Yes, the noise level is measured on the ground directly below the flight path of the plane. Interestingly, it’s not just the volume but also the pattern of the

Yes, the noise level is measured on the ground directly below the flight path of the plane. Interestingly, it’s not just the volume but also the pattern of the boom that can be altered by changing the design of the plane. There’s a great discussion of this here: https://www.elidourado.com/p/50-years-supersonic-ban https://www.elidourado.com/p/50-years-supersonic-ban (Scroll down to the images of the sound wave)