The sound pressure level of gunshots can exceed 140 dB and can consequently cause hearing damage. Sound suppressors can be used to lower the sound pressure level by 20 dB and more. Typical sound suppressor lower the sound level by mixing expanding gunpowder gases and by breaking up the initial muzzle blast, while spiral Helmholtz suppressors (SHS), also called spiral Helmholtz resonators, use the resonance of gases in a narrow spiral tube, which causes viscous losses. In our thesis we designed and 3D printed multiple spiral Helmholtz resonators with different resonance frequencies and measured their ability to dampen bangs with the use of a loudspeaker. We measured their resonance frequencies and compared them to the ones we calculated - these deviated, on average, by less than 7 %. We then assembled a cascade SHS with resonance frequencies between 400 and 900 Hz with a spacing of 25 Hz and tested it with a small calibre rifle. Compared to a rifle without any suppressor, it lowered the maximum sound pressure level LCPKmax by 20,7 dBc. The sound levels LAFmax of all frequency bands from 6,3 Hz up to 20 kHz were lowered, on average, by 9,7 dBa. Time domain
measurements showed that our commercial and cascade SHS suppressors changed the gunshot in both the time and frequency domain, such that its shape no longer conformed to the Fireldander wave, implying that both types of suppressors helped break up the initial muzzle blast.
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