SASLab Manual
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Real Time Spectrograph : Record > Automatic Recording
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On the real-time spectrogram display it is possible to save acoustic events automatically using the Automatic Recording tool. Each time the input signal exceeds a predefined amplitude threshold within a given frequency interval, a new T*.WAV file is generated, and the incoming audio data will be stored for a predefined hold time into that file. If the threshold is exceeded again within that hold time, the recording will be extended until there is no further threshold exceeding detected.
Automatic event recording into .wav file This check box enables the automatic recording mode. Even if this option is disabled, the trigger status (TRG) will be displayed on the top of the real-time spectrogram window, which can be useful for adjusting trigger.
Autotransfer event waveform If this option is activated, each detected event is transferred automatically into the main window. This option supports real-time classification, if additionally the main window option Actions > On new sound file > Create spectrogram is activated.
Autotransfer event spectrogram If activated, each detected event is transferred automatically into the spectrogram window (as a spectrogram only). This option supports real-time classification. In contrast to the above option Autotransfer event waveform, the spectrogram option does not require to recalculate the spectrogram, which may accelerate the classification process.
Trigger
Threshold The threshold for triggering is expected in percent of the measurement range (full scale). Low values will make the system more sensitive for soft signals. The threshold should be selected carefully. If that value is too small, you will get a lot of undesired recordings caused by other soft disturbances. If the value is too large, you may loose recordings you are interested in because the signal level was below the threshold. To adjust the threshold, you should try different settings while automatic recording is disabled. A recognized trigger event is indicated by the string ”TRG” on the top of the real-time spectrogram window.
Frequency domain
In order to exclude unwanted noise signal, the threshold comparison can be limited to a certain frequency interval.
Note that the frequency resolution of the trigger is determined by the selected FFT length, which means that only frequency differences that are visible on spectrogram can be distinguished by the trigger.
Hold time Each time the threshold is exceeded, a file with at least that duration (hold time) will be generated. If a new trigger event occurs within that hold time, the recording will be continued until there is no further trigger event detected. The hold time should be set as small as possible in order to keep the recording files short.
Minimum duration In order to prevent saving undesired short events (spike-shaped signals), the minimum duration of a trigger event can be specified here. In case the event is shorter than this duration, the file is skipped and will be overwritten by the next one (the file number will not be incremented after closing the file). The default value is zero, which means that all events will be saved regardless of their duration.
File name The file name of the next recording file is displayed here. The file name consists of a leading ”T” followed by a sequential number and the extension *.wav. The serial number is incremented after each recording. If the option Save all events into a single file is activated, this edit field allows editing the .wav file name for storing the events.
The files will be saved into the directory, which was used for the last save operation (by default the Avisoft Bioacoustics data directory).
Reset This button resets the internal file counter to one. The name of the next file will then be T0000001.WAV. As a result, old files may be overwritten.
Save all events into a single file If this option is activated, the events will be stored into a single .wav file (instead of saving them into individual sequentially numbered files). The file name under which the events will be must be specified in the edit field File name. Each new event will be appended to the end of existing file. The option Insert break marks will insert a short full-scale pulse into the .wav file after each event, which allows identifying the single events.
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