Gunshot Sounds Research Articles

Dissecting recorded gunshot sounds

Gunshot audio recordings are composites of multiple sound sources, including blast, ballistic, mechanical, and environmental sounds. The existence of each sound and its distinguishing features depend on the source characteristics, the propagation environment, and the recording system. Controlled recordings show the situational dependence of these sound sources and the recording system. Knowledge of the physics and these dependences is critical in forensic analysis and the ability to dissect, separate, and identify sources in recorded gunshots. Multiple blast sources (muzzle blast, gas jet, mechanical impact, and primer explosion), ballistic sources (shockwave and subsonic flow), and environmental sources (reflections and terminal impact) will be shown from both controlled experiments and uncontrolled forensic recordings.

Measurements, Analysis, Classification, and Detection of Gunshot and Gunshot-like Sounds

Gun violence has been on the rise in recent years. To help curb the downward spiral of this negative influence in communities, machine learning strategies on gunshot detection can be developed and deployed. After outlining the procedure by which a typical type of gunshot-like sounds were measured, this paper focuses on the analysis of feature importance pertaining to gunshot and gunshot-like sounds. The random forest mean decrease in impurity and the SHapley Additive exPlanations feature importance analysis were employed for this task. From the feature importance analysis, feature reduction was then carried out. Via the Mel-frequency cepstral coefficients feature extraction process on 1-sec audio clips, these extracted features were then reduced to a more manageable quantity using the above-mentioned feature reduction processes. These reduced features were sent to a random forest classifier. The SHapley Additive exPlanations feature importance output was compared to that of the mean decrease in impurity feature importance. The results show what Mel-frequency cepstral coefficients features are important in discriminating gunshot sounds and various gunshot-like sounds. Together with the feature importance/reduction processes, the recent uniform manifold approximation and projection method was used to compare the closeness of various gunshot-like sounds to gunshot sounds in the feature space. Finally, the approach presented in this paper provides people with a viable means to make gunshot sounds more discernible from other sounds.

Tanah Adalah “Rahim” Perempuan Papua

Papua experiences turmoil almost every year and often becomes an interesting subject for public discourse. However, Papuans are powerless when it comes to determining their own future. For sixty years (1962-2022), Papuans have to survive amidst the smell of bloodshed and the sounds of gunshots, demonstrations, lamentations, and other commotions that hinder human development. These have invited various parties to gather and think for solutions for peace. Despite this, the ideology of “NKRI Harga Mati” (Non-negotiable Sovereignty of the Unitary State of the Republic of Indonesia) has gained more popularity than the humane concept of Pancasila. The conflict driven by populist ideology has created scars in the history of the indigenous people of Papua, especially for Papuan women. The 117 years (1905-2022) of the Gospel preached in Papua has not been sufficient to liberate the Papuans. The patriarchy that preaches justice and humanity is likened to a fashion show for false generosity. They cry out for justice and yet they oppress Papuan women. This experience calls for a theological reflection from the lives of Papuan women. In using Delores S. William’s womanist theological framework, the author will discover how God speaks in the history of Papuan women and how God acts through their being.

Data Collection, Modeling, and Classification for Gunshot and Gunshot-like Audio Events: A Case Study.

Distinguishing between a dangerous audio event like a gun firing and other non-life-threatening events, such as a plastic bag bursting, can mean the difference between life and death and, therefore, the necessary and unnecessary deployment of public safety personnel. Sounds generated by plastic bag explosions are often confused with real gunshot sounds, by either humans or computer algorithms. As a case study, the research reported in this paper offers insight into sounds of plastic bag explosions and gunshots. An experimental study in this research reveals that a deep learning-based classification model trained with a popular urban sound dataset containing gunshot sounds cannot distinguish plastic bag pop sounds from gunshot sounds. This study further shows that the same deep learning model, if trained with a dataset containing plastic pop sounds, can effectively detect the non-life-threatening sounds. For this purpose, first, a collection of plastic bag-popping sounds was recorded in different environments with varying parameters, such as plastic bag size and distance from the recording microphones. The audio clips’ duration ranged from 400 ms to 600 ms. This collection of data was then used, together with a gunshot sound dataset, to train a classification model based on a convolutional neural network (CNN) to differentiate life-threatening gunshot events from non-life-threatening plastic bag explosion events. A comparison between two feature extraction methods, the Mel-frequency cepstral coefficients (MFCC) and Mel-spectrograms, was also done. Experimental studies conducted in this research show that once the plastic bag pop sounds are injected into model training, the CNN classification model performs well in distinguishing actual gunshot sounds from plastic bag sounds.

Advocacy, Social Justice, and Counselor Identity During the Black Lives Matter Movement

Advocacy, Social Justice, and Counselor Identity During the Black Lives Matter Movement

Song production by the North Pacific right whale, Eubalaena japonica.

This paper describes song production by the eastern North Pacific right whale (NPRW, Eubalaena japonica) in the southeastern Bering Sea. Songs were localized in real-time to individuals using sonobuoys. Singers whose sex could be determined were all males. Autonomous recorder data from 17 year-long deployments were analyzed to document and characterize song types. Four distinct song types were documented over eight years (2009-2017) at five distinct locations. Each song type consists of a hierarchical structure of 1-3 different repeating phrases comprised predominantly of gunshot sounds; three of the four songs contained additional sound types (downsweep, moan, and low-frequency pulsive call). Songs were detected annually (July-January); all song types remained consistent over eight years. Two different songs often occurred simultaneously, produced by different individuals; the same song was never detected simultaneously at the same location. The same song type was detected on the same day and time at two distant locations, indicating multiple individuals can produce the same song. These findings provide support that males produce song; it remains unknown if females also sing. NPRW is the first right whale species documented to produce song. Based on current knowledge about song in mysticetes, it is hypothesized that these songs are reproductive displays.

The near repeats of gun violence using acoustic triangulation data

Near repeat signatures of gun violence have been generated exclusively from incidents reported to or discovered by police. However, many gun crimes go unreported. In Trenton NJ, it is believed as many as 60% of all such cases do not come to the police’s attention. This research explores near repeat qualities of gun-related violent crime in Trenton using an underutilized dataset, sounds of gunshots from ShotSpotter, allowing us to capture both reported and unreported gun-related violent crime. When examining reported and unreported gun violence, compared to solely relying on reported cases, near repeat signatures are smaller geographically and exhibit larger and more consistent statistically significant effects across temporal bands. Near repeat chains also occur more frequently and include more events. We caution against only using reported events in near repeat analyses. Improved measures of crime may change the character of near repeat events, research findings, and the operational response.

Estimating North Pacific Right Whale calling depths in the Bering Sea via modal dispersion

Calling depth distributions and ranges are estimated for two types of calls produced by critically endangered eastern North Pacific right whales (NPRW) in the Bering Sea, using passive acoustic data collected with bottom-mounted single-hydrophone recorders at the 50 m isobath. Nonlinear time resampling of 12 NPRW “upcalls” and 20 broadband “gunshots” typically isolated 3 to 4 individual mode arrivals below 200 Hz. Matched-mode processing (MMP) methods were then used to estimate range, depth, and propagation environment. When plotted as a function of range and frequency, MMP ambiguity surfaces reveal the existence of large sound speed gradients in the sediment, along with strongly downward-refracting sound speed profiles during certain summer/fall seasons. Refractive propagation effects from these profiles can induce dramatic changes in signal structure that required new developments in “warping” techniques. Gunshot sounds were generally produced at a few meters depth, while upcall depths clustered between 10 and 25 m, consistent with previously published bioacoustic tagging results from North Atlantic right whales. Current work is examining whether consistent differences exist in the calling depths of bowhead, humpback, and right whales, which could potentially provide a feature for species classification of ambiguous calls. [Work sponsored by NPRB.]

A low power mixed signal correlator for power efficient sound signature detection and template matching

PurposeSensor networks have found wide applications in the monitoring of environmental events such as temperature, earthquakes, fire and pollution. A major challenge with sensor network hardware is their limited available energy resource, which makes the low power design of these sensors important. This paper aims to present a low power sensor which can detect sound waveform signatures.Design/methodology/approachA novel mixed signal hardware is presented to correlate the received sound signal with a specific sound signal template. The architecture uses pulse width modulation and a single bit digital delay line to propagate the input signal over time and analog current multiplier units to perform template matching with low power usage.FindingsThe proposed method is evaluated for a chainsaw signature detection application in forest environments, under different supply voltage values, input signal quantization levels and also different template sample points. It is observed that an appropriate combination of these parameters can optimize the power and accuracy of the presented method.Originality/valueThe proposed mixed signal architecture allows voltage and power reduction compared with conventional methods. A network of these sensors can be used to detect sound signatures in energy limited environments. Such applications can be found in the detection of chainsaw and gunshot sounds in forests to prevent illegal logging and hunting activities.

Using nonlinear time warping to estimate North Pacific right whale calling depths in the Bering Sea.

Calling depth distributions are estimated for two types of calls produced by critically endangered eastern North Pacific right whales (NPRWs) in the Bering Sea, using passive acoustic data collected with bottom-mounted hydrophone recorders. Nonlinear time resampling of 12 NPRW "upcalls" and 20 "gunshots" recorded in a critical NPRW habitat isolated individual normal mode arrivals from each call. The relative modal arrival times permitted range estimates between 1 and 40 km, while the relative modal amplitudes permitted call depth estimates, provided that environmental inversions were obtained from high signal-to-noise ratio calls. Gunshot sounds were generally only produced at a few meters depth, while upcall depths clustered between 10 and 25 m, consistent with previously published bioacoustic tagging results from North Atlantic right whales. A Wilcoxon rank sum test rejected the null hypothesis that the mean calling depths of the two call types were the same (p = 2.9 × 10-5); the null hypothesis was still rejected if the sample set was restricted to one call per acoustic encounter (p = 0.02). Propagation modeling demonstrates that deeper depths enhance acoustic propagation and that source depth estimates impact both NPRW upcall source level and detection range estimates.

Vocal behavior and ontogeny of Northern right whales in the southeast critical habitat

North Atlantic right whales are one of the most endangered of the great whales. A remnant population of ~500 inhabits the eastern seaboard of North America. A small fraction (2%) travels south to their critical calving habitat along the Florida and Georgia coast. By late November and through the winter, right whales give birth and nurse their calves in these shallow waters before departing in early spring to their northern habitats. In the southeast critical habitat mother-calf pairs remain generally isolated from other whales, presenting a unique platform to study vocal development and learning in large whales. Using small boats, GPS-instrumented, free-drifting autonomous acoustic buoys were deployed in close proximity to 44 photo-identified mother-calf pairs over 7 calving seasons. Surface video and synchronized underwater recordings documented their social and vocal behavior. With the exception of some low-energy gunshot sounds, mothers, and their calves, remained predominantly silent during the first 4 weeks. This might be due to calf maturation, and or a strategy to avoid harassment by other whales or potential predators. Over 100 calls have been analyzed from 15 different calves. Some of these calves were resampled at different stages at <1 week up to 12 weeks of age. Evidence of individual and age-related variance and changes in call structure, complexity, power, rates, as well as vocal mimicry are presented. [Funding: HBOI Florida PFW License Plate Fund, The Harry Richter Foundation and IBM, NOAA Permit #14233.]

Baby's first words: Vocal behavior and ontogeny of Northern right whales in the southeast critical habitat

North Atlantic right whales are one of the most endangered of the great whales. A remnant population of ~500 inhabits the eastern seaboard of North America. A small fraction (2%) travels south to their critical calving habitat along the Florida and Georgia coast. By late November and through the winter, right whales give birth and nurse their calves in these shallow waters before departing in early spring to their northern habitats. In the southeast critical habitat mother-calf pairs remain generally isolated from other whales, presenting a unique platform to study vocal development and learning in large whales. Using small boats, GPS-instrumented, free-drifting autonomous acoustic buoys were deployed in close proximity to 44 photo-identified mother-calf pairs over 7 calving seasons. Surface video and synchronized underwater recordings documented their social and vocal behavior. With the exception of some low-energy gunshot sounds, mothers, and their calves, remained predominantly silent during the first ...

Using passive acoustics to investigate seasonal and diel trends in acoustic behavior of North Atlantic right whales (Eubalaena glacialis)

The North Atlantic right whale (Eubalaena glacialis), an endangered baleen whale species, produces a variety of stereotyped acoustic signals. One signal, the “gunshot” sound, has only been recorded from adult males and is thought to function for reproduction, either as advertisement for females or an agonistic signal toward other males. This study uses remote acoustic monitoring to analyze the presence of gunshots over a two-year period at two sites on the Scotian Shelf to determine if there is evidence that right whales use these locations for breeding activities. Seasonal analyses at both locations indicate that gunshot production is highly seasonal, with an increase in autumn. One site had significantly more gunshot sounds and exhibited a clear diel trend in signal production. The other site also showed a seasonal increase during autumn, but did not show any significant diel trends. This site difference indicates variation either in the number or the behavior of whales at each location. The timing of the observed seasonality in gunshot production is consistent with the current understanding of right whale breeding season, and these results demonstrate that detection of gunshots with remote acoustic monitoring can be a reliable way to track seasonal mating activities.

Female North Atlantic right whales produce gunshot sounds

North Atlantic right whales (Eubalaena glacialis) produce loud, broadband, short duration sounds referred to as gunshots. The sounds have been hypothesized to function in a reproductive context, as sexual advertisement signals produced by solitary adult males to attract females and/or agonistic displays among males in surface active groups. This study provides evidence that gunshot sounds are also produced by adult females and examines the acoustics and behavioral contexts associated with these calls. Results from boat-based observational surveys investigating the early vocal ontogeny and behavior of right whales in the critical southeast calving habitat are presented for a subset of mothers who produced gunshots while in close proximity to their calves. Of 26 different isolated mother-calf pairs, gunshots were recorded from females of varied ages and maternal experience. The signals were recorded when calves separated from their mothers during curious approaches toward objects on the surface. While the spectral and temporal characteristics of female gunshots resemble those attributed to adult males, these calls were orders of magnitude quieter (Ő30 dB). Relatively quiet gunshots posed minimal risk of injury to nearby calves. The social and behavioral context suggests gunshots were associated with maternal communication and may also be indicators of stress and agitation.

Remote Acoustic Monitoring of North Atlantic Right Whales (Eubalaena glacialis) Reveals Seasonal and Diel Variations in Acoustic Behavior

Remote acoustic monitoring is a non-invasive tool that can be used to study the distribution, behavior, and habitat use of sound-producing species. The North Atlantic right whale (Eubalaena glacialis) is an endangered baleen whale species that produces a variety of stereotyped acoustic signals. One of these signals, the “gunshot” sound, has only been recorded from adult male North Atlantic right whales and is thought to function for reproduction, either as reproductive advertisement for females or as an agonistic signal toward other males. This study uses remote acoustic monitoring to analyze the presence of gunshots over a two-year period at two sites on the Scotian Shelf to determine if there is evidence that North Atlantic right whales may use these locations for breeding activities. Seasonal analyses at both locations indicate that gunshot sound production is highly seasonal, with an increase in the autumn. One site, Roseway West, had significantly more gunshot sounds overall and exhibited a clear diel trend in production of these signals at night. The other site, Emerald South, also showed a seasonal increase in gunshot production during the autumn, but did not show any significant diel trend. This difference in gunshot signal production at the two sites indicates variation either in the number or the behavior of whales at each location. The timing of the observed seasonal increase in gunshot sound production is consistent with the current understanding of the right whale breeding season, and our results demonstrate that detection of gunshots with remote acoustic monitoring can be a reliable way to track shifts in distribution and changes in acoustic behavior including possible mating activities.

Characteristics of gunshot sound displays by North Atlantic right whales in the Bay of Fundy

North Atlantic right whales (Eubalaena glacialis) produce a loud, broadband signal referred to as the gunshot sound. These distinctive sounds may be suitable for passive acoustic monitoring and detection of right whales; however, little is known about the prevalence of these sounds in important right whale habitats, such as the Bay of Fundy. This study investigates the timing and distribution of gunshot sound production on the summer feeding grounds using an array of five marine acoustic recording units deployed in the Bay of Fundy, Canada in mid-summer 2004 and 2005. Gunshot sounds were common, detected on 37 of 38 recording days. Stereotyped gunshot bouts averaged 1.5 h, with some bouts exceeding 7 h in duration with up to seven individuals producing gunshots at any one time. Bouts were more commonly detected in the late afternoon and evening than during the morning hours. Locations of gunshots in bouts indicated that whales producing the sounds were either stationary or showed directional travel, suggesting gunshots have different communication functions depending on behavioral context. These results indicate that gunshots are a common right whale sound produced during the summer months and are an important component in the acoustic communication system of this endangered species.

Sound production behavior of individual North Atlantic right whales: implications for passive acoustic monitoring

Passive acoustic monitoring is being used to detect vocalizing marine mammals. Data on call types and individual rates of sound production are necessary to use passive acoustics to identify species, assess individual detectability, and estimate the number of individuals present. The present study describes the sound production behavior of endangered North Atlantic right whales Eubalaena glacialis in the Bay of Fundy, Canada, during July and August, recorded with suction cup archival tags (Dtag) in 2000 to 2002 and 2005. The Dtag simultaneously recorded acoustic data from a hydrophone along with the depth and orientation of the whale. Over 168 h of acoustic data were obtained from 46 tag deployments (35 ind.), with an average attachment dura- tion of 4.5 h. The rate of sound production was variable, ranging from 0 to 200 calls h �1 (mean ± SD: 6.4 ± 29.8 calls h �1 ), with 28 of the 46 tagged whales producing no calls (corresponding to 69/168 h of data). Right whale sounds from any whale in the area were recorded on most tag records, indicating that aggregations of whales may be detected more reliably than individuals. Calling rates were highest during surface activity and traveling and lowest during foraging and logging behavior. Whales of both sexes and all age-classes produced upcalls and other tonal calls, and 1 adult male produced gunshot sounds. The present study provides insight from the largest extant collection of recordings of individual North Atlantic right whales into the acoustic detectability of individual right whales and demonstrates that the behavioral state is the primary factor affecting calling rate.

An introduction to forensic gunshot acoustics

Due to the proliferation of audio recording devices in the military, law enforcement, and the civilian community, there has been an increase in the number of recorded gunshot sounds submitted for forensic analysis. A gunshot sound is composed of one or more discrete acoustic transient events. The two primary acoustic events are the muzzle blast (bang) and the ballistic shockwave (crack). The acoustic event characteristics depend on their source generating mechanisms and vary according to the firearm make, model, barrel length, and the specific ammunition characteristics. Forensic gunshot analysis deals with a single recorded shot lasting for a fraction of a second. These acoustic events are usually high intensity, often up to 160 dB SPL, are highly directional, and are often recorded in high distortion environments. Forensic gunshot analysis must take into account variations in the source generation characteristics and the sources of distortion for these recorded acoustic events in order to answer these fundamental forensic questions: Is this event a gunshot? Are two events from the same firearm? Who fired first? To illustrate the complex nature of the analysis, we present the gunshot data collected in a pristine controlled environment and the data collected in a forensic environment.

Spatial distribution of right whale “gunshot” sound displays in the Bay of Fundy, Canada.

North Atlantic right whales (Eubalaena glacialis) produce a distinctive loud broadband signal referred to as the “gunshot” sound. Current hypotheses for the function of this signal include an agonistic threat signal between males, a male reproductive advertisement signal to female right whales, or a combination of both. This sound has been documented both in a social context in mixed sex surface active groups and by lone individual males in a stereotyped display. An array of five archival bottom mounted acoustic recorders was deployed in the Center of the North Atlantic Right Whale Conservation Area in the Bay of Fundy, Canada in August 2005. The five recorders were spaced 3–7 nm apart, allowing for localization of whales producing gunshot sounds within or near the array. These recordings were used to describe the regional distribution, spacing, movement patterns, and timing of gunshot sound displays produced by right whales over a two week period to investigate the potential function of this sound. Further investigations included both the diel trends in the sound production and evidence for interactions between individuals simultaneously producing these displays.

Synchronization of the acoustic evidence in the assassination of President Kennedy

We have revisited the acoustic evidence in the Kennedy assassination--recordings of the two Dallas police radio channels upon which our original NRC report (Ramsey NF et al., Report of the Committee on Ballistic Acoustics. National Research Council (US). Washington: National Academy Press, 1982. Posted at http://www.nap.edu/catalog/10264.html) was based--in response to the assertion by DB Thomas (Echo correlation analysis and the acoustic evidence in the Kennedy assassination revisited. Science and Justice 2001; 41: 21-32) that alleged gunshot sounds (on Channel 1), apparently recorded from a motorcycle officer's stuck-open microphone, occur at the exact time of the assassination (as established by emergency communications on Channel 2). We have critically reviewed these two publications, and have performed additional analyses. In particular we have used recorded 60 Hz hum and correlation methods to obtain accurate speed calibrations for recordings made on both channels, cepstral analysis to seek instances of repeated segments during playback of Channel 2 (which could result from groove jumping), and spectrographic and correlation methods to analyze instances of putative crosstalk used to synchronize the two channels. This paper identifies serious errors in the Thomas paper and corrects errors in the NRC report. We reaffirm the earlier conclusion of the NRC report that the alleged "shot" sounds were recorded approximately one minute after the assassination.