How far can a RescueMePhone message be sent with a hammer through stone or rubble?
To send a message using the RescueMePhone application, the person trapped in the rubble hammers a percussive pulse each time the application beeps and flashes. Hammering a stone against some part of the rubble or blowing a loud whistle creates this percussive pulse. The sound of the hammering passes through the air gaps in the rubble and can be heard by the rescuer on the surface, or the seismic wave created by the hammering passes through the rubble and is detected by a seismometer on the surface. Seismic pulses can travel a considerable distances and studies commissioned by the U.S. government have shown that banging on the roof of a mine with a timber can be hear a half mile away. While sending a message by hammering the mine ceiling with a timber or blowing a rescue whistle (man overboard/avalanche ski whistle) under an earthquake is not a fast communications system, it is the only chance to send a message through the rubble to the surface without using high powered equipment. The
