A signal whistle's sound can travel much further than a human voice and other noises even if the perceived level of volume is similar. Using a whistle also requires much less energy than yelling or other means of signaling for rescue.
Not only does this list of signaling techniques provide people with knowledge to be able to signal for help when needed, but it is valuable to individuals who participate in search and rescue missions, either for a career or as volunteers. Reviewing these techniques can help you recognize and understand what to look for when attempting a rescue.
