Perhaps you should try some spelling variations:
"sound generation radar" » "second generation radar", "based generation radar", "sound generation raman", "sound generation radio", "sound generation random"
"sound generating random" » "sound generated random", "und generation random", "und generative random"

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: (("sound generation radar") OR ("sound generating random")).
• Removing quotes may allow a broader search: (( sound generation radar ) or ( sound generating random )).
• Adding a wildcard symbol may retrieve word variants: (("sound generation radar") or ("sound generating random"))*.