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Detection of animals through the bioacoustics method has been popularised lately. The key terms that we heard in bioacoustics research are PAM and AAM. What is the difference between PAM and AAM? where it is applicable?

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2 Answers 2

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In AAM or Active Acoustics Monitoring, Either we use Acoustics Energy to detect animals (mostly applicable to aquatic animals/fish), or We use the playback method to get responses from the species (Mostly applicable for animals who have territorial calls).

In PAM or Passive Acoustics Monitoring, we don't emit any energy or stimulus. We record the natural animal calls mostly using Automated devices. This is mostly applicable for species that have echolocation or vocally very active.

e.g. Howling survey for detecting wolves is AAM Method. whereas if we monitor the wolves through Automated Recording Units (ARUs) without any stimulus calls (/Playback) it is considered as PAM.

Most marine mammals are detected through ARU hydrophones. Bat is another terrestrial species that can be easily detected through a PAM device.

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The simple answer would be

  • AAM, like active sonar, emits sound to detect the species of interest
  • PAM only listens to the sound made by the species of interest

Advantages of AAM is that it may detect species that are silent.

Disadvantages include that in order for AAM to work is that the species of interest reflects significant portion of incoming sound (keyword target strength). Fish with air-filled bladders are prime candidates for AAM (or fish-finding sonar). Deep diving Marine mammals with collapsed lungs are examples where AAM is not so efficient.

In my opinion, AAM should not be used where the species is or could be negatively impacted by the active sound source. The use of Active sound sources to elicit responses from the species of interest may or may not have negative impact, depending on the species and type of sound exposure.

PAM is very efficient if the species of interest emit sound, but of less use if they remain silent.

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