In an effort to provide guidelines for law enforcement personnel to protect their hearing, the peak pressure level and signal duration (A and B duration) of eight popular firearms were measured and compared with the requirements of OSHA (1970), CHABA DRC (1968), and EPA levels (1974). Small condenser microphones and a storage oscilloscope were used to record the blast wave signatures from a 9-mm automatic, 0.357-cal. Magnum revolver, 0.41-cal. Magnum revolver, 0.22-cal. revolver, 0.45-cal. automatic, 0.44-cal. Magnum revolver, 12-gauge shotgun, and 0.22-cal. rifle. Measurements were made at the ear of the person shooting and at the approximate position of a neighbor at a firing range. Some measurements were also made at a practice firing range. A portable tape recorder was found useful for recording gun signals and measuring B durations. The peak pressure levels of the signatures of all the firearms tested exceed the OSHA maximum of 140 dB. It was found that in an anechoic environment the noise from five of the handguns exceeded the CHABA DRC (1968), while the noise from all of the firearms tested, except the 0.22-cal. rifle, exceeded the EPA levels (1974). At a sound-insulated firing range, the noise from all the firearms tested, except the 0.22-cal. rifle, exceeded the CHABA DRC (1968), while all the firearms tested exceeded the EPA levels (1974).
A study has been made of the influence of transient and intermodulation distortion on the transmission of speech occurring in the presence of a background noise having pronounced transient characteristics (cafeteria noise). This paper describes objective measurements of the power-time distribution in speech and noise, separately and in combination, for the sound coming from a sound source of high quality and for the sound coming from the earphones of hearing aids whose microphones were exposed to the sound source. The nature of the transmitted signal will be demonstrated. (This work was carried out under sponsorship of Veterans Administration.)
Small condenser microphones and a storage oscilloscope were used to record the N-wave signatures from a 9-mm Ruger, 0.357 magnum, 0.41 magnum, 0.22 long rifle, 0.44 magnum, 12-gauge shotgun, and 0.22 rifle. Measurements were made at the ear of the person shooting and at the approximate position of a neighbor at a firing range. Data on peak SPL and durations (A and B durations) are given, as well as data obtained at a practice firing range. The results are discussed from the point of view of using ear defenders to protect against temporary and permanent threshold shift incurred during practice. [Research supported by the National Institute of Law Enforcement and Criminal Justice.]
The attenuation provided by seven different circumaural hearing protectors on the newly-standarized aluminum artifical head was measured for parallel and perpendicular sound incidence. The impulse sound source was a 38-caliber handgun shooting blanks, which created a 150-dB re 20 μPa peak sound pressure level with an A-duration of 0.13 ms. The ear protector was 1 m from the gun. The incident noise impulse external to the ear protector was measured with a “1/8-in.” condenser microphone and the resultant noise inside the ear protector was measured with a “1/4-in.” condenser microphone. These two impulse signals were captured in a digital transient storage device from which both a pressure amplitude versus time plot and a magnetic tape recording were made. The tape recording was used to obtain a spectral analysis employing a time-compression real-time analyzer. The attenuation of the peak levels and the energy-density spectrum of the ear protector was found by suitable comparison of the external and internal signals. The energy density results show that most of the energy of the noise inside the ear protectors is at low frequencies.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.