SSS.6.5 - Research Supplement: Trash Panda and VOX S Further Analysis
/Q Trash Panda and Energetic Armament VOX S on 20” .308WIN Bolt Action Rifles
The previous Sound Signature Reviews of the VOX S (6.3) and the Q Trash Panda (6.4) presented typical sound signatures of the silencers on typical hunting rifle configurations. In PEW Science testing, the VOX S achieved a Suppression Rating of 29.5 and the Trash Panda achieved a rating of 33.1.
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 two silencers. This supplement is part of ongoing PEW Science small arm weapon system sound signature research.
Summary: When paired with a 20” .308 bolt action rifle and fired with supersonic ammunition, test results indicate that the sound signature of the Energetic Armament VOX S may be approximately 15% less intense than that of the Q Trash Panda to the human ear, 1.0 m left of the weapon muzzle. At the shooter’s ear, the Trash Panda sound signature may be up to 90% less intense than that of the VOX S. This may seem extreme, but is not unreasonable for the sound signature regimes discussed.
6.5.1 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 two previous tests presented in reviews 6.3 and 6.4. The results are an average of individual analyses performed of each shot. 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 two silencers. To personnel located 1.0 m left of the weapon muzzle, the VOX S sound signature may be approximately 15% less intense than that from the Q Trash Panda. 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 Human Inner Ear Response - .308WIN at the Muzzle (Linear Scale)
Fig 1b. Comparison of Human Inner Ear Response - .308WIN at the Muzzle (Log Scale)
6.5.2 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 2 presents an inner ear analysis performed using measured sound overpressure waveforms at the shooter’s right ear from the tests. Again, the results are an average of individual analyses performed of each shot. On the left, Fig 2a shows the response on a linear vertical scale. Fig 2b shows the same data on a logarithmic vertical scale. This time, the normalized data shows significant relative discrepancy. To personnel firing the weapon, the Trash Panda sound signature may theoretically be up to 90% less intense than the VOX S.
Fig 2a. Comparison of Human Inner Ear Response - .308WIN at the Ear (Linear Scale)
Fig 2a. Comparison of Human Inner Ear Response - .308WIN at the Ear (Log Scale)
6.5.3 Research Supplement Summary
When paired with a 20” .308 bolt action rifle and fired with supersonic ammunition, test results indicate that the sound signature of the Energetic Armament VOX S may be approximately 15% less intense than that of the Q Trash Panda to the human ear, 1.0 m left of the weapon muzzle. At the shooter’s ear, the Trash Panda sound signature may be up to 90% less intense than that of the VOX S. This may seem extreme, but is not unreasonable for the sound signature regimes discussed. Recall that the Suppression Rating encompasses total weapon system sound signature performance and is based upon occasional shot doses, which are intended for no more than once per week in a sliding 24-hour period. In practicality, bystanders with unprotected ears may not notice significant difference when the shooter is firing these tested weapon configurations. To the shooter with unprotected ears, the predicted discrepancy in inner ear response may result in less shots being allowed in a 24-hour period with the VOX S.
This supplement is part of ongoing PEW Science small arm weapon system sound signature research. PEW Science thanks you for your support.
