What is a Hush Kit?

We take a look at old-school tech that was applied to airliner engines in the 50s, 60s, and 70s, until the march of technology made them unnecessary.
They were weird, groovy, and vital to comply with the law.
I wish I had one!

Some copy/paste links...

The video that sparked the question:
   • Pan American Boeing 707 Promo Film - ...   at 15:58 aircrew is inspecting the exhaust mixer.

My video called Turbojet or Turbofan:    • Turbojet or Turbofan - Turbine Engine...  

A video about the new "ejector" hush kit for the RR Spey engines in a Gulfstream:
   • Hubbard Aviation Technologies QS3 Hus...  

A great shot of an old Air New Zealand 737 with ejector hush kits ( with thrust reversers ) on it's JT8D engines... https://fb.watch/rKqVt87BhA/