amritsar:a loud ''explosion'' heard, here, at about 4 pm on thursday, shook many a heart. many residents panicked, assuming it was an enemy attack, till senior army officials revealed that the ''canon fire-like'' sound was the result of a technical air formation by fighter jets on their routine flight. the officials said that when lowflying jets crossed the speed of sound, a shock barrier was formed. this led to tremendous air pressure, causing sound waves to hit the ground, thus creating the impression of a blast. puri new amritsar dc swinder singh puri has taken over as the deputy commissioner of amritsar, replacing narinderjit singh, according to a press release issued, in amritsar, on thursday.