F-15 Eagle Quiet Spike

The 24-foot-long "Quiet Spike" sonic boom mitigator mounted on the nose of NASA's F-15B test bed was developed by Gulfstream Aerospace as a means of controlling and reducing the sonic boom caused by an aircraft flying faster than sound.

https://www.nasa.gov/centers/armstrong/news/FactSheets/FS-055-DFRC.html