Which of the following stages is noisier, at the ending of pile driving operation or at the end of pile driving operation?

When the piles are progressively driven into the ground, the pile section above the ground declines. As a result, the degree of damping on the piles increases. Moreover, the area of exposure of piling surface reduces, thereby reducing the area generating noise form piles. Hence towards the end of pile driving operation, the noise level shall be reduced accordingly.

Noise screen shall be installed to tackle the noise problem. Noise screen made of plywood might not be sufficient because it tends to reflect the noise back to the site and increase the reverberation of the site. Instead for the face of noise screen facing the piling operation shall be lined with a layer of sound-absorbing material such as glass fibre. Moreover, openings on noise screen should be avoided because it can substantially reduce the performance of noise screen.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.