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SASLab Manual

Main window : Analyze > Specials > Time-delay-of-arrival (TDOA) measurements >

It is possible to determine the position of a sound source (e.g. a vocalizing animal) by means of an array of microphones (passive acoustic location). The time differences at which the sound signals arrive at these microphones can be computed by cross-correlation. If the positions of the microphones are known, the position of the sound-source can then be calculated by using a set of hyperbolic equations.

The command Copy single TDOA from marked section computes the delay of a signal that is present in all channels by using a cross correlation technique. Only the marked section will be used for the cross-correlation. The marked section should cover the signal to be measured in all channels. Otherwise, the algorithm will provide wrong results. The multi-channel sound file necessary for two- or three-dimensional location can be created from several mono or stereo wav-files by the command File > Add channel(s) from file. Alternatively, multi-channel files can be imported from external non-wav files acquired by other data acquisition devices (see Import Format for details).

The maximum of the cross-correlation function is searched and its position is taken as the delay between each pair of channels.

The results of the time delay determination between all channels will be copied into the clipboard and can be additionally transferred via DDE into a spreadsheet application like Excel. The delays are represented as floating point numbers (unit 1 second) in the ASCII format. Tabulators separate the single values. If there are more than two channels, the sequence of the values is as follows:

(1-2) (1-3) (2-3) (3 channels: first value is the delay between channel 1 and 2, the second value is the delay between 1 and 3 and third value is the delay between 2 and 3. The first value (2-1) will be positive, if the signal arrives first in channel 1 and then in channel 2.
(1-2) (1-3) (1-4) (2-3) (2-4) (3-4) (4 channels),
(1-2) (1-3) (1-4) (1-5) (2-3) (2-4) (2-5) (3-4) (3-5) (4-5) (5 channels, and so on)

The command Copy multiple TDOA’s from section labels does the same as Copy single TDOA from marked section, except that the computations will be made for all section labels instead of the marked section. CR control characters will separate the results for each label.

TDOA Settings... Launches a dialog box for adjusting TDOA settings.

Avisoft Bioacoustics last modified on 28 March 2022