Outsourced hearing in spiders by using their webs as auditory sensors

Hearing is a fundamental sense of many animals, including all mammals, birds, some reptiles, amphibians, fish and arthropods1,2. The auditory organs of these animals are extremely diverse in anatomy after hundreds of millions of years of evolution3-5, yet all are made up of cellular tissue and are embodied meaning that its functional anatomy is constrained by developmental morphogenesis. Here we show hearing in the orb-weaving spider, Larinioides sclopetarius is not constrained by embodiment but is extended through outsourcing hearing to its proteinaceous, self-manufactured orb-web, and hence under behavioral control, not developmental biology. We find the wispy, wheel-shaped orb-web acts as a hyperacute acoustic array to capture the sound-induced air particle movements that approach the maximum physical efficiency, better than the acoustic responsivity of all previously known ears6,7. By manipulating the web threads with its eight vibration-sensitive legs8-10, the spider remotely detects and localizes the source of an incoming airborne acoustic wave emitted by approaching prey or predators. By outsourcing its acoustic sensors to its web, the spider is released from embodied morphogenetic constraints and permits the araneid spider to increase its sound-sensitive surface area enormously, up to 10,000 times greater than the spider itself11. The use of the web also enables a spider the flexibility to functionally adjust and regularly regenerate its 'external ear' according to its needs. This finding opens a new perspective on animal hearing - the 'outsourcing' and 'supersizing' of auditory function in a spider, one of the earliest animals to live on land12. The novel hearing mechanism provides unique features for studying extended and regenerative sensing13-15, and designing novel acoustic flow detectors for precise fluid dynamic measurement and manipulation16-18.

A Partition Spatial Filtering Method for Acoustic Array Configuration

Acoustic array is a ubiquitous tool for locating and quantifying sound sources. However, its effectiveness depends greatly on the array configuration. This paper presents an array configuration method to enhance array performance, especially on the spatial resolution and the Doppler effect correction. The problem of array configuration is formulated into a position matrix determined by introducing partition spatial filtering. Irregular coaxial ring grid spacings and partition filtering conditions are suggested to control array spatial resolution. Geometrical parameters and performance indicators are constructed to quantify the relationships between the array configuration and performance. Based on these quantitative relations, the spatial variation of the array beam pattern and the Doppler effect has got adaptive adjustment. In particular, an adaptive partition algorithm is proposed to reduce computation time. The performance of the method is examined numerically and experimentally, which is compared with the other methods. The results provide the method to guide the design of a 64-microphone optimized array with high performance (1.8° spatial angle resolution and 40% Doppler frequency correction over the bandwidth from 800 Hz to 3000 Hz) and fast computing speed (18 s array generated time for 2000 arrays). Furthermore, an unusual feature of the method is that it can be utilized in the case when the source moves at a nonconstant velocity.