Where does boom collide?

In aeroacoustics a sonic boom is the sharp noise heard on the ground when an aircraft or projectile flies faster than sound, as the pressure disturbances it makes coalesce into shock waves that reach the ear as a near-instant pressure jump, typically an N-shaped wave. Whitham's 1952 The flow pattern of a supersonic projectile gave the theory that predicts the shock structure and the pressure signature from the body's shape and speed. The referent is an acoustic shock phenomenon measured by overpressure and waveform, with no relation to a market expansion or a sailboat's spar.[1]

Unit

The ground overpressure and waveform of the shock from supersonic flight

Recovery means

Not applicable

Measured by

Measured by peak overpressure, the N-wave rise time and duration, and perceived loudness on the ground

In macroeconomics a boom is the expansion phase of the business cycle, when output rises above trend, unemployment falls, and demand runs strong, the upswing that peaks before a downturn. Mankiw's Macroeconomics places the boom within the recurring cycle of expansion and recession around the economy's long-run growth path. The referent is a phase of aggregate economic activity, measured by output gaps and growth rates, with nothing in common with a shock wave or a sail spar beyond the name.[2]

Unit

A phase of above-trend aggregate activity, gauged by the output gap

Recovery means

Not applicable

Measured by

Identified by a positive output gap, above-trend GDP growth, low unemployment, and rising capacity utilisation