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There are two methods of ultrasound acquisition and analysis with PC's: The first and most straightforward solution is a special data acquisition board with a sampling frequency high enough to capture the entire bandwidth of the signals to be analysed. This requires taking the computer into the field if you have to do field research. The best choice would be a PCMCIA data acquisition card for portable notebook PC's. Unfortunately the devices available on the market still have limited sampling frequencies of approximately 100 kHz. This allows a usable bandwidth of less than 50kHz, which is not sufficient for all kinds of ultrasound. The data streams generated by these data acquisition boards can be stored on hard-disk and can then be read by the Avisoft-SONAGRAPH software using one of its user-defined import formats. The alternative method is the usage of a digital time-expansion bat- detector to transform the ultrasound into low frequency sound which can be processed by conventional audio equipment. These transformed sounds can be stored on standard tape recorders and can be transferred into the computer using a common sound-card. In this case the transformed ultrasound is treated like any other audio signal. In order to get the original scaling of waveforms, spectra and sonagram displays, the time-expansion factor used on the bat-detector can be specified in the Avisoft -SONAGRAPH software. Conventional bat-detectors using heterodyne or frequency division technology are not suited for spectral analysis on a computer. These devices could only be used to get an idea of the time structure of the signals.

In June 1995, a 12 days research cruise was organized in the Ligurian and North Tyrrhenian Sea to record cetacean sounds with the towed array of the University of Pavia. The cruise was supported by the Italian Navy within the ENCY 95 (European Nature Conservation Year) activities. The hydrophone was towed for 111 hours (out of 12 cruising days) at speeds up to 14 km/h; listening stations were held on a 24h schedule for at least 10 min every half an hour. One sperm whale was detected and located. It was heard at night and acoustically tracked for the following 8 hours. Within this period the whale was sighted at the surface 5 times, while 8 complete dives were continuously recorded on DAT tapes (about 6 hours of recording). The recordings are now archived at the Cetacean Sound Library held at the Centro. New methods of sound analysis were developed to make the analysis of such long recordings easier and to give compact pictures of whole dives. Our real-time analysis software was modified with new procedures able to 1) automatically detect and count clicks, 2) measure and save inter-click intervals, 3) save packed representations of the click sequences and display autocorrelograms to show the evolution of inter-click intervals over long periods of time. The analysis of the recordings shows that all the recorded dives were characterized by a typical and constant clicking pattern at their beginning. The duration of the acoustical emission, measured from the first click to the last click of each dive, was on average 27 minutes 30 seconds, while the silence related to the surfacing was on average 13 minutes and 11 seconds.

For one year, starting on September 5th 1994, the behaviour of a captive new-born bottlenose dolphin Tursiops truncatus and its mother was monitored through both video and acoustic recordings. The main objective of such research was to study the behavioural evolution of the two during the first year of the calf's life. Attention was focused on acoustic behaviour and its use in relation to the contexts. In order to be able to discover any possible correlation, the acoustic signals were analysed with a Pc-based DSP Workstation developed at the University of Pavia, and the resulting real-time spectrographic analyses were superimposed on the live video recordings.

Within the frame of European Nature Conservation Year 1995, the Italian Navy set up a cooperative research program with universities and other institutions to give logistic support and to apply its technologies to the study and protection of the marine environment. The project includes a research program on cetacean acoustics, mainly dealing with the sperm whale Physeter macrocephalus, to unveil and monitor its seasonal movements and behaviour. The Italian Navy surface vessels crews have been trained to visually recognize them in order to complete sighting schedules. Besides, personnel working on submarines and maritime patrol aircraft have been trained in identifying biological sounds recorded during ASW (Anti-submarine Warfare) operations. ASW techniques proved to be successful in finding and recording cetaceans. Unclassified sound recordings made independently by the Navy, with surface vessels, submarines and sonobuoys, have been provided to the Cetacean Sound Library of the Centro Interdisciplinare di Bioacustica e Ricerche Ambientali. The research continued in 1996 mainly with the collection of recordings from sonobuoys deployed while performing ASW patrolling activities. To date, several valuable recordings have been collected from elusive species like the sperm whale and pilot whale. Several recordings of sperm whale codas typical of the Mediterranean Sea (/// / pattern) have been collected, including new "short'' codas with the same distinctive pattern. Whenever possible, species identification of vocalizing animals was made by comparing sounds with those available in the Cetacean Sound Library.

The problems of reducing small cetacean bycatch in fishing nets are many and complex, and acoustic solutions need to be tailored to suit individual species and net types. Active deterrent devices or alarms have recently been shown to be beneficial in reducing the bycatch of harbour porpoises Phocoena phocoena in some carefully monitored trials in North American sink-gillnet fisheries (Kraus et al. 1995). The methodology employed to date is still at an early stage of development; typical devices generate simple 10 kHz tonal pulses from small battery powered packages distributed at intervals along the fishing net. The long term effectiveness of this approach has already been questioned, as small cetaceans are known to habituate quite quickly to novel stimuli. A more sophisticated approach, now at the trials stage, uses higher frequency, wideband signals which have been determined to be more aversive to this species (Goodson et a1. above). To minimise habituation effects over time, such 'beacon alarm' signals need only be transmitted occasionally if the acoustic activity of an approaching echolocating animal can also be detected and used to trigger the device into a transponder type of operation. Such a device has now been designed at Loughborough University and implemented using digital micro-controller technology. As this circuitry is programmable almost any complex waveform can be generated to suit specific applications. The use of a digital micro-controller permits a number of additional features to be implemented in software without a significant increase in the overall component count and, despite the sophistication, the cost per device remains acceptably low. It may be argued that a silent animal could remain at risk. However, in the context of bottom set nets (sink-gillnets) this should not apply, as the harbour porpoise swimming close to the bottom in deep water is there to forage for prey and hence actively employing its echolocation sense. This interactive approach reduces spurious acoustic emissions which waste battery energy and, as most responses are triggered by the approach of an animal at risk of colliding with the net, the deterrent effect is expected to be longer lasting. The alarm response ceases quickly once the animal turns away. Provided that these devices are spaced apart along the net within detection range of each other, additional benefit is obtained if they also respond to a neighbour's alarm signal as this will result in a 'ripple-fire' of activity along the net. This linking of emissions provides better orientation information than can be given by simple randomly timed pingers. lnteractive devices are also intended for application to large pelagic trawls, where the delineation of the net's boundary by such a ripple-fire transmission is expected to give a clearer indication of the extent of the hazard to an animal which may have followed fish into the net. Since triggering can also be stimulated by a ship's echosounder, these devices should make the location and recovery of lost nets a relatively simple exercise.

Field voles are common in Britain and across Europe where they may show regular fluctuations in population every 3-4 years. In some countries they are pests of agriculture and particularly of forestry. These voles are induced ovulators and, while their reproductive physiology is fairly well understood, little is known of their reproductive behaviour and especially of their acoustic communication. The present study has shown that in heterosexual encounters adult voles emit ultrasonic calls during a range of behaviours, as has been found in several other rodents. For example, male mice of different strains are known to emit 70 kHz ultrasonic vocalizations as part of their courtship behaviour, and rats emit 50 kHz pulses. In Microtus agrestis, the nature of the calls varies particularly in the amount of frequency modulation. The frequency ranges from 20 kHz to 80 kHz, with an average at 35-40 kHz, and the male seems to be the main emitter. In heterosexual encounters between sexually naïve animals both sexes call, but calling appears to be modified by sexual and parental experience, as sexually experienced males emit longer and wider calls than sexually naïve males, and sexually experienced females do not emit any ultrasonic pulses when presented with an anaesthetised male (also sexually experienced), as sexually naïve females do. The environment in which the animals meet also affects ultrasound emission: the calls emitted by pairs in the male's home cage were longer and of broader-bandwidth than those emitted in the home cage of the female. The effect, on the emission of ultrasonic pulses, of sexual and parental experience as well as the effect of different environments will be illustrated. The relationship between calls and the different types of behaviour and the effect of these calls on the recipients are currently being investigated.

During censuses of wolves, performed with the wolf howling technique, in the Foreste Casentinesi National Park, we recorded answers of wolf packs and isolated individuals. Most difficulties were caused by the distance between wolves and the recording equipment. The aim of this preliminary analysis was to verify if it was possible, in the wild, to distinguish by means of sonagraphic analysis: at adults from pups; b) the number of individuals of each pack; c) different adult individuals from each other. The first distinction is possible thanks to the different frequency range of adult and pup vocalisations. The substantial overlapping of different vocalisations makes the second aim difficult, but it is possible to determine a minimum number of individuals. The third aim is difficult to achieve because only few vocalisations of each individual can be collected.

The period immediately following birth appears to be particularly well suited to study the developmental similarities in vocal communication between man and other primates. Vocalisations performed by non-human primates during their first year of life are therefore particularly important in a comparative and evolutionary perspective, as they allow interesting comparisons with studies on human linguistic development. However, this topic has received little attention. We studied the functional relationships, in a social colony of pig-tailed macaques Macaca nemestrina, between the maternal response to the search for physical contact by the young and the physical structure of the vocalisations produced by the latter. The research was performed on three mother-young dyads, audio-recording the vocalisations produced by the young and by the adults and video-recording mother-young interactions. Our results provide a description of some of the physical characteristics of the vocalisations produced by the young during spontaneous interactions with their mothers; furthermore they suggest the existence of different structural or syntactical categories and suggest a relationship between maternal behaviour and vocalisation patterns.

A male, a female, two juveniles and two cubs of European otter Lutra lutra were filmed in a large enclosure during a period of 8 months. For each episode of acoustic communication, data were collected on uttered sounds, involved individuals, and their distance, postures and behaviour before, during and after vocalizing. Eight different sounds were considered, according to the inventory referred by Rogoschik (Wiss. Beitr. Univ. Halle, 37(1989): 213-221). Associations between the recorded parameters were evaluated by an association index. The male and female vocalized frequently towards the cubs and human beings, and cubs towards the female. Senders and addressees were found to be unequally distributed for the different sounds. Vocalizations occurred preferentially on land and along the banks. The most frequent behavioural contexts were parental contacts (between the female and the cubs), contacts with human beings and playing activity; on the other hand, vocalizations rarely occurred while fishing, moving, feeding and marking. Hiss and snort were uttered when an animal approached the addressee, from a distance of a few meters; they were often accompanied with a typical arcuated head movement. Moan was a threat sound, uttered while keeping the body motionless and fixing its eyes on the addressee. Chuckle, chuckle-chitter, chitter and squeal were mostly uttered at very short distances; although they all show a similar "staccato'' acoustic structure, only the chuckle was uttered in social contexts, while the other ones were associated with increasing aggressive excitement. Whistle was uttered usually in very long sequences, at long distances; its main function seems to be keeping an acoustic contact between individuals, in particular cubs and their mother; however, sometimes it was uttered by juveniles together with chitter and other agonistic sounds. This shows that the communicative system of the species is quite complex.