source levels are presented based on this strategy. Keywords: Low-frequency ambient noise, Mathematical prediction, Mathematical models, Acoustic data standardization, Underwater acoustics, Ambient noise source levels.
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ABSTRACT Low-frequency, wind-generated ambient noise source levels are important input parameters for newly developed ambient noise prediction models such as DUNES. However, there has been a significant variation among recently reported... more
ABSTRACT Low-frequency, wind-generated ambient noise source levels are important input parameters for newly developed ambient noise prediction models such as DUNES. However, there has been a significant variation among recently reported source levels. An analysis is made of these values. Although the actual noise measurements, the assumed source model, and a small angle approximation are similar for all papers; differences arise due to additional geometrical factors or a further approximation to shift the source level to the surface. A standard source level definition and an evaluation method are proposed. Standard values of low-frequency, wind-generated source levels are presented based on this strategy. Keywords: Low-frequency ambient noise, Mathematical prediction, Mathematical models, Acoustic data standardization, Underwater acoustics, Ambient noise source levels.