You could absolutely hear the Concorde from the ground, and it was famous for being one of the loudest civilian aircraft ever built. When taking off, its four Rolls-Royce/Snecma Olympus 593 engines used afterburners (reheat), creating a thunderous roar that was significantly louder than modern subsonic jets. However, the most controversial sound associated with the Concorde was the "sonic boom." When the aircraft exceeded the speed of sound (Mach 1), it created a continuous shockwave that trailed behind it. From the ground, this sounded like a sudden, double "bang-bang" that was powerful enough to rattle windows and startle people and animals. Because of this intense noise, the Concorde was banned from flying at supersonic speeds over land in most countries, including the United States and much of Europe. It could only "open up" its engines once it was far out over the Atlantic Ocean. Even at subsonic speeds during its approach and landing, the Concorde had a high-pitched, piercing engine whine that made it easily identifiable to anyone living near Heathrow or JFK airports. The sheer volume of the aircraft was one of the primary reasons it was never able to expand its routes beyond a few specific coastal cities.