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

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 ("second generation radar"))) OR ("sound generation random"))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((\"sound generation radar\") OR (\"second generation radar\"))) or (\"sound generation random\"))*".
• Removing quotes may allow a broader search: (((( sound generation radar ) OR ( second generation radar ))) or ( sound generation random ))*.