Loud sound rattles Bengaluru; Defence Dept admits it's 'sonic boom'

A loud noise, similar to a sonic boom, brought jitters to residents across eastern and southern parts of Bengaluru on Wednesday afternoon with the Defence Department admitting late in the night that the sound was caused by a test flight.

Speculations poured in immediately after the incident occurred around 1.15-1.40 pm, with some calling it an earthquake and others fearing an explosion. Residents from areas in about 40 sq km from central Bengaluru to Whitefield in the east and Yelahanka in the north; to Electronic City in south and areas beyond Marathahalli claimed to have heard the noise.

At least two persons told DH that windows rattled during the incident which did not last more than three seconds. MG Road, Shantinagar, Jayanagar, Indiranagar, Basvanagudi in central Bengaluru reported the incident. Many took to social media to express their shock.

“I was inside my car near Indiranagar KFC when the vehicle shook mildly after a loud blast-like sound. I almost jumped out and saw several people looking at the sky,” Selva Kumar, an Uber taxi driver, told DH.

Karnataka State Natural Disaster Monitoring Centre (KSNDMC) Director Srinivasa Reddy earlier clarified that the noise was not caused by earthquake or any weather phenomenon. “We do not know the source of the sound. But we can confirm that it is not connected with any subsurface event,” he said, dismissing rumours of an earthquake as the “seismometers capture vibrations of even mild tremor".

“Bengaluru has a hard rock terrain and subsurface activity does not occur in such places. From what we hear, the sound is too big to be caused by weather phenomena. It seems more like an ultrasonic activity," he said.

The Defence Department confirmed that the sound was a sonic boom. The Bengaluru public relations office of the Ministry of Defence tweeted, "the sonic boom was probably heard...while an aircraft of supersonic profile was decelerating from supersonic to subsonic speed between 36,000 and 40,000 feet altitude."

It said the plane took off from "Bengaluru Airport and flew in the allotted airspace well outside city limits. The aircraft was of ASTE, whose test pilots and flight test engineers routinely test out all airplanes. The aircraft was far away from the city limits when this occurred," the tweet said.

When it was pointed out that nearly half of Bengaluru was rattled by the sound, the spokesperson told DH that an investigation is being conducted to understand exactly what happened. "The sound of a sonic boom can be heard even when the aircraft is flying as far as 65 to 80 km away. Certain weather phenomena may also amplify its effect," he said.

To a question on the possibility of breaking the sound barrier within city limits, the spokesperson said there were clear protocols governing the testing: "A clear picture will emerge once the investigation is completed."

This is the second such incident being reported in the city in recent years. The cause of a similar sound heard on Aug. 16, 2018, in southern and western parts of the city, has remained a mystery.