SSS.6.115 - Research Supplement: Flow-Through Silencers vs. Conventional Silencers. Head-to-Head Detailed Comparison - Nomad-Ti vs. FLOW 762 Ti vs. Thunder Chicken (Article Preview)

Dead Air Nomad-Ti, HUXWRX FLOW 762 Ti, and Q Thunder Chicken on a .308WIN Bolt Action Rifle with 20-inch Barrel

There are a variety of technologies implemented in modern rifle silencers. Principally, silencers reduce the severity of the signature produced by a small arm weapon system by modifying the propagation of combustion gasses such that they enter the ambient atmosphere at a lower temperature and pressure than they would otherwise, had a silencer not been installed on the weapon. These parametric differentials, along with the rate of gas propagation, dictate the resulting suppressed small arm signature.

The severity of a suppressed small arm weapon signature, to the human inner ear, is quantified by the PEW Science Suppression Rating (Figure 1). As the Suppression Rating is a Damage Risk Criterion (DRC), it only expresses the degree to which a human may experience hearing damage. Although complex signature characteristics are included in its computation, the end result is only a DRC. Suppression Rating Rankings can be found in Section 7 of the Standard.

The nature of human inner ear response, and human interpretation of such response, dictates further signature examination if one desires information outside the purposes of DRC use. For example, end users may be interested in “how a silencer sounds,” rather than in the hearing damage risk potential of using the silencer on their weapon. The two phenomena are not necessarily coupled for all users.

The Suppression Rating DRC allows the end user to group silencers with similar hearing damage risk potential on a variety of weapon systems. After such grouping, further analysis can provide insight into the aforementioned phenomena. To that end, three silencers evaluated by PEW Science are included in this members-only Research Supplement to examine relative First Round Pop (FRP) and overall sound signature suppression performance characteristics. The silencers in this group were selected for their very similar holistic sound suppression performance; their similar PEW Science Suppression Rating on a supersonic centerfire bolt action rifle. The three silencers behave differently, despite their similar performance. Silencers with similar suppression performance sometimes have very different flow restriction, or back pressure, partially characterized by the PEW Science Omega Back Pressure Metric (Figure 2). These are three examples of such silencers.

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Fig 1. PEW Science Suppression Rating Scale

The published Sound Signature Reviews of these three silencers, with supersonic ammunition, are linked below:

• Q Thunder Chicken (6.20)

• Dead Air Nomad-Ti (6.44)

• HUXWRX FLOW 762-Ti (6.113)

Because the Suppression Rating is a DRC, it characterizes the postulated risk of hazard to bystanders, or the weapon operator, from a suppressed small arm weapon system. Despite achieving a similar Suppression Rating, some silencers may have certain signature characteristics that differ from others, and those differences are of interest to users, as noted above.

Furthermore, sound suppression performance of centerfire rifle silencers, particularly during the first shot, is of significant concern to many weapon system operators. High sound signature amplitude during the first shot from a suppressed weapon system is referred to as First Round Pop (FRP). Prior to the weapon system being fired, a sound suppressor is filled with air from the surrounding environment; this air occupies the internal silencer volume and supports ancillary combustion during the first shot. It is this ancillary combustion that may increase sound signature relative to subsequent shots. The FRP phenomenon is present and measurable in all suppressed systems unless the internal silencer atmosphere is purged such that ancillary combustion is not supported within the silencer.

Fig 2. PEW Science Silencer Relative Back Pressure Metric, Omega, For 30 Caliber Rifle Silencers

Typically, silencers possessing a very low Omega Metric exhibit lower sound suppression performance, but there are several significant exceptions. Although changes to gross gas flow rate (flow restriction, or back pressure) strongly correlates to sound signature suppression, there are other flow dynamics and frequency components of silencer sound signatures that result in varying signature severity to the human inner ear for a given suppressed system. These gas dynamics can significantly influence some signature characteristics. Furthermore, certain personnel may have preexisting hearing damage or other hearing sensitivity characteristics that differ from the 95th-percentile inner ear response with which the PEW Science Suppression Rating correlates. The impact of these differences on the human perception of silencer sound suppression performance has been quantified by PEW Science.

This 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 three supersonic 308 rifle silencers that possess similar holistic sound suppression performance. Both FRP and total sound signature suppression regimes are examined. This supplement is part of ongoing PEW Science small arm weapon system sound signature research.

The full version of this article is only available to members. You can support PEW Science testing, research, and development with a membership, here. State-of-the-art firearm sound signature testing and research conducted by PEW Science is supported by readers like you. Thank you for your support!