Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_17478 ( "Series #" real, "Title" text, "Directed by" text, "Written by" text, "Original air date" text, "Production code" text, "U.S. viewers (millions)" text )

### Question ###
What's the total number of directors who've directed episodes seen by 11.34 million US viewers?

### Accurate SQL ###

SELECT COUNT("Directed by") FROM table_17478 WHERE "U.S. viewers (millions)" = '11.34'