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An earlier study examined the effects of exposure to seismic air guns on the hearing of three species of fish from the Mackenzie River Delta in Northern Canada [Popper et al. (2005). "Effects of exposure to seismic airgun use on hearing of three fish species," J. Acoust. Soc. Am. 117, 3958-3971]. The sound pressure levels to which the fishes were exposed were a mean received level of 205-209 dB re 1 microPa (peak) per shot and an approximate received mean SEL of 176-180 dB re 1 microPa(2) s per shot. In this report, the same animals were examined to determine whether there were effects on the sensory cells of the inner ear as a result of the seismic exposure. No damage was found to the ears of the fishes exposed to seismic sounds despite the fact that two of the species, adult northern pike and lake chub, had shown a temporary threshold shift in hearing studies.

In May 2013 we performed a series of seventy explosion tests, varying the mass, shape, and height of the explosives. Shots were comprised of 11.6 kg, 4.9 kg, and 1.7 kg cylinders and 14.9 kg spheres, all of Comp-B. Explosive heights varied between 4, 2, 1, and 1/2 m above the surface, at the surface, and buried 1 m below the surface. Explosives above the surface were suspended by rope between two concrete pillars. In addition, ground surfaces were altered between dry sand, chicken wire, and concrete blocks. We monitored the explosions on 13 acoustic stations. Four temporary stations were deployed surrounding the shot site at less than 1 km distance. Eight additional stations were at distances of 1 to less than 9 km, and one at ~23 km from the shot site, 4 of which were temporary stations, and 5 are part of the Los Alamos Seismo-acoustic Network. We report on a detailed analysis of signal differences related to explosive and meteorological variations. The large quantity of data from repeating shots enables...

An archery bow shot cover device is attachable to an archery bow for use during hunting an animal. The archery bow shot cover device includes a housing, a sensor, a memory chip and a speaker. During use, a sensor detects the release of an arrow from the archery bow, which triggers a memory chip to send a signal carrying an animal sound to the speaker. The animal sound is emanated from the speaker and covers up or camouflages the noise produced by the release of the arrow from the bow. The sensor may be an accelerometer or other vibration type of switch, a motion detector, a bar code type of reader, or other type of sensor for detecting the release of the arrow from the archery bow. The device includes a USB port or jack for installing additional natural animal sounds or other types of sounds onto the device.

The Littoral Acoustic Demonstration Center (LADC) recorded acoustic and related data on three moored arrays and ship‐deployed hydrophones, which together spanned the full water column to measure the 3‐D acoustic field of a seismic airgun array, in September 2007. The seismic source vessel shot specified lines to give detailed solid angle and range information concerning the field of the primary arrival. The data were collected in the western Gulf of Mexico between the East Break and Alamos Canyon regions. Peak pressures, sound exposure levels, total shot energy spectra, one‐third octave band analyzes, and source directivity studies are used to characterize the field. Three‐dimensional maps of these quantities are generated to show dependence on emission and azimuthal angles and range. Longer lines were shot for propagation analyzes. Source signatures from NUCLEUS and GUNDALF are used in propagation modeling. [Research supported by the Joint Industry Programme through the International Association of Oil a...

The Source Characterization Study 2007 (SCS07) measured the three‐dimensional (3‐D) acoustic field of a seismic airgun array. The Littoral Acoustic Demonstration Center (LADC) performed the experiment, collecting acoustic and related data on three moored hydrophone arrays and one ship‐deployed hydrophone array which together spanned the full water column. Sensitive and desensitized phones were deployed at each position to extend the dynamic range. An ultra short baseline localization system was deployed with the EARS moorings to provide array shape. With postanalysis this results in time‐dependent positions for each of the acoustic sensors. Every channel is calibrated. A seismic source vessel shot a series of lines designed to give detailed angle and range information concerning the field of the primary arrival. Peak pressures, sound exposure levels, total shot energy spectra, and one‐third octave band analyses give important insights into details of the acoustic field. Images of these quantities are gene...

The Source Characterization Study 2007 measured the three‐dimensional acoustic field of a seismic airgun array. The Littoral Acoustic Demonstration Center performed the experiment, collecting acoustic and related data on three moored hydrophone arrays and one ship‐deployed hydrophone array which together spanned the full water column. Sensitive and desensitized phones were deployed at each position to extend the dynamic range. An ultra short baseline localization system was deployed with the EARS moorings to provide array shape. With post analysis this results in time‐dependent positions for each of the acoustic sensors. Every channel is calibrated. A seismic source vessel shot a series of lines designed to give detailed angle and range information concerning the field of the primary arrival. The experiment was conducted in the western Gulf of Mexico between the East Break and Alamos Canyon regions. Peak pressures, sound exposure levels, total shot energy spectra, and one‐third octave band analyses are me...

In September 2007 the Littoral Acoustic Demonstration Center (LADC) collected acoustic and related data from three moored arrays and ship‐deployed hydrophones spanning the full water column to measure the three‐dimensional acoustic field of a seismic airgun array. The seismic source vessel shot a series of lines to give a detailed angle and range information concerning the field. The data were collected in the western Gulf of Mexico between the East Break and Alamos Canyon regions. Peak pressures, sound exposure levels, total shot energy spectra, and one‐third octave band analyses are measures used to characterize the field. Three dimensional maps of these quantities are generated to show dependence on emission and azimuthal angles and range. Both the direct and indirect fields are characterized. Moveout analysis is done to delineate arrivals and to detect ducted and interface waves. [Research supported by the International Association of Oil and Gas Producers.]

An electronic percussion instrument includes a vibration detection apparatus having a simplified frame structure that increases the uniformity of its rim shot strike sensitivity distribution. The frame is comprised of a flange, a center section and a linking section that surrounds the center section and extends from the center section to the flange. The flange engages the end of the drum body and the frame is disposed within the drum body. A rim shot sensor is mounted to the center section of the frame and detects rim shot vibrations that are transmitted through the frame. Because the linking section of the frame surrounds the center section, uniformity of rim shot strike sensitivity is improved. A head sensor is also mounted to the frame on a support plate that is coupled to the frame through a vibration isolating damper. A cushioning material is placed between the head sensor and a head of the percussion instrument for transmitting vibrations from the head to the head sensor. The flange of the frame and a drum head are held between an end of the drum body and a rim that is bolted to the drum body.

In the summer of 2003 two Environmental Acoustic Recording System (EARS) buoys were deployed in the northern Gulf of Mexico by the Littoral Acoustic Demonstration Center. The buoys were collocated and recorded ambient noise and seismic airgun array shots up to approximately 25 kHz. The gains and hydrophone sensitivities were set such that one EARS buoy could record the seismic shots without clipping and the other could record ambient noise. The M/V Kondor towed an airgun array on parallel linear tracks with horizontal closest points of approach to the buoy of 0, 500, 1000, 2000, and 5000 m, giving experimental data for a wide range of horizontal distances (up to 7 km) and arrival angles. The raw data were calibrated using the EARS system parameters to produce calibrated pressure time series for each shot. These data are analyzed in both the time and frequency domains. Maximum pressures for each shot as well as sound exposure levels (pressure squared integrated over time for 200 ms in this case) are presen...

A series of short‐range outdoor measurements was conducted to investigate forest effects on acoustic pulse propagation. The measurements investigated seven different forest stands with a variety of different tree species including deciduous, evergreen, and mixed. A 0.45‐caliber blank pistol shot was used as the source of the acoustic pulses, and the signatures were recorded 30 to 60 m away using a digital seismograph. An identical measurement was conducted in an open field for comparison. The recorded waveforms generally show the elongation characteristic of pulse propagation over a highly porous ground surface, with high‐frequency reverberation arrivals superimposed on the basic waveform shape. These measurements can provide parameters useful for theoretical predictions of acoustic propagation within forests, and also illustrate some of the natural variability encountered in these environments. [Work funded by U.S. Army.]

During the short‐range winter measurements at Haslemoen, Norway, a series of blast wave forms produced by 1‐kg charges of C4 explosive fired 2 m above a dry snow cover 11 to 20 cm thick were recorded after propagating horizontally 100 to 1400 m. In attempting to model these experiments, it was found that the usual viscoelastic treatment of the ground was unable to match the recorded wave forms. A rigid‐porous model of the snow cover was required to obtain good agreement. The measured wave forms, with a peak frequency around 50 Hz, show pulse broadening effects similar to those previously seen in pistol shot experiments using higher frequency waves over shorter propagation distances. The modeling predicts an average snow cover depth of 15 cm and effective flow resistivities of 30−41 kPa s m−2, in agreement with snow pit observations and with previous acoustic measurements over snow. For propagation in the upwind direction, the pulse broadening caused by the snow cover interaction is lessened, but the overall amplitude decay is greater because of refraction of the blast waves.

The shot‐to‐shot spatial variability of acoustic and cavitation fields of a spark‐source lithotripter was investigated. Spark jitter, variation in the arc strength and location is cited for lack of repeatability in laboratory experiments and is thought to contribute to the success of the Dornier HM3 in comminuting kidney stones, which tend to move during treatment. Transverse variability of the acoustic focus was assessed by measuring the location of the shock wave (SW) induced fountain. The water bath was lowered and a small cup half‐filled with ink and having a gridded paper roof was placed at the level of the focus. An ink drop created by the fountain was recorded on the paper. Drop diameter varied from 0–12 mm, location of its center varied by about 1 mm. The extent and location of the cavitation field was measured by high‐speed camera. The cavitation cluster was 1×10 cm at its largest extent but bubbles collapsed in a narrow 1–2 mm line. The location of the line was repeatable to within 2 mm. The results indicated that spark jitter affected SW amplitude but had little effect on the location of the acoustic axis. [Work supported by NIH (DK 43881), CRDF and RFBR.]

In order to identify and eliminate flawed ceramic preforms prior to metal infiltration, several approaches for nondestructive evaluation were studied. The techniques chosen include immersion ultrasonics, scanning acoustic microscopy (SAM), and radiography. Undesirable irregularities in the preforms include cracks, voids, density gradients, and shot. The latter represents spherically shaped particles of alumina, with diameters that may exceed ten times that of the fibers, and that are incorporated into the porous fiber preform. It is generally thought that shot with sizes greater than 100 μm affects the mechanical properties of the resulting metal matrix composite. With the aid of SAM and scanning electron microscopy (SEM), shot in near‐surface areas could be evaluated. Cracks and voids could also be located using SAM and SEM. On a larger scale, the ultrasonic immersion equipment was capable of detecting and quantifying density gradients, which were verified using radiographic techniques. Examples will be ...

A tomography system consisting of aircraft‐deployed shots as sources and a vertical line array moored by a receiver ship was used to survey a large area (120×120 km) where a mesoscale warm eddy appears frequently. The position of the shots was measured by the GPS on the aircraft and the detonation time (or depth) was monitored by sonobuoys which had been deployed close to the shot position. Results show that individual multipaths between a shot and the receiver contain substantial information for a vertical slice of the ocean with a warm eddy. With high accuracy, GPS positioning of shot locations, and receiver position, this rapidly deployable system can be used for monitoring the submerged structure of the warm eddy during the period of diffusive SST in summer in the East Sea of Korea. [Work supported by KOSEF.]

Disclosed is a hand-held percussion musical instrument in the form of a rigid tubular ring, which includes a plurality of elongate hollow tubes, the tubes having rigid tubular walls and opposite end walls defining closed hollow tube interiors. Steel shot is loosely contained within the hollow interiors of the tubes, whereby the ring may be hand manipulated to cause the shot to impact the walls to create audible percussion sounds.

Experimental measurements of acoustic impulses propagating horizontally above a seasonal snow cover reveal the presence of acoustic surface waves that were not observed under grass or frozen ground conditions. The measurements were obtained using blank pistol shots fired 1 m above the snow as the source of acoustic impulses; the resultant acoustic waveforms were measured by microphones at heights of from 0.1 to 4.75 m after 60 m of horizontal propagation along the surface. the snow cover was 0.20 m thick with an average density of 200 kg m−3 and crystal sizes of 0.5 to 1 mm. The peak pressures measured at all of the microphones were markedly reduced compared to pressures measured when a snow cover was not present because of the well‐known absorptive effect of the snow. In addition, waveforms near the surface displayed a strong, low‐frequency ‘‘tail’’ following the impulsive arrival from the shot. This tail was found to decay exponentially with height z above the surface [∼e−αz], a diagnostic feature of su...

The propagation paths from shallow explosive sources to a SOFAR axial receiver located near Midway Island were determined by examination of the arrival pattern making up each received shot signature. The sources were detonated at shallow depths (200 m) along a 1650 km track NE of the hydrophone. Shot signatures were aligned by computer on the basis of travel time and range. The identification of arrivals was based upon a comparison of this signature alignment with one produced by computed signatures using TRIMAIN, a mathematical ray trace model. The principal ray paths are RR, deep cycling rays which can be classified by the number of times they have turned under below the SOFAR axis. Large scale oceanographic features determine the arrival structure and serve to identify the ray paths producing it.

Explosive acoustic sources were dropped from a ship traversing a course approximately perpendicular to a line from the ship to a hydrophone of the Pacific Missile Impact Locating System (P‐MILS) near Midway Island. The rectified shot signatures recorded from the hydrophone were aligned for identification of arrivals and assignment to ray paths. The alignment revealed that some arrivals predicted by ray‐trace calculations were missing from some signatures. The signals traveled across an area of seamounts located north of the Hawaiian Ridge and the missing arrivals are related to ray‐path blocking. The blocked ray paths, and the specific seamounts responsible for the blockages, are identified for three selected shot signatures. The shadowing of the hydrophone by identifiable seamounts for CW signals from a towed, 14.65‐Hz source is correlated with the blockage of propagation paths for the shot signals.

Shots of 1000, 2000, and 3000 lb of TNT, detonated on the bottom of the 150‐f (fathom) Northeast Trough of the Gulf of Maine, were monitored at deep hydrophone locations on the continental slope off the United States of America, Bermuda, and the Antilles. Four types of arrivals were received from these shots: (1) ground arrivals, which were received at distances up to 250 miles from the shot; (2) direct arrivals that traveled along great circle, all‐water paths to receivers up to 1800 miles away; (3) indirect arrivals that traveled down the Northeast Trough and thence to the receivers; and (4) reflections from seamounts that lie off the mouth of the Northeast Trough.

Shots were fired at a fixed location and constant shallow depth at 12‐hr intervals over a period of 15 hr. Shots fired in this way produced a highly repeatable signal. The signals were received at a fixed location 63 miles away on hydrophones at 3000‐ and 9100‐ft depths. The signals exhibit about 40% correlation over a period of 12 hr and about 20% correlation over a period of 1 hr.

Apparatus for generating seismic waves including an upstanding hollow cylindrical housing within which an impact piston latched in a cocked position is adapted to be propelled downwardly by high pressure expanding gas in the confined chamber above it within the housing so as to strike a target plate resting on the ground adjacent the lower end of the housing. After each blow against the target, the piston is retracted upwardly by means of hydraulic cylinders which recompress the gas in the chamber to its original pressure. Since there is no need for recharging the pressure chamber after each shot, economical rapid cycle operation is facilitated.

A detailed seismic survey is achieved when there is general knowledge of a formation with generally steep dip by first locating the central location point and then mapping radial shot lines and receiver lines therefrom. The shot lines need to extend across the dip and beyond. The receiver lines need to extend a normal distance as with conventional 3-D seismic surveys. Shots from the central location progressing outwardly will reflect first with equal incident and reflector paths, then with a short incident to long reflector path, and finally to where long incident and short reflector paths are achieved. The data collected radially to describe the formation is near one-tenth of that required for conventional 3-D surveys where the shot lines and the receiver lines are mapped in parallel survey lines.

A gun shot control unit for a seismic exploration system compensates for the inherent delay between the shot command signal and the actual occurrence of the seismic pulse. A digital clock is synchronized with an external source. Timing pulses occurring at a time preceding the timing pulse upon which the occurrence of a seismic pulse is desired are produced by the clock. These timing pulses start a digital counter at a time preceding the desired time of occurrence of the seismic pulse. This counter is adjustable so that the delay which interposes between the timing and the actual occurrence of the seismic pulse can be minimized.

An improved seismic prospecting system comprising the use of a closely spaced sequence of source initiations at essentially the same location to provide shorter objective-level wavelets than are obtainable with a single pulse. In a preferred form, three dynamite charges are detonated in the same or three closely spaced shot holes to generate a downward traveling wavelet having increased high frequency content and reduced content at a peak frequency determined by initial testing.

The Naval Research and Development Activity (NORDA) recently conducted a very low‐frequency (VLF) acoustic experiment in a sloping bottom environment off the coast of Oregon. A 16‐element vertical hydrophone array was deployed in water depths of 200 and 400 m. An upslope and two cross slope explosive shot lines were completed. In addition, an upslope cw (15 Hz) tow was recorded. This paper uses the results of this experiment to investigate the importance of bottom shear and bathymetric variation on energy partitioning between water and ground paths. The measured data are compared with predictions from SAFARI, a range‐independent model that allows conversion to shear energy in the bottom, and PE, an acoustic model that allows variable bathymetry. Two different PE codes are used, viz., IFDPE and a PE pulse code recently developed at NORDA (M. Collins), which allows for subbottom structure that is not necessarily parallel to the ocean bottom. Measured cw propagation loss and explosive shot record sections are compared with predicted results from both SAFARI and PE.

A method of seismic prospecting with very high resolution as applicable in particular to exploitation of a productive hydrocarbon deposit essentially consists in transmitting and receiving acoustic waves, in recording shot moments, in determining average propagation velocities of refracted and reflected waves and in establishing a depth-section in order to determine the positions of interfaces located within the geological zone traversed horizontally by a horizontal borehole.

The propagation paths from shallow explosive sources to a SOFAR axial receiver are determined by analyzing measured shot signatures. The charges were detonated along a 2800‐km track between Antigua and Newfoundland. Propagation was through several distinct water masses, each of which produced different observable effects on the shot signature. Because of the shallow depth of the source, the number of turning points below the SOFAR axis is the prime determinant of the time dispersion of the arrivals and is a convenient basis for classifying them. The range dependence of the dispersed arrivals depends on the large‐scale oceanography and discloses the identity of the ray paths which produce it.Subject Classification: [43]30.20.

Impact driven tools of the type generally comprising a bitter end bounded by a collar and a shank and a tip are provided with internal silencing means comprising an opening in the bitter end, said opening filled with a sound attenuating material, which is preferably steel shot loosely packed in the opening and retained therein by a force fit plug secured by a weld. The opening is preferably axial and extends through the bitter end to or below the collar. In large diameter impact driven tools multiple openings are provided parallel to the axis and terminating at staggered points. Each such hole is filled with a sound attenuating material, such as steel shot. The rams of impacting apparatus, or air hammers, are also provided with internal silencing means comprising at least one opening, each such opening being filled with sound attenuating material, which is preferably steel shot loosely packed and retained by a force fit plug secured by a weld.

Sound waves propagated through the sea floor from explosions near the sea's surface have yielded much knowledge of the velocity structure of the oceanic crust. The interpretation of the observations is customarily based on the relation between the wave travel time and the distance between shot and receiver. The records of received sound are usually used merely for identification and measurement of the time of the first arrivals of significant waves. It is also of interest to consider the problem in terms of the intensity and spectrum of the entire train of waves propagated through the sea floor. The sea observations have the advantage of a uniformity and elastic simplicity of the medium at the source and receiver not possessed by similar observations on land. (This paper represents results of research carried out by the University of California under contract with the U. S. Navy Department.)

Several salvos of nine explosive sources were lowered from a drifting ship to a depth of 2000 ft in water 14 500 ft deep, and the sources were fired seriatim at 1‐min intervals by electrical detonation. Thus, all sources of a given salvo were fired approximately at the same point in the ocean. The arrivals at the hydrophone, suspended at 1000 ft below the surface from an anchored ship, were recorded in eight half‐octave frequency bands between center frequencies of 63 and 720 cps, along with timing‐signals and radio‐transmitted shot instants by use of two six‐channel photographically recording oscillographs. The degree of uniformity of the arrivals from the shots of each salvo is shown, and some observed effects of reflection from ocean bottom and surface are discussed. (This work was supported by the Office of Naval Research.)

Under certain highly simplified but realistic physical assumptions, the basic data from continuous velocity surveys in wells can be made to simulate the variations in acoustic impedance in the ground which give rise to seismic reflections. An electro‐optical analog device is described which makes use of the basic well data to produce synthetic seismic records which resemble actual seismograms from shot hole explosions. This provides an interesting insight into the requisite physical conditions as well as the physical processes whereby seismic reflections are set up in the earth.

The following experiment was performed on the beach at Fire Island in an area whose geophysical structure is well known: vertical component geophones were planted in the sand near the surf, and recordings were made of particle velocities in the surface sand layer. At the same time motion pictures were taken of the breaking water waves. The pattern of signal bursts and relative silences found in these surfsesims correlates well with surf behavior. Spectrum analyses of surfseisms have been obtained over a frequency range from 10 to 50 cps. An analysis of the dispersive wave train produced by a simulated shot source shows very low group velocities of the order of several hundred ft/sec. A qualitative theory of surfseism phenomena will be presented. (This work was supported by the Office of Naval Research.)

The sound of a gunshot in a studio is difficult to reproduce. In the home it often sounds more like the snap of a finger than the roar of a gun. The factors responsible are described, together with a means of circumventing their combined effect. A shot may be electronically reinforced with great realism through the use of simulated reverberation. This is keyed on automatically by the initial impact and then decayed gradually to create the effect of a longer shot, which in turn produces a louder sound. Methods are also described for generating several special effects, such as the distant roar of cannon fire, the chatter of machine guns, and the ricochet whine of bullets.

The 3×2.5 square‐meter glass plate was driven electrodynamically at the center and the amplitude distribution as a function of the frequency was recorded for positions out to and along the edge of the plate. The loss factor was measured by both bandwidth and decay methods. Transients were excited by a shot from a blank pistol and photographs of the resulting oscilloscope pattern were taken. (This work was sponsored by the U. S. Atomic Energy Commission and Bureau of Naval Weapons.)

An explosive noise source which uses a 10‐ga blank shotgun shell has been used for measuring the acoustical performance of sound attenuating passages such as those used in jet engine test facilities and large ventilation systems. The source has a peak power output of the order of 10 000 watts, is portable, and has a high degree of repeatability. The frequency spectrum on an octave band basis closely simulates that of a typical jet engine. Instrumentation has been developed for analyzing the results of shot tests and close agreement between these and pure tone and random noise test techniques has been obtained.

The return by the deep‐ocean bottom of the sound of an explosive charge consists of an initial burst followed by a long tail representing back‐scattered sound at decreasing grazing angles with the bottom. Through analysis of shot records at a number of deep‐water locations in the North Atlantic, the back‐scattering coefficient of the bottom has been obtained as a function of grazing angle between 30° and 90°. The results indicate that the deep‐sea bed behaves as a diffuse or Lambert‐law back scatterer at grazing angles from 30° to about 65°; between 65° and 90° (normal incidence), the coefficient rapidly increases, as though specular reflection from normally oriented flat facets of the bottom were occurring. This behavior with angle is similar to that of the sea surface. Analyses in several frequency bands in the range 0.5 to 8.0 kc suggest that the back‐scattering coefficient decreases with frequency at a rate of about 2 db per octave.