E. Kasuya & S. Shiobara (1996). Variation in the advertisement call in the foam-nesting treefrog Rhacophorus arboreus. Bioacoustics 7(1): 1-11
Abstract
Variations in the temporal and spectral characters of advertisement calls by males of the foam-nesting treefrog Rhacophorus arboreus were studied. The advertisement calls had 2 to 6 notes. The interval between notes became longer within a single call. The interval between notes was negatively correlated with temperature but not correlated with body size (snout-vent length, body weight or mouth width). The frequency of a note became higher within a single call. Snout-vent length, body weight and mouth width were negatively correlated with the frequency. However, snout-vent length and body weight were correlated with the frequency of the call in different ways.
Keywords: vocalization, advertisement call, variation, anuran, Rhacophorus arboreus
P.J. Fonseca (1996). Sound production in cicadas: timbal muscle activity during calling song and protest song. Bioacoustics 7(1): 13-31
Abstract
Electromyograms (EMGs) of the timbal muscles were recorded during the calling songs and 'protest songs' (also referred to as alarm signals) in five species of cicadas: Cicada barbara lusitanica, Tettigetta josei, Tettigetta argentata, Tibicina quadrisignata and Tympanistalna gastrica.
The timbal muscle contraction rates of all species ranged from 50 to 250 Hz. The basic timbal cycle generating sound during the inward and outward buckling of the timbal was maintained in calling song and protest song for all five species. Comparison of the temporal parameters and the corresponding timbal muscle activity in both sound signals revealed that the timbal muscle period as well as the intertimbal delay showed the same mean values. Major differences between calling song and protest song are apparent in the pattern determining schemes and phrases as well as in the sound amplitude modulation.
The amplitude of the sound pulse during the inward movement of the timbal was positively correlated with the time lag from the timbal muscle activity to the IN sound pulse in the calling songs of Tettigetta josei, Tettigetta argentata and Tympanistalna gastrica, species with a one-to-one correspondence between a single contraction of the timbal muscle and the production of a sound pulse as the timbal buckles inwards. These relationships did not hold for the other two species, where a single contraction of the timbal muscle causes the timbal to buckle inwards in steps to produce a train of sound pulses. This indicates the presence of different mechanisms responsible for sound amplitude modulation. There was no evidence that the period of the timbal muscle contractions correlated with changes in sound pulse amplitude during singing.
Keywords: Cicadas, sound production, calling song, EMG recording, amplitude modulation.
S. Parsons (1996). A comparison of the performance of broad-band and narrow-band bat detectors in 2 different habitat types. Bioacoustics 7(1): 33-43
Abstract
The use of bat detectors to monitor bat activity is common. Although several papers have compared the performance of different brands, none have dealt with the effect of different habitats nor have they compared narrow- and broad-band detectors. In this study the performance of four brands of ultrasonic bat detector, including three narrow- band and one broad-band model, were compared for their ability to detect a 40 kHz continuous sound of variable amplitude along 100 metre transects. Transects were laid out in two contrasting bat habitat types: grassland and forest. Results showed that the different brands of detector differed in their ability to detect the source in terms of maximum and minimum detectable distance of the source. The rate of sound degradation with distance as measured by each brand was also different. Significant differences were also found in the performance of different brands in open grassland versus deep forest. No significant differences were found within any brand of detector. Though not as sensitive as narrow-band detectors, broad-band models hold an advantage in their ability to identify species where several species are found symmetrically.
Keywords: bat detector, habitat, comparison, ultrasound, transmission
A.G. Daws, H.C. Bennet-Clark & N.H. Fletcher (1996). The mechanism of tuning of the mole cricket singing burrow. Bioacoustics 7(2): 81-117
Abstract
1. Experimental and theoretical studies on the acoustics of the singing burrow of the mole cricket Gryllotalpa australis are reported.
2. The burrow typically consists of a bulb about 26 mm long and 20 mm in diameter, connected through a constriction of diameter about 10 mm to a flaring horn with length about 40 mm and equivalent mouth diameter about 34 mm. The mouth geometry of the burrow differs from one species to another, and the aperture may be either single, double or even multiple. The end of the bulb opposite the horn connects to a narrow exit tunnel of diameter about 8 mm and length up to 1 m. The singing cricket positions itself close to the constriction between the bulb and the horn and produces a song with a frequency around 2.5 kHz.
3. Measurements of sound pressure within the burrow when it is excited by an external sound source at the song frequency show a pressure minimum at the constriction and an amplitude and phase distribution that is consistent with resonance of the burrow at its second modal frequency. The burrow is approximately three-quarters of a wavelength long at this frequency. The same result is obtained when the burrow is excited by a dipole source located near the constriction.
4. Non-parametric model calculations confirm this conclusion and also give broad agreement with the measured response curves over a frequency range from about 1.5 to 5 kHz. The calculated curves indicate an additional resonance at about 1.2 kHz associated with the first mode of the burrow - the Helmholtz or Klipsch resonance - which is apparently not utilized by the insect. This detail is consistent with earlier measurements, and is also supported by measured responses reported here that show an increase in sound pressure with decreasing frequency below 2 kHz as predicted by the model.
5. The measured performance of the burrow is broadly consistent with the model. According to the model, the burrow geometry is close to optimal for maximal sound power radiationKeywords: mole crickets, resonators, sound production, bio-acoustics, burrow, Gryllotalpa
A. Motis (1996) The whistled song of the European starling Sturnus vulgaris and the spotless starling Sturnus unicolor in North-east Spain. Bioacoustics 7(2): 119-141
Abstract
This paper describes the whistled songs of two allopatric populations of the European starling and spotless starling in NE Spain. The results show that European starlings in NE Spain sing the same whistled themes found earlier in other European populations and confirm the universal character of these themes. There are some differences between European starlings from NE Spain and other populations: rising phases appear for Inflection theme high-form, Inflection theme and Simple theme, and also differences of rate of emission appear for others (Rhythmic theme). Harmonic theme has not been found. Likewise, the first analysis of the spotless starling's whistled song shows that it shares the same general whistled song structure with the European starling; whistles have similar structural parameters (modulation, duration, frequency) and can be classified in the same categories or themes; a new theme appears, the Trilled theme, which has not been found to date in the European starling. Dialectal areas have been found in both species for the same themes (Inflection theme, Simple theme). The males of both studied populations have larger repertoires in comparison to other studied populations of the European starling.
Keywords: European starling, spotless starling, whistled song, parametric species, Spain
A.G. Daws, R.M. Henning & D. Young (1997). Phonotaxis in the cicadas Cystosoma saundersii and Cyclochila australasiae. Bioacoustics 7(3): 173-188
Abstract
1. Phonotaxis was investigated in two cicada species: Cystosoma saundersii and Cyclochila australasiae. Females were placed on a stick within a flight cage and presented with artificially generated calling songs. These model calling songs had a range of carrier frequencies, but their temporal parameters were similar to those of the natural calling song. They were broadcast at intensities 30 to 40 dB above the physiological threshold for each frequency.
2. Phonotaxis of female Cystosoma saundersii was restricted to a 45 minute period just after sunset, and was highly directional. Between 60 and 70% of flights made during trials in which a model calling song was broadcast were directed towards the loudspeaker at both frequencies tested.
3. Phonotaxis of female Cyclochila australasiae occurred throughout the evening, and showed no directional preference toward the loudspeaker. The mean number of flights per trial period was significantly greater in trials during which a model calling song was broadcast than in control trials during which no model calling song was broadcast. There was no significant difference in the mean number of flights per trial with different carrier frequencies.
4. In female cicadas, acoustic signals of the males are preferentially graded by the tuned auditory system; phonotactic decisions are then made on the basis of relative intensity without active discrimination between frequencies.Keywords: Acoustic communication, cicada, phonotaxis, frequency selectivity, auditory threshold
N. Vaughan, G. Jones & S. Harris (1997). Identification of British bat species by multivariate analysis of echolocation call parameters. Bioacoustics 7(3): 189-207
Abstract
1. A method for the identification of bat species from time-expanded broad-band recordings of their echolocation calls is presented. The method may be used for the assessment of habitat use by bats.
2. Recordings were made of echolocation calls produced by 536 bats of known species identity, belonging to 15 species found in Great Britain. One call was analysed per individual, and sonograms and descriptive statistics of six time and frequency variables of calls are presented. British bats can be placed in three groups according to the structure of their calls: high duty cycle FM/CF/FM bats (Rhinolophus spp.), low duty cycle FM bats (Myotis spp. and Plecotus spp.) and intermediate duty cycle FM/CF bats (Pipistrellus and Nyctalus spp. and Eptesicus serotinus).
3. FWCF/FM bats could be identified from the peak frequency of their calls. Two separate quadratic multivariate discriminant analyses were carried out on the time and frequency parameters of calls produced by FM bats and FM/CF bats. For FM bats 67%, and for FM/CF bats 89%, of unknown calls were classified to species.Keywords: Chiroptera, discriminant analysis, sonographic analysis, spectrograms, ultrasound
H. Khanna, S.L.L. Gaunt & D.A. McCallum (1997). Digital spectrographic cross-correlation: tests of sensitivity. Bioacoustics 7(3): 209-234
Abstract
Digital spectrographic cross-correlation (SPCC), a technique described by Clark et a1. (1987), simultaneously analyses frequency, amplitude and time components of a signal, and returns a single peak correlation coefficient. The procedure is objective and uses all the information in the spectrogram. As such, it is a candidate to replace and/or supplement visual spectrogram comparison and multivariate analysis as the technique of choice for comparing sounds. With the increasing availability of sound analysis software with built-in cross-correlation routines, the procedure is becoming readily available to biologists who may not have extensive knowledge of acoustics. This ease of access increases the potential for misapplication of the technique or misinterpretation of results. To assess the utility of SPCC and to highlight pitfalls that need to be avoided in its implementation, we performed a series of tests designed to reveal the sensitivity of the peak cross-correlation coefficient to a variety of parameters. In general, SPCC provides a good measure of the similarity between simple, continuous signals. However, there is no single best measure of similarity because of the complementarity of frequency and time resolution. More complex signal structures, such as those with overtones or complex vocalizations, will often return misleading coefficients. In all cases, pre-test preparation of signals is of critical importance.
Keywords: sound, digital analysis, spectrogram, cross-correlation, sensitivity test
L. Schrader & K. Hamerschmidt (1997). Computer-aided analysis of acoustic parameters in animal vocalizations. Bioacoustics 7(4): 247-265
Abstract
The computer-aided analysis of acoustic signals of mammals is still a problem, as often (a) sound structures are complex, (b) vocal repertoires often comprise an enormous variety of vocalisations, (c) recordings are influenced by the acoustic conditions of the environment, and (d) the distance and spatial orientation of the sender to the microphone changes. In recent software packages for the analysis of acoustic signals, procedures are integrated which allow the calculation of a variety of signal features. However, these algorithms are often problematic under the conditions mentioned above. In this paper, we present a multi-parametric approach which reduces these problems and which allows a quantitative and reproducible analysis of complex animal vocalisations. Our approach comprises the following aspects: (1) reduction of influences of recording conditions, (2) determination of different sound features and (3) calculation of parameters to characterize these sound features. All calculations are done on the basis of the digitized spectrograms. Special attention is given to the use of smoothing algorithms and dynamic thresholds in order to estimate sound features and to reduce influences resulting from recording conditions. The suitability of our approach has been demonstrated successfully for vocalisations of different species.
Keywords: computer sound analysis, multiparametric approach, vocalisations, mammals, primates
S. Haftorn (1997). A unique local call in the Willow Tit Parus montanus. Bioacoustics 7(4): 267-280
Abstract
A unique up-slurred call of the willow tit Parus montanus, rendered pui or plui, was discovered at a locality in the birch alpine region of central Norway in the summer of 1987 when three neighbouring pairs shared this call. Up to 1996 inclusive an additional number of 19 pui-calling individuals were found. Typically, these birds were either offspring of birds already uttering the call, or members of winter flocks in which the dominant adults possessed the call. The call is evidently acquired by learning and serves as an alternative alarm call. It is suggested that rudimentary pui-calls are a normal component in babbling series of young willow tits in general and that the development of these into full calls depends on appropriate tutors. It should be emphasized that the pui-call does not replace another call in the repertoire, but is an extra call adding to the repertoire. It is probably the first time that such a phenomenon has been reported in birds. The expectation that the call would spread in the population has so far proved wrong.
Keywords: Parus montanus, new call, vocal learning, call development.
D. Vankova & J. Malek (1997). Characteristics of the vocalisations of Red Deer Cervus elaphus hinds and calves. Bioacoustics 7(4): 281-289
Abstract
The voices of 8 hinds and their 7 offspring were analysed spectrographically. They were transformed into sonograms and the following parameters were measured: duration, fundamental frequency and frequency bands with high amplitudes. The animals emitted single calls or a series of sounds at irregular intervals. The single calls were monosyllabic and the series were homotypical sequences. The hind voices were deep and bleatlike, ranging in frequency from 70 to 3000 Hz. The fundamental frequency was 108.35 + 15.21 Hz and the duration was 0.27 + 0.14 sec. There were 1 to 8 frequency bands with high amplitudes created. Differences between individual voices were found in all characteristics of vocalization tested. The variation between voices was a result of the combination of these characteristics. The most important factor seemed to be the pattern of main frequency bands with high amplitudes. The calf voices were high, whiny and tonal, ranging in frequency from 320 to 7000 Hz. The fundamental frequency was 736.97 + 177.67 Hz and the duration was 0.26 + 0.12 sec. They were similar to each other, and inter-individual variation was not very apparent. This suggests that while hinds can be recognized individually by voice, it is probably not possible to distinguish the calves by voice alone. This is in accordance with parallel findings, that hinds did not seem to recognise their own calf’s voice.
Keywords: red deer, Cervus elaphus, vocalization, individual differences, sonograph, communication.
A. Michelson & K. Rohrseitz (1997). Sound localisation in a habitat: An analytical approach to quantifying the degradation of directional cues. Bioacoustics 7(4): 291-313
Abstract
Although much research has been done to describe the degradation of sound signals propagating in natural habitats, the directional cues of sound have so far been neglected. This paper describes a first approach to quantifying the degradation of directional cues in sound propagating parallel to the ground in a grassland habitat of orthopteran insects. A matched pair of probe microphones measured the sound amplitude and phase close to the ears of grasshopper carcasses for 12 evenly spaced directions of sound incidence. The degradation was found to increase with frequency and distance from the sound source and to decrease with distance from the ground. The acoustical data were used to predict how well animals with different auditory systems can determine the direction of the sender. At one position in the habitat, the predictions were compared with the pattern of phonotactic responses of live grasshoppers. Amplitude cues appear to degrade much faster with distance than phase cues. Animals exploiting phase cues may therefore maintain a reasonable directional hearing when the amplitude cues no longer make sense. The pressure-difference-receiver type of ears responds to phase differences, and these ears may be particularly suited to overcoming the degradation of directional cues. This suggests that the possession of such ears may be an adaptation not only to small body size (relative to wavelength), but also to the acoustic properties of the habitat.
Keywords: sound, localization, degradation, directional hearing, grasshopper, pressure difference receiver