You can most certainly produce shock waves and hence sonic booms on the ground from an aircraft at subsonic speed. If the local flow about any part of the airframe goes supersonic a shockwave is formed. The intensity of the boom on the ground is influenced by a wide range of factors such as atmospheric breakdown, temperature, density, humidity. The attitude and any manoeuvre of the aircraft can also have the effect of concentrating the boom (focusing it in a turn for example).
I think it fair to say that these sorts of booms are likely to cause little or no disturbance to folks on the ground. For "full blooded" supersonic flight the rules (>30 miles parallel or divergent from land or 10miles going away from land IIRC) should keep the headlines free from scandal.
As Typhoon becomes more widespread I would expect to see a few more unexpected "did the earth move for you" events.
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