Acoustic location
It was rendered obsolete before and during World War II by the introduction of radar, which was far more effective (but interceptable).
Microphones have a polar pattern describing their sensitivity as a function of the direction of the incident sound.
Many microphones have an omnidirectional polar pattern which means their sensitivity is independent of the direction of the incident sound.
Instead of estimating a set of time-differences of arrival (TDOAs) between pairs of microphones and combining the acquired estimates to find the source location, indirect methods search for a candidate source location over a grid of spatial points.
In this context, methods such as the steered-response power with phase transform (SRP-PHAT)[5] are usually interpreted as finding the candidate location that maximizes the output of a delay-and-sum beamformer.
The method has been shown to be very robust to noise and reverberation, motivating the development of modified approaches aimed at increasing its performance in real-time acoustic processing applications.
He needed a means of locating Zeppelins during cloudy conditions and improvised an apparatus from a pair of gramophone horns mounted on a rotating pole.
Several of these equipments were able to give a fairly accurate fix on the approaching airships, allowing the guns to be directed at them despite being out of sight.
[9] Although no hits were obtained by this method, Rawlinson claimed to have forced a Zeppelin to jettison its bombs on one occasion.
[11][12] End of the 1920s, an operational comparison of multiple large acoustic listening devices from different nations by the Meetgebouw in The Netherlands showed drawbacks.
Moreover, mechanical prediction equipment, given the slow speed of sound as compared to the faster planes, and height corrections provided information to point the searchlight operators and the anti-aircraft gunners to where the detected aircraft flies.
As World War II neared, radar began to become a credible alternative to the sound location of aircraft.
For typical aircraft speeds of that time, sound location only gave a few minutes of warning.
[8] The acoustic location stations were left in operation as a backup to radar, as exemplified during the Battle of Britain.
[14][dead link] After World War II, sound ranging played no further role in anti-aircraft operations.
[17] Seismic surveys involve the generation of sound waves to measure underground structures.
Source waves are generally created by percussion mechanisms located near the ground or water surface, typically dropped weights, vibroseis trucks, or explosives.
Because the cost of the associated sensors and electronics is dropping, the use of sound ranging technology is becoming accessible for other uses, such as for locating wildlife.
