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Fetal acoustic stimulation test: stimulus features of three artificial larynges recorded in sheep
R M Abrams1, K J Gerhardt, C Rosa
1Department of Obstetrics and Gynecology, University of Florida College of Medicine, Gainesville 32610-0294, USA.
Objective:
The purpose of the current study was to evaluate the characteristics of vibroacoustic devices used for fetal stimulation.
Study Design:
Intrauterine sound pressure levels over a frequency range of 40 to 5000 Hz were measured with hydrophones in anesthetized sheep. Stimulators included the AT&T (Martinsburg, W.V.) and Servox (Hearing Instruments, Piscataway, N.J.) artificial larynges, the Corometrics fetal acoustic stimulator (Wallingford, Conn.) and electric toothbrush.
Results:
Intrauterine spectral patterns resulting from stimulation with the AT&T, Servox, and Corometrics devices were characterized by numerous high-level overtones above a fundamental frequency between 97 and 163 Hz. Fundamental frequencies recorded during toothbrush stimulation were 22 to 24 Hz with reduced but identifiable overtones up to 250 Hz.
Conclusions:
Fetal vibroacoustic stimulators that operate on the principle of the electronic artificial larynx produce very similar intrauterine sound pressure levels.