What cone-shaped wave pattern is made by a source moving faster than wave speed? It is a Mach cone. The pattern forms when a source travels through a medium faster than disturbances can spread through that medium, causing wavefronts to pile up along a cone behind the source.
The classic example is a supersonic aircraft moving through air. Each point along its flight path emits pressure disturbances that travel outward at the local speed of sound. Because the aircraft outruns those disturbances, the wavefronts intersect along a sharp shock-wave surface rather than spreading evenly ahead of the aircraft.
The cone’s half-angle depends on the Mach number, the source speed divided by the local wave speed. In a simple uniform medium, the sine of the half-angle equals the reciprocal of the Mach number. Faster motion therefore produces a narrower cone.
A sonic boom is the audible result when this shock-wave pattern reaches an observer on the ground. A Mach cone is not the same as a light cone, which belongs to relativity, and it is not an Airy disk or Fresnel zone, both of which describe different wave phenomena.