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B Møhl

Publications and source records attributed to B Møhl.

14 recordsLinked to original sources
PubMed2002

Sperm whale sound production studied with ultrasound time/depth-recording tags.

Delphinoids (Delphinidae, Odontoceti) produce tonal sounds and clicks by forcing pressurized air past phonic lips in the nasal complex. It has been proposed that homologous, hypertrophied nasal structures in the deep-diving sperm whale (Physeter macrocephalus) (Physeteridae, Odontoceti) are dedicated to the production of clicks. However, air volumes in diving mammals are reduced with increasing ambient pressure, which seems likely to influence pneumatic sound production at depth. To study sperm whale sound production at depth, we attached ultrasound time/depth-recording tags to sperm whales by means of a pole and suction cup. We demonstrate that sperm whale click production in terms of output and frequency content is unaffected by hydrostatic reduction in available air volume down to less than 2% of the initial air volume in the nasal complex. We present evidence suggesting that the sound-generating mechanism has a bimodal function, allowing for the production of clicks suited for biosonar and clicks more suited for communication. Shared click features suggest that sound production in sperm whales is based on the same fundamental biomechanics as in smaller odontocetes and that the nasal complexes are therefore not only anatomically but also functionally homologous in generating the initial sound pulse.

Animals↗
PubMed2001

[Intersex: which gender should be chosen?].

A newborn infant with ambiguous genitalia is a medical emergency, and the choice of gender must take into account both the chromosomal and the gonadal sex, the hormonal milieu during fetal life, surgical aspects, the anatomy of the internal genitalia, as well as the prospects for future fertility, normal psychosexual development, and sexual function as an adult. Counselling requires paediatric endocrine, surgical, and psychological expertise, but the lack of knowledge of the long-term consequences of an intersex condition hampers rational treatment. It has long been customary to assign the child a female gender, whereas recent research points to a choice of a gender compatible with the chromosomal sex, if at all possible. This article reviews our knowledge in this field.

Counseling↗
PubMed2001

Sound transmission in the nose of the sperm whale Physeter catodon. A post mortem study.

During a sperm whale stranding at Rømø, the Wadden Sea, Denmark, on 4 December 1997, we were notified in time to start acoustic transmission measurements in the spermaceti complex 1 h after the specimen was seen alive. Frequency-modulated sound pulses, sweeping from 30 kHz to 10 kHz in 25 ms, were injected at the frontal surface at two positions: at the distal sac, and at the center of the junk (a compartmentalized structure below the spermaceti organ). A hydrophone next to the projector served as receiver. The analyses of the recordings show a repetitive, decaying reflection pattern at both projection sites, reminiscent of the multi-pulse click peculiar to sperm whales, although with minor differences in the duration of the intra-click intervals. This experimental evidence supports the Norris and Harvey (1972) theory of click generation in the spermaceti organ. Accordingly, the click is composed of a primary event, followed by a train of reflected pulses, spaced by the time required for the event to travel back and forth between air sacs (reflectors) at each end of the organ. The results also show that the junk readily transmits sound and probably is in acoustic contact with the spermaceti organ.

Animals↗
PubMed2000

Sperm whale clicks: directionality and source level revisited.

In sperm whales (Physeter catodon L. 1758) the nose is vastly hypertrophied, accounting for about one-third of the length or weight of an adult male. Norris and Harvey [in Animal Orientation and Navigation, NASA SP-262 (1972), pp. 397-417] ascribed a sound-generating function to this organ complex. A sound generator weighing upward of 10 tons and with a cross-section of 1 m is expected to generate high-intensity, directional sounds. This prediction from the Norris and Harvey theory is not supported by published data for sperm whale clicks (source levels of 180 dB re 1 microPa and little, if any, directionality). Either the theory is not borne out or the data is not representative for the capabilities of the sound-generating mechanism. To increase the amount of relevant data, a five-hydrophone array, suspended from three platforms separated by 1 km and linked by radio, was deployed at the slope of the continental shelf off Andenes, Norway, in the summers of 1997 and 1998. With this system, source levels up to 223 dB re 1 microPa peRMS were recorded. Also, source level differences of 35 dB for the same click at different directions were seen, which are interpreted as evidence for high directionality. This implicates sonar as a possible function of the clicks. Thus, previously published properties of sperm whale clicks underestimate the capabilities of the sound generator and therefore cannot falsify the Norris and Harvey theory.

Animal Communication↗
PubMed2000

Sperm whales (Physeter catodon L. 1758) do not react to sounds from detonators.

A number of observations show that sperm whales (Physeter catodon L. 1758) react to various man-made pulses with moderate source levels. The behavioral responses are described to vary from silence to fear. Click rates of five submerged male sperm whales were measured during the discharge of eight detonators off Andenes, northern Norway. In addition, the behavioral response of a surfaced specimen was observed. Click rates of the submerged whales and the behavior of the surfaced specimen did not change during the discharges with received sound levels of some 180 dB re 1 microPa peRMS. The apparent lack of response to the discharges could be due to similarity between sperm whale clicks and detonations. Accordingly, it can be speculated that the discharges may have been perceived as isolated clicks from conspecifics.

Animals↗
PubMed1999

Dolphin hearing: relative sensitivity as a function of point of application of a contact sound source in the jaw and head region.

The auditory input area of the dolphin head was investigated in an unrestrained animal trained to beach itself and to accept noninvasive electroencephalograph (EEG) electrodes for the recording of the auditory brain-stem response (ABR). The stimulus was a synthetic dolphin click, transmitted from a piezo-electric transducer and coupled to the skin via a small volume of water. The results conform with earlier experiments on acute preparations that show best auditory sensitivity at the middle of the lower jaw. Minimum latency was found at the rear of the lower jaw. A shaded receiver configuration for the dolphin ear is proposed.

Animals↗
PubMed1998

Bat sonar: an alternative interpretation of the 10-ns jitter result.

In 1990 Simmons et al. reported evidence of a time resolution hitherto unknown in any animal, namely a 10-ns jitter detection threshold in echolocating bats. This result is discussed. The calibration data from the original papers are examined. Observations indicating other cues than delay being presented to the bats are given. We offer an alternative explanation for the psychometric jitter function, based on the assumption of a subtle distortion due to impedance mismatch in the delay-producing apparatus. We also report that effects of impedance mismatch are detectable by a human subject in a model experiment.

Acoustic Stimulation↗
PubMed1992

Vaginismus--iatrogenic precipitation and maintenance.

Four cases of vaginismus are presented. Two of them illustrate an iatrogenic precipitation of vaginismus, one misdiagnosis of vaginismus, and one shows the use of unnecessary hymenectomy as the first choice of treatment of vaginismus. The etiology of vaginismus and the indications of first pelvic examinations are discussed.

Adolescent↗
PubMed1991

[Questions directed to the open-line telephone sex counseling service].

Inquiries to the open telephone-counselling service of the sexological clinic were registered from January 1st 1988 to January 1st 1990; a total of 168 calls, 29 of which were from professional therapists. The P-LI-SS-IT (Permission, Limited Information, Specific Suggestions, Intensive Therapy) model can be used to classify the calls, which fall within the first three categories of this model. Examples of these are given. The pattern and complaints in the inquiries are, by and large, identical with those in a Swedish sexological telephone-counselling. Contrary to a Dutch counselling service only a few telephonesex calls were registered. The use of resources is minimal and the capacity is estimated to fulfil the need. The inquiries correspond entirely to the original intentions of a telephone-counselling service.

Adult↗
PubMed1986

The detection of phantom targets in noise by serotine bats; negative evidence for the coherent receiver.

Using a target simulator three serotine bats, Eptesicus serotinus, were trained to judge whether a phantom target was present or absent. The echolocation sounds emitted by the bats during the detection were intercepted by a microphone, amplified and returned by a loudspeaker as an artificial echo, with a delay of 3.2 ms and a sound level determined by the overall gain and cry amplitude. The cry level of each pulse was measured and the echo level received by the bat was calculated. The target was presented in 50% of the trials and the gain adjusted using conventional up/down procedures. Under these conditions between 40 and 48 dB peSPL were required for 50% detection (Figs. 2, 3). In a subsequent experiment the phantom target was masked with white noise (No) with a spectrum level of -113 dB re. 1 Pa X Hz-1/2. The thresholds were increased by 7-14 dB. Energy density (S) of a single pulse was measured and used to estimate S/No, which ranged from 36-49 dB at threshold. Theoretically the coherent receiver model predicts the ratio between hits and false alarms observed for the bats at a S/No of ca. 1-2 dB. Since the bats require 40-50 dB higher S/No (Fig. 3), this is taken as negative evidence for coherent reception (cross correlation). Furthermore, a strong sensitivity to clutter was found since there seemed to exist a fixed relationship between thresholds and clutter level.

Animals↗