Figure 7.

2D-AMi spectra computed by a gross model of Zebra Finch auditory system for a corpus of five natural soundscapes recorded in distinct terrestrial biomes on different continents at dawn/early morning. From left to right, and top to bottom: a boreal forest, a tropical forest, a temperate forest, a desert and a savannah. Model parameters: (F. Theunissen, personal communication). Audible bandwidth was limited to the 0.5–9 kHz range (Amin et al., 2007). To facilitate comparison with humans 2D-AMi spectra (Figure 2), the output of filters was set to zero for all components outside the audible range. Frequency selectivity was estimated as being twice poorer than for humans (Henry & Lucas, 2010): the width of peripheral audio filters, estimated using the ERB (equivalent rectangular bandwidth) scale, was enlarged by a factor 2 compared to humans (Moore, 2007). As for humans, a modulation filterbank with a quality factor Q of 1 (i.e., 1-oct wide modulation filters) was used to model temporal-envelope processing; however, the highest best modulation rate of modulation filters was set to 100 Hz - compared to 150 Hz for humans (Amin et al., 2010; Woolley et al., 2005). See Figure 2 for legend details and for a comparison with human 2D-AMi spectra.