Perception of infrasound: Difference between revisions

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There are some confounding factors that might influence the results of this kind of experiment. Firstly, the animals might actually be more sensitive than the experiments would indicate owing to [[habituation]] of the animals to the playback stimuli after several trial repetitions. To avoid this, researchers present several different types of playbacks in random order. Another problem that might arise in interpreting field experiments done on groups of animals is that animals may be responding to signals from other elephants in the group rather than the playback stimulus. However, an assumption is made that at least one animal in the group did perceive and respond directly to the stimulus.<ref name="Langbauer et al 1990" /><ref name="Langbauer et al 1991" />

==== Infrasound sensitivity ====

==== ultrasonic

The auditory sensitivity thresholds have been measured behaviorally for one individual young female Indian elephant. The [[Classical conditioning|conditioning]] test for sensitivity requires the elephant to respond to a stimulus by pressing a button with its trunk, which results in a sugar water reward if the elephant correctly identified the appropriate stimulus occurrence.<ref name="Heffner & Heffner 1980">{{cite journal|last=Heffner|first=H.|coauthors=R. Heffner|title=Hearing in the elephant (Elephas maximus)|journal=Science|year=1980|volume=208|pages=518–520}}</ref> To determine auditory sensitivity thresholds, a certain frequency of sound is presented at various intensities to see at which intensity the stimulus ceases to evoke a response. The auditory sensitivity curve of this particular elephant began at 16&nbsp;Hz with a threshold of 65dB. A shallow slope decreased to the best response at 1&nbsp;kHz with a threshold of 8dB, followed by a steep threshold increase above 4&nbsp;kHz. According to the 60dB cut-off, the upper limit was 10.5&nbsp;kHz with absolutely no detectable response at 14&nbsp;kHz.<ref name="Heffner & Heffner 1980" /> The upper limit for humans is considered to be 18&nbsp;kHz. The upper and lower limits of elephant hearing are the lowest measured for any animals aside from the pigeon.<ref name="Heffner & Heffner 1980" /> By contrast, the average best frequency for animal hearing is 9.8&nbsp;kHz, the average upper limit is 55&nbsp;kHz.<ref name="Heffner & Heffner 1980" />