Voice-Calling Detection Distance with a Parabolic Microphone in Land Search and Rescue.

Area of Science:

• Search and Rescue Operations
• Acoustic Detection Technology
• Human Auditory Perception

Background:

• Effective detection of lost persons in search-and-rescue (SAR) operations is critical.
• Auditory search methods are employed, but their range limitations are a challenge.
• Acoustic enhancement devices may improve the effectiveness of auditory SAR sweeps.

Purpose of the Study:

• To evaluate the effectiveness of a 55.9 cm parabolic microphone in increasing detection range during SAR sound sweeps.
• To compare the performance of the parabolic microphone against the unaided ear for locating simulated lost persons.
• To assess the audibility of signaling devices (whistles, train horn) used by a lost person.

Main Methods:

• Five SAR personnel listened for random words shouted by a simulated lost person at varying distances in forest environments.
• Intelligibility distance (50% word understanding) and audibility distance (50% word hearing) were measured with and without the parabolic microphone.
• The audibility of signaling devices by the lost person was tested at the microphone's audibility distance.

Main Results:

• The parabolic microphone increased intelligibility and audibility distances by an average factor of 1.44 compared to the unaided ear.
• A predictive equation for intelligibility distance with the microphone was established based on ambient noise levels.
• Only a portable train horn was audible to all participants using their unaided ear at the microphone's audibility distance.

Conclusions:

• Parabolic microphones significantly extend auditory detection range in SAR operations.
• Combining a parabolic microphone with a train horn offers a 44% greater area coverage rate than unaided searching.
• The parabolic microphone and train horn combination provides approximately 20 times the area coverage of visual searching.