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Results for “Echolocation”

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At least 307 records · Page 17Linked to original sources
PubMed1991

The emission pattern of vocalizations and directionality of the sonar system in the echolocating bat, Pteronotus parnelli.

The radiation patterns of the first three harmonics (approx. 30, 60, 90 kHz) of the mustached bat biosonar signal were measured from vocalizations elicited by cortical microstimulation. The primary foci of the acoustic beam patterns were in front of the mouth but somewhat below the horizontal plane. The prominent second and third harmonics showed sharp cutoffs between 20 degrees and 30 degrees lateral to the midline. Sidelobes were found, suggesting the influence of some vocal tract interference. When compared with previously measured estimates of the directionality of the auditory system, the vocal emission patterns are roughly complementary: Regions of maximum auditory sensitivity are found in areas of submaximal power for the sonar pulse beam pattern. The result is that, for the two most important harmonics, the "biosonar system" (i.e., vocal beam pattern plus receiver directionality) has a broader and more uniform directionality than either component alone. Therefore, within a limited region of space, echo amplitude will vary less as a function of angular displacement. This reduces the confounding influences of absolute sound pressure level on interaural intensity differences.

Animals↗
PubMed1966

Optomotor responses by echolocating bats.

Optomotor responses to moving stripes have been elicited from nine species of Microchiroptera. The minimum separable visual angle of two phyllostomids, under the experimental conditions, probably lies between 3.0 and 0.7 degrees; that of Myotis lucifugus, between 6.0 and 3.0 degrees. Four species indicate an ability to resolve stripes subtending 0.7 degree, the narrowest tested.

Animals↗
PubMed1996

The peripheral auditory characteristics of noctuid moths: responses to the search-phase echolocation calls of bats

The noctuid moths Agrotis segetum and Noctua pronuba show peak auditory sensitivity between 15 and 25 kHz, and a maximum sensitivity of 35 dB SPL. A. segetum shows a temporal integration time of 69 ms. It is predicted that bats using high-frequency and short-duration calls will be acoustically less apparent to these moths. Short-duration frequency-modulated (FM) calls of Plecotus auritus are not significantly less acoustically apparent than those of other FM bats with slightly longer call durations, based on their combined frequency and temporal structure alone. Long-duration, high-frequency, constant-frequency (CF) calls of Rhinolophus hipposideros at 113 kHz are significantly less apparent than those of the FM bats tested. The predicted low call apparency of the 83 kHz CF calls of R. ferrumequinum appears to be counteracted by their long duration. It is proposed that two separate mechanisms are exploited by bats to reduce their call apparency, low intensity in FM bats and high frequency in CF bats. Within the FM bats tested, shorter-duration calls do not significantly reduce the apparency of the call at the peripheral level, though they may limit the amount of information available to the central nervous system.

Journal Article↗
PubMed1975

[Certain problems of study of cardiohemodynamics by the method of ultrasonic Doppler-echolocation].

Results obtained in experiments on 10 adult mongrel dogs are offered. A synchronous registration of ultrasonic doppler-cardiograms (USDC) and of the intraventricular pressure continued throughout the experiment helped establish the relation between the pressure range in the left ventricle and the acceleration on the USDC curve. On the ground of the dependence thus obtained 2 indexes are proposed, viz. for an indirect evaluation of the intraventricular pressure (the index of "rated acceleration") and for appraising the contractability or the muyo cardium (the index of "relaxation from acceleration"). The available data might in the future provide for the possibility of devising appliances supplementing and replacing the catheterization.

Animals↗
PubMedDate not supplied

[Method of unidimensional echolocation of the cerebral aqueduct and upper portions of the 4th ventricle in healthy subjects and in pathology].

The authors suggest a method of unichamber echo location of the aqueduct and upper parts of the fourth ventricle by means of which it is possible to determine displacement of these parts of the c.s.f. system in a plane close to the frontal plane in development of a volumetric focus in the posterior cranial fossa. The value of the method in making the diagnosis of a surgical pathological condition in the posterior cranial fossa is almost the same as the value of unichamber echo diagnosis of supratentorial processes.

Arachnoiditis↗