SSS.6.21 - Research Supplement: Helios QD, Sandman-Ti, and Thunder Chicken Further Analysis
/CGS Helios QD, Dead Air Sandman-Ti, and Q Thunder Chicken on a .308WIN Bolt Action Rifle with 20-inch Barrel
The previous Sound Signature Reviews of the CGS Helios QD (6.13), Dead Air Sandman-Ti (6.19), and Q Thunder Chicken (6.20) presented typical sound signatures of the silencers on a .308 bolt-action rifle with an 20-inch barrel. In PEW Science testing, the Helios QD achieved a Suppression Rating of 44.5. The Sandman-Ti achieved a rating of 41.5. The Thunder Chicken also achieved a rating of 41.5. Detailed muzzle and ear Suppression Ratings of the silencers are provided in the respective reviews.
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.
The three silencers in this comparative analysis were included based upon their similar or overlapping categories of physical characteristics and performance parameters, such as length, weight, suppression, and back pressure.
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 Q Thunder Chicken exhibits superior muzzle performance (which correlates to bystander perception) on average, but the CGS Helios QD is superior in FRP at the muzzle. The Helios QD exhibits superior at-ear performance (which correlates to shooter perception) in both FRP and on average. The Dead Air Sandman-Ti is louder at the muzzle than the Thunder Chicken and the Helios QD, but has slightly better average at-ear performance than the Thunder Chicken, albeit with a higher pitch. The Helios QD earns the highest Suppression Rating overall, and seems to exhibit a “lower pitched” sound signature than the other two silencers during FRP, as shown in analytical human inner ear modeling.
FRP Summary:
When paired with a .308 bolt-action rifle with a 20-in barrel, the Q Thunder Chicken may have an FRP up to approximately 6.6% less intense than that of the Dead Air Sandman-Ti, 1.0 m left of the weapon muzzle. The FRP of the CGS Helios QD may be up to approximately 29% less intense than that of the Sandman-Ti at the muzzle.
At the shooter’s ear, the Sandman-Ti may have an FRP up to approximately 35% less intense than that of the Thunder Chicken, and up to approximately 8.6% more intense than the Helios QD. It is likely that the Sandman-Ti will be perceived by the shooter as louder and higher-pitched than the Helios QD during the first round.
5-Shot Average Summary:
When considering a 5-shot average, the Thunder Chicken may have a sound signature up to approximately 20% less intense than that of the Sandman-Ti, 1.0 m left of the weapon muzzle. The sound signature of the Helios QD may also be up to approximately 20% less intense than that of the Sandman-Ti, but this difference occurs in the lower frequency range- the Helios QD is only approximately 4.5% less intense than the Sandman-Ti in the range of 4,000 Hz. In the high frequency range, the Sandman-Ti and Helios QD sound similar at the muzzle and are both louder than the Thunder Chicken.
At the shooter’s ear, when considering a 5-shot average, the Sandman-Ti may have a sound signature up to approximately 1.6% less intense than that of the Thunder Chicken, but in the higher frequency range, the performance gap reverses, where the Thunder Chicken may be approximately 3.8% less intense than the Sandman-Ti. The sound signature of the Helios QD may be approximately 27% less intense than that of the Thunder Chicken, but above 10,000 Hz is actually up to 2.5% more intense.
6.21.1 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.
PEW Science Research Note: As stated in previous Research Supplements, it is important not misconstrue the frequency-domain data in this Research Supplement 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.
6.21.1.1 FRP Muzzle Comparisons
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 Sound Signature Reviews 6.13, 6.19, and 6.20. 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. Fig 1a shows the response on the vertical axis with a linear scale. Fig 1b and Fig 1c show the same data on a logarithmic scale, in the low and high frequency hearing response regimes, respectively. 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 Q Thunder Chicken may have an FRP up to approximately 6.6% less intense than that of the Dead Air Sandman-Ti. The FRP of the CGS Helios QD may be up to approximately 29% less intense than that of the Sandman-Ti at the muzzle.
Note that In the low frequency response regime, the Thunder Chicken is the quietest during the first shot, whereas the Helios QD is the loudest, which may exaggerate the impression of “lower tone.” In the mid to high frequency regimes, where the human inner ear exhibits the greatest sensitivity, the Helios is the quietest at the muzzle during the first shot, but at the highest frequencies, the Thunder Chicken is the quietest.
Fig 1a. Comparison of FRP Human Inner Ear Response - .308 at the Muzzle (Linear Scale)
Fig 1b. Comparison of FRP Low Frequency Human Inner Ear Response - .308 at the Muzzle (Log Scale)
Fig 1c. Comparison of FRP High Frequency Human Inner Ear Response - .308 at the Muzzle (Log Scale)
6.21.1.2 Five-Shot Average Muzzle Comparisons
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 of the five shots in each test. Fig 2a shows the response on the vertical axis with a linear scale. Fig 2b and Fig 2c show the same data on a logarithmic scale, in the low and high frequency hearing response regimes, respectively. Note that the data is again normalized. When considering a 5-shot average, the Thunder Chicken may have a sound signature up to approximately 20% less intense than that of the Sandman-Ti, 1.0 m left of the weapon muzzle. The sound signature of the Helios QD may also be up to approximately 20% less intense than that of the Sandman-Ti, but this difference occurs in the lower frequency range- the Helios QD is only approximately 4.5% less intense than the Sandman-Ti in the range of 4,000 Hz. In the high frequency range, the Sandman-Ti and Helios QD sound similar at the muzzle and are both louder than the Thunder Chicken.
Fig 2a. Comparison of Average Human Inner Ear Response - .308 at the Muzzle (Linear Scale)
Fig 2b. Comparison of Average Low Frequency Human Inner Ear Response - .308 at the Muzzle (Log Scale)
Fig 2c. Comparison of Average High Frequency Human Inner Ear Response - .308 at the Muzzle (Log Scale)
PEW Science Research Note: There is a high frequency bias noted at the muzzle during the FRP of the Helios QD that may be perceived by bystanders as higher-pitched but there is also a low frequency bias that may overwhelm that perception, depending on the hearing response capability of the individual bystander. After FRP, this bias is still present, but the Sandman-Ti will most likely still be perceived as louder than the Helios. After FRP, the Thunder Chicken will most likely be perceived by bystanders to be the quietest of the three silencers.
6.21.2 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.
6.21.2.1 FRP Ear Comparisons
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. Fig 3a shows the response on a linear vertical scale. Fig 3b and Fig 3c show the same data on a logarithmic vertical scale, in the low and high frequency hearing response regimes, respectively. To personnel firing the weapon, the Sandman-Ti may have an FRP up to approximately 35% less intense than that of the Thunder Chicken, and up to approximately 8.6% more intense than the Helios QD. It is likely that the Sandman-Ti will be perceived by the shooter as louder and higher-pitched than the Helios QD during the first round.
Note the bias in the sound signature of the Sandman-Ti at 4,000 Hz and above. At very high frequencies during FRP, the Sandman-Ti may be perceived by the shooter to be louder than the Thunder Chicken. The slight reduction in inner ear response from the Thunder chicken in the very high frequency regime also occurs at the muzzle, showing frequency spectrum bias consistency.
Fig 3a. Comparison of FRP Human Inner Ear Response - .308 at the Ear (Linear Scale)
Fig 3b. Comparison of FRP Low Frequency Human Inner Ear Response - .308 at the Ear (Log Scale)
Fig 3c. Comparison of FRP High Frequency Human Inner Ear Response - .308 at the Ear (Log Scale)
6.21.2.2 Five-Shot Average Ear Comparisons
Figure 4 presents the results of a second inner ear analysis performed using measured sound overpressure waveforms at the shooter’s ear from the tests; this time, the curves are averages of the analysis from the five shots in each test. Fig 4a shows the response on the vertical axis with a linear scale. Fig 4b and Fig 4c show the same data on a logarithmic vertical scale, in the low and high frequency hearing response regimes, respectively. Note that the data is again normalized. At the shooter’s ear, when considering a 5-shot average, the Sandman-Ti may have a sound signature up to approximately 1.6% less intense than that of the Thunder Chicken, but in the higher frequency range, the performance gap reverses, where the Thunder Chicken may be approximately 3.8% less intense than the Sandman-Ti. The sound signature of the Helios QD may be approximately 27% less intense than that of the Thunder Chicken, but above 10,000 Hz is actually up to 2.5% more intense.
Fig 4a. Comparison of Average Human Inner Ear Response - .308 at the Ear (Linear Scale)
Fig 4b. Comparison of Average Low Frequency Human Inner Ear Response - .308 at the Ear (Log Scale)
Fig 4c. Comparison of Average High Frequency Human Inner Ear Response - .308 at the Ear (Log Scale)
PEW Science Research Note: In the five-shot average analysis the high-frequency bias of the Sandman-Ti is still discernible to the shooter above 4,000 Hz. This analysis of measured test data indicates that the Sandman-Ti may be perceived as having a “higher pitched” sound signature to the shooter, on this weapon system. This conclusion is not immediately obvious when examining data measured at the muzzle alone, except during FRP. This correlation and the potential correlation to anecdotal shooter impressions are both the subjects of continued PEW Science research interest. Overall, the Helios QD is the quietest silencer to the shooter, and only in rare cases would be expected to be perceived as louder. For example, due to its higher muzzle sound signature than the Thunder Chicken, nearby reflecting surfaces that would increase the perceived sound signature from all silencers may result in the Helios being louder, all other things equal. Analysis of suppressed weapon use in reflecting environments is the subject of future PEW Science research effort.
6.21.3 Research Supplement Summary
Overall Summary: The Q Thunder Chicken exhibits superior muzzle performance (which correlates to bystander perception) on average, but the CGS Helios QD is superior in FRP at the muzzle. The Helios QD exhibits superior at-ear performance (which correlates to shooter perception) in both FRP and on average. The Dead Air Sandman-Ti is louder at the muzzle than the Thunder Chicken and the Helios QD, but has slightly better average at-ear performance than the Thunder Chicken, albeit with a higher pitch. The Helios QD earns the highest Suppression Rating overall, and seems to exhibit a “lower pitched” sound signature than the other two silencers during FRP, as shown in analytical human inner ear modeling.
This supplement is part of ongoing PEW Science small arm weapon system sound signature research. PEW Science thanks you for your support.
