Mach Number
Definition
The ratio of a projectile's speed to the ambient speed of sound; a Mach number greater than 1 indicates supersonic flight and the presence of a Mach-cone shock wave.
- Definition
- Projectile speed divided by local speed of sound
- Supersonic threshold
- Greater than 1
- Below 1
- Subsonic, no Mach-cone shock wave
- Relevance
- Gunshot acoustic and ballistic analysis
Common questions
How does Mach number relate to the Mach cone in analysis?+
Mach number is the underlying ratio that determines whether a shock wave exists at all, while the Mach cone is the physical geometric consequence, its half-angle, that investigators actually measure or infer from a recording once supersonic flight is established.
Does ambient temperature affect the calculation?+
Yes, because the speed of sound in air varies with temperature, the same projectile velocity corresponds to a slightly different Mach number on a cold day than on a hot one, which matters for precise acoustic reconstructions.
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