In internally coupled ears, displacement of one eardrum creates pressure waves that propagate through air-filled passages in the skull and cause displacement of the opposing eardrum, and conversely. By modeling the membrane, passages, and propagating pressure waves, we show that internally coupled ears generate unique amplitude and temporal cues for sound localization. The magnitudes of both these cues are directionally dependent. The tympanic fundamental frequency segregates a low-frequency regime with constant time-difference magnification from a high-frequency domain with considerable amplitude magnification.
The use of infrasound for the early detection of volcanic events has been shown to be effective over large distances, and unlike visual methods, is not weather dependent. Signals recorded via an infrasound array often have a poor signal to noise ratio, as other sources of infrasound are detected and recorded along with the volcano infrasound. Array processing software does not always detect known volcanic events, in part because of the amount of noise in the infrasound signal (Taisne et al., in: Pichon, Blanc, Hauchecorne (eds) Infrasound monitoring for atmospheric studies: challenges in middle atmosphere dynamics and societal benefits. Springer International Publishing, Cham, 2019). Resampling the infrasound into the audible range and then applying the acoustic noise reduction techniques of spectral subtraction prior to array processing is shown to improve signal detection of volcanic events. The discussed technique is applicable to any infrasound signal such as infrasound from anthropogenic sources like nuclear testing.
In film important narrative events are sometimes presented by sound alone, leading some audiences to remember seeing events that were not presented visually. Audiences construct a representation of the narrative based on information supplied by the film, integrated with knowledge derived from stored memory schemas, for later recall. However, the ability of off-screen sound to evoke visual memories of unseen narrative events has never been empirically tested in a real-world setting. We played audiences (adults in Singapore and online) two experimentally manipulated versions of a narrative film in which different events were depicted on screen or by sound alone. In a recall test, audiences reported high confidence for having viewed some events that were only presented with sound. Confidence for seen/unseen events differed according to their narrative salience, and audience empathy played a role. These findings are the first demonstration of the psychologically real sound-evoked visual memory in film audiences.
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