Safety / Survival / Army Field Manuals / AFM 3-05.70
19-35. Whistles provide an excellent way for close-up signaling. In some documented cases, they have been heard up to 1.6 kilometers (3/4 mile) away. Manufactured whistles have more range than a human whistle.
All text and images from the U.S. Army Field Manual 3-05.70: Survival.
Appearance of these materials here does not constitute or represent endorsement by mongabay.com.
ProbablyHelpful.com is not responsible for inaccurate or outdated information provided by the U.S. Army Field Manual 3-05.70.