TY - JOUR

T1 - Rainforests as concert halls for birds: Are reverberations improving sound transmission of long song elements?

AU - Nemeth, Erwin

AU - Dabelsteen, Torben

AU - Pedersen, Simon Boel

AU - Winkler, Hans

N1 - Keywords acoustic wave propagation, acoustic wave transmission, acoustic wave reflection, acoustic field, acoustic intensity, bioacoustics, biocommunications, architectural acoustics, reverberation, hearing, forestry

PY - 2006

Y1 - 2006

N2 - In forests reverberations have probably detrimental and beneficial effects on avian communication. They constrain signal discrimination by masking fast repetitive sounds and they improve signal detection by elongating sounds. This ambivalence of reflections for animal signals in forests is similar to the influence of reverberations on speech or music in indoor sound transmission. Since comparisons of sound fields of forests and concert halls have demonstrated that reflections can contribute in both environments a considerable part to the energy of a received sound, it is here assumed that reverberations enforce also birdsong in forests. Song elements have to be long enough to be superimposed by reflections and therefore longer signals should be louder than shorter ones. An analysis of the influence of signal length on pure tones and on song elements of two sympatric rainforest thrush species demonstrates that longer sounds are less attenuated. The results indicate that higher sound pressure level is caused by superimposing reflections. It is suggested that this beneficial effect of reverberations explains interspecific birdsong differences in element length. Transmission paths with stronger reverberations in relation to direct sound should favor the use of longer signals for better propagation.

AB - In forests reverberations have probably detrimental and beneficial effects on avian communication. They constrain signal discrimination by masking fast repetitive sounds and they improve signal detection by elongating sounds. This ambivalence of reflections for animal signals in forests is similar to the influence of reverberations on speech or music in indoor sound transmission. Since comparisons of sound fields of forests and concert halls have demonstrated that reflections can contribute in both environments a considerable part to the energy of a received sound, it is here assumed that reverberations enforce also birdsong in forests. Song elements have to be long enough to be superimposed by reflections and therefore longer signals should be louder than shorter ones. An analysis of the influence of signal length on pure tones and on song elements of two sympatric rainforest thrush species demonstrates that longer sounds are less attenuated. The results indicate that higher sound pressure level is caused by superimposing reflections. It is suggested that this beneficial effect of reverberations explains interspecific birdsong differences in element length. Transmission paths with stronger reverberations in relation to direct sound should favor the use of longer signals for better propagation.

U2 - 10.1121/1.2139072

DO - 10.1121/1.2139072

M3 - Journal article

VL - 119

SP - 620

EP - 626

JO - Acoustical Society of America. Journal

JF - Acoustical Society of America. Journal

SN - 0001-4966

IS - 1

ER -