Perhaps you should try some spelling variations:
"sound generation radar" » "second generation radar", "based generation radar", "sound generation raman", "sound generation random", "sound generation rotary"
"sound generation radio" » "second generation radio", "based generation radio", "sound generation audio", "sound generation rapid", "sound generation rabin"
"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 generation radio"))) OR ("sound generating random"))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"sound generation radar\") OR (\"sound generation radio\"))) or (\"sound generating random\"))*".
• Removing quotes may allow a broader search: (((( sound generation radar ) OR ( sound generation radio ))) or ( sound generating random ))*.