SSS.6.9 - Research Supplement: MOD9 FS, Obsidian 45, and Trident-9 Further Analysis
/CGS MOD9 FS, Rugged Obsidian 45, and SWR Trident-9 on the HK P30L Full-Size 9mm Semiautomatic Pistol
The previous Sound Signature Reviews of the CGS MOD9 FS (6.6), Rugged Obsidian 45 (6.7), and SWR Trident-9 (6.8) presented typical sound signatures of the silencers on a full-size 9mm semiautomatic combat handgun. In PEW Science testing, the MOD9 FS achieved a Suppression Rating of 55.4. The Obsidian 45 achieved a rating of 53.7 in its long configuration. The Trident-9 achieved a rating of 53.2.
This members-only research supplement is intended to provide more information to PEW Science members with regard to specific sound signature characteristics of the tested configurations in the aforementioned reviews and to help frame objective loudness comparisons between the three silencers. This supplement is part of ongoing PEW Science small arm weapon system sound signature research.
Below, summaries are presented for a three-way comparison of first round pop (FRP) and 5-shot average sound performance. Detailed data and analysis follows.
Overall Summary: The Trident-9 exhibits the superior FRP performance of the three silencers, at both the muzzle and ear. The MOD9 FS exhibits the superior average muzzle performance (which correlates to bystander perception). The Obsidian 45 exhibits the superior average ear performance (which correlates to shooter perception). The MOD9 earns the highest suppression rating on the weapon system due to its combination of overall muzzle and ear performance. The SWR Trident-9 seems to exhibit a “higher pitched” sound signature as shown in analytical human inner ear modeling and as perceived anecdotally by shooters and bystanders.
FRP Summary: When paired with the HK P30L full-size 9mm semiautomatic combat handgun, the CGS MOD9 FS may have an FRP approximately 25% less intense than that of the Rugged Obsidian 45 in its long configuration, 1.0 m left of the weapon muzzle. The FRP of the SWR Trident-9 may be approximately 59% less intense than that of the Obsidian 45.
At the shooter’s ear, the Obsidian 45 may have an FRP approximately 59% less intense than that of the MOD9 FS. The FRP of the SWR Trident-9 may be approximately 64% less intense than that of the MOD9 FS.
5-Shot Average Summary: When considering a 5-shot average, the Obsidian 45 may have a sound signature approximately 1% less intense than that of the Trident-9, 1.0 m left of the weapon muzzle. The sound signature of the MOD9 FS may be approximately 16% less intense than that of the Trident-9.
At the shooter’s ear, when considering a 5-shot average, the MOD9 FS may have a sound signature approximately 5% less intense than that of the Trident-9. The sound signature of the Obsidian 45 may be approximately 33% less intense than that of the Trident-9.
6.9.1 Comparisons of Muzzle Waveforms Measured in the Free Field
It is not always possible to determine relative, objective loudness from only the measured average peak sound pressure amplitude and measured peak sound pressure momentum transfer potential (impulse). Therefore, the Suppression Rating also considers physical ear response to measured sound signatures. The human inner ear responds to different sound pressure frequencies with varying sensitivity. Physically, these frequencies excite different regions of the basilar membrane within the cochlea. The human ear is typically most sensitive to sounds that excite the membrane near a frequency of 4,000 Hz. However, the ear may be exercised, and therefore damaged, at different physical regions. It is postulated that this inner ear response directly correlates to the perceived loudness of suppressed small arms.
Figure 1 presents the results of an inner ear analysis performed using measured sound overpressure waveforms from the first shots in the three previous tests presented in reviews 6.6, 6.7, and 6.8. The curves show normalized physical response of the human inner ear as a function of basilar membrane location within the cochlea and corresponding sensitivity frequencies. On the left, Fig 1a shows the response on the vertical axis with a linear scale. Fig 1b shows the same data on a logarithmic scale. Note that the data is normalized; this lets you see the relative theoretical ear response for the three silencers. To personnel located 1.0 m left of the weapon muzzle, the CGS MOD9 FS FRP signature may be approximately 25% less intense than that of the Rugged Obsidian 45 in its long configuration. The FRP of the SWR Trident-9 may be approximately 59% less intense than that of the Obsidian 45. Note the slight bias to potential higher-frequency human inner ear response of the Trident-9 between 5,000 and 6,000 Hz.
PEW Science Research Note: It is important not misconstrue the frequency-domain data in the figures with a simple frequency analysis (Fourier transform) of the time-domain overpressure waveforms presented in the reviews. The data shown in this research supplement is the output from analytical human inner ear modeling with the measured test data used as free-field overpressure loading input.
Fig 1a. Comparison of FRP Human Inner Ear Response - 9mm at the Muzzle (Linear Scale)
Fig 1b. Comparison of FRP Human Inner Ear Response - 9mm at the Muzzle (Log Scale)
Figure 2 presents the results of a second inner ear analysis performed using measured sound overpressure waveforms from the tests; this time, the curves are averages of the analysis from the five shots in each test. On the left, Fig 2a shows the response on the vertical axis with a linear scale. Fig 2b shows the same data on a logarithmic scale. Note that the data is again normalized. When considering a 5-shot average, the Obsidian 45 may have a sound signature approximately 1% less intense than that of the Trident-9, 1.0 m left of the weapon muzzle. The sound signature of the MOD9 FS may be approximately 16% less intense than that of the Trident-9.
Fig 2a. Comparison of Average Human Inner Ear Response - 9mm at the Muzzle (Linear Scale)
Fig 2b. Comparison of Average Human Inner Ear Response - 9mm at the Muzzle (Log Scale)
PEW Science Research Note: Again, note the slight bias to potential higher-frequency human inner ear response of the Trident-9 between 5,000 and 6,000 Hz. This analysis of measured test data correlates with anecdotal observations of the SWR Trident-9 being perceived as having a “higher pitched” sound signature to bystanders. This observed anecdotal correlation is the subject of continued PEW Science research interest.
6.9.2 Comparisons of Waveforms Measured near the Shooter’s Ear
The sound signatures measured at the ear during the tests of each silencer are significantly different than those measured at the weapon muzzle and this difference is not only shown in the average peak sound pressure and impulse measurements, but also with inner ear analysis.
Figure 3 presents an inner ear analysis performed using measured sound overpressure waveforms at the shooter’s right ear from the first shots in the three tests. On the left, Fig 3a shows the response on a linear vertical scale. Fig 3b shows the same data on a logarithmic vertical scale. To personnel firing the weapon, the Obsidian 45 may have an FRP approximately 59% less intense than that of the MOD9 FS. The FRP of the SWR Trident-9 may be approximately 64% less intense than that of the MOD9 FS. As was noted at the muzzle, again note the slight bias to potential higher-frequency human inner ear response of the Trident-9 above 4,000 Hz.
Fig 3a. Comparison of FRP Human Inner Ear Response - 9mm at the Ear (Linear Scale)
Fig 3b. Comparison of FRP Human Inner Ear Response - 9mm at the Ear (Log Scale)
Figure 4 presents the results of a second inner ear analysis performed using measured sound overpressure waveforms from the tests; this time, the curves are averages of the analysis from the five shots in each test. On the left, Fig 4a shows the response on the vertical axis with a linear scale. Fig 4b shows the same data on a logarithmic scale. Note that the data is again normalized. At the shooter’s ear, when considering a 5-shot average, the MOD9 FS may have a sound signature approximately 5% less intense than that of the Trident-9. The sound signature of the Obsidian 45 may be approximately 33% less intense than that of the Trident-9.
Fig 4a. Comparison of Average Human Inner Ear Response - 9mm at the Ear (Linear Scale)
Fig 4b. Comparison of Average Human Inner Ear Response - 9mm at the Ear (Log Scale)
PEW Science Research Note: In the five-shot average analysis the high-frequency bias of the Trident-9 is still somewhat discernable above 5,000 Hz. This analysis of measured test data correlates with anecdotal observations of the SWR Trident-9 being perceived as having a “higher pitched” sound signature to the shooter, on average. This observed anecdotal correlation is the subject of continued PEW Science research interest.
6.9.3 Research Supplement Summary
Overall Summary: The Trident-9 exhibits the superior FRP performance of the three silencers, at both the muzzle and ear. The MOD9 FS exhibits the superior average muzzle performance (which correlates to bystander perception). The Obsidian 45 exhibits the superior average ear performance (which correlates to shooter perception). The MOD9 earns the highest suppression rating on the weapon system due to its combination of overall muzzle and ear performance. The SWR Trident-9 seems to exhibit a “higher pitched” sound signature as shown in analytical human inner ear modeling and perceived anecdotally by shooters and bystanders.
This supplement is part of ongoing PEW Science small arm weapon system sound signature research. PEW Science thanks you for your support.
