Physical constraints on acoustic communication in the atmosphere: Implications for the evolution of animal vocalizations

Diana monkey long-distance calls: messages for conspecifics and predators

“…Spectral energy is concentrated at frequencies between 100 and 1000 Hz (Whitehead 1987). Attenuation in the upper forest strata is low in this frequency range, leading some to hypothesize that calls within this range are particularly well suited for longdistance communication (Wiley & Richards 1978;Richards & Wiley 1980;Waser & Brown 1984). Thus far, most functional explanations of primate long-distance calls have focused on their role in intraspecific communication (Byrne 1982;Kinzey & Robinson 1981;Sekulic 1982;Snowdon 1986;Tenaza 1989;Gautier & Gautier 1977;Waser 1978).…”

Chickadee songs provide hidden clues to singers’ locations

“…Birds clearly can make use of amplitude cues to judge singer distance in some circumstances (Nelson, 2000;Radziwon et al, 2011). Amplitude cues are less reliable than other distance cues because of amplitude variations caused by factors other than source distance, such as differences in source levels, atmospheric conditions, and height of the singer (Morton, 1982;Wiley & Richards, 1978, 1982. Chickadees trained to discriminate songs recorded from different distances varied in their use of amplitude cues, with some individuals using them and others ignoring them (Phillmore et al, 1998).…”

“…Past considerations of spectral energy as a possible cue for assessing the distance to a singing bird note that higher frequencies often attenuate more rapidly than lower frequencies in bird habitats (Wiley & Richards, 1978). Using spectral attenuation to judge auditory distance requires detailed knowledge of the frequency content of the song at the source.…”

“…Birds use several acoustic cues to do this, including variations in overall amplitude, differential spectral attenuation, and signal distortions associated with reverberation (reviewed by Naguib & Wiley, 2001). Some acoustic features of songs, such as rapid trills, degrade rapidly as they propagate, suggesting that these features may function, at least in part, to provide information about a vocalizing bird's distance from any listening birds (Naguib, 2003;Wiley & Richards, 1978). Judging the distance to a vocalizing individual is complicated by the fact that not all individuals produce sounds at the same intensity or with identical spectrotemporal features; absolute values of received features thus cannot unambiguously reveal a singing bird's location.…”

“…Similarly, by sequentially comparing directly received sounds to the reverberation generated by those sounds, listeners can estimate the range of a sound source without knowing the intensity of the source (Larsen, Iyer, Lansing, & Feng, 2008;Zahorik, 2002). Past assessments of the role reverberation plays in auditory distance estimation by birds have typically focused on how reverberation distorts song features (Dabelsteen, Larsen, & Pedersen, 1993;Fotheringham & Ratcliffe, 1995;Holland, Dabelsteen, Pedersen, & Paris, 2001;Nelson & Stoddard, 1998;Wiley & Richards, 1978). However, reverberation can also enhance long-distance transmission if the energy within sounds is focused within a narrow frequency band (Slabbekoorn, Ellers, & Smith, 2002).…”