user: Question: Who narrated the lap-by-lap to a 13.4 million audience?
Columns: ['Year', 'Network', 'Lap-by-lap', 'Color commentator(s)', 'Pit reporters', 'Host', 'Ratings', 'Viewers']
Types: ['real', 'text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [1979.0, 'CBS', 'Ken Squier', 'David Hobbs', 'Ned Jarrett Brock Yates', 'Ken Squier', '10.5/29', '15.1 million']
SQL:

assistant: SELECT "Lap-by-lap" FROM "Table" WHERE "Viewers" = '13.4 million';