The only personnel within the 3,000 feet are the launch crew inside the blockhouse and the test counter. Although the alarm has not been given, the time of the alarm must be near the count.
12 seconds sound clip from the Dr. No movie soundboard.
You can hear this line at 01:39:40 in the Blu-ray version of the movie.
Quote context
[...]
- Have you got new fuel elements loaded?
- We will run up to half-power for 30 seconds.
- Control interlocks free. Fuel elements 12.5.
- Control?
- Control rod actuators operating. Core temperature, 113.
- Converters standing by. Ignition meters on.
[...]