Pro - Version 8'
- Sound Sweep -
Effective Large-Area Ground Search Procedure
Sound Sweep vs Low-Visibility Sweep
'Incident Commander Pro's Sound Sweep Routine is a highly effective search method for finding a responsive subject, permitting up to a 3 times larger search area than visual ground searches with the same manpower. It is also a practical night-search and low visibility search technique.
Sound sweeps utilize sound attraction, in combination with wide searcher spacing, to quickly search large areas. The Sound Sweep therefore is an important tool for SAR responders, both for large area searching and for initial trail searches.
The Sound Sweep technique is based upon the assumption that a missing person will respond with sound, usually by shouting, if he/she hears a loud sound generated by the searchers. This means that the Sound Sweep should be conducted as soon as possible after notification, while the subject is still capable of an audible (shouted) response.
'Incident Commander Pro' - Sound Sweep Generator
A base radio station, prompted by 'Incident Commander Pro', is used to synchronize searchers whistle-blasts.
To conduct the Sound Sweep all searchers must have a whistle, radio, map and compass.
The searchers move to their starting points along the baseline, mark this location, and then follow a direction of travel (bearing) through the search area.
The searcher spacing depends on the selected probability of detection (POD) and terrain type, chosen from 'Incident Commander Pro's Sound Sweep Data.
'Incident Commander Pro's integrated Sound Sweep procedure generates synchronized sound prompts, for a wide range of pre-defined terrain types.
'Incident Commander Pro' - Sound Sweep Data
Sound Sweep Procedure:
The 'Incident Commander Pro' sound prompts are used by the base radio to synchronize the searchers whistle blasts, typically once every one to two minutes, depending on the Sound Sweep Data.
At each sound prompt the base radio broadcasts “4,3,2,1, BLAST”
The searchers then stop, cover their ears (to preserve hearing), simultaneously blow their whistles on BLAST, uncover their ears and listen carefully, during 5 seconds of radio silence, for an audible response (shout) from the subject.
The searchers should remain still and quiet as they listen for a response, as any other noise may drown out a faint response sound from the subject.
If no audible response is heard the searchers then continue along their bearing until the next timed sound prompt is heard.
This sound sweep procedure is repeated until the entire area has been searched.
Note: The 1-2 minute sound prompt interval delivers a 100% probability that searchers should hear (detect) an audible response. If this interval is doubled (not recommended) then the Sound Sweep may only deliver a lower 85% Probability of Detection.
Sound Sweep Procedure: Trails
Search teams travelling along trails have their whistle blasts co-ordinated by the sound prompt in much the same way as searchers travelling through a search area. The synchronized whistle blasts along the trail increase both the probability of detection and the corridor-width, often well beyond the limits of visibility. Only one radio per trail team is required.
The recommended trail sound prompt interval is typically 30 seconds to one minute, depending on the Sound Sweep Data.
Doubling the interval between these frequent whistle blasts is not recommended as it will reduce the search corridor-width and the 100% probability of detection down to 85%.
Sound Sweep Procedure: Roads
Vehicles equipped with VHF radios may also perform sound sweeps.
The convoy of vehicles are stopped, each 1 km apart, and simultaneously sound their horns on hearing the sound prompt.
The drivers then listen for a response (shout), then drive 0.1 km up the road, stop and wait for the next sound prompt to sound their horns.
The drivers then listen for a response before driving the vehicle another 0.1 km.
These horn/listen/drive steps are repeated until each vehicle has driven 1 km, at which time the entire convoy moves up to a new section of road and repeats the steps.
Sound Sweep Comments:
As the Sound Sweep procedure relies heavily on communications unnecessary radio chatter should be kept to a minimum, particularly during the sound prompt and the following five seconds of radio silence. While normal radio communications between these prompts is acceptable no chatter should be permitted during the prompts and the following five seconds of radio silence.
Copyright 2016 Martin Colwell. SAR Technology Inc.
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SAR Technology Inc.
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