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==== Infrasound sensitivity ====
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 Hz with a threshold of 65dB. A shallow slope decreased to the best response at 1 kHz with a threshold of 8dB, followed by a steep threshold increase above 4 kHz. According to the 60dB cut-off, the upper limit was 10.5 kHz with absolutely no detectable response at 14 kHz.<ref name="Heffner & Heffner 1980" /> The upper limit for humans is considered to be 18 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 kHz, the average upper limit is 55 kHz.<ref name="Heffner & Heffner 1980" />
The ability to differentiate frequencies of two successive tones was also tested for this elephant using a similar conditioning paradigm. The elephant’s responses were somewhat erratic, which is typical for mammals in this test.<ref name="Heffner & Heffner 1980" /> Nevertheless, the ability to discriminate sounds was best at frequencies below 1 kHz particularly at measurements of 500 Hz and 250 Hz.<ref name="Heffner & Heffner 1980" />
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