Plethysmography as an objective method of audiometry

Area of Science:

• Audiology
• Cardiovascular Physiology
• Psychoacoustics

Background:

• Understanding the physiological responses to auditory stimuli is crucial.
• Vasomotor reactions, indicative of autonomic nervous system activity, can be influenced by various sensory inputs.
• Previous research has explored sound's impact on physiological parameters, but specific plethysmographic responses to pure tones require further elucidation.

Purpose of the Study:

• To investigate the subjective and objective vasomotor reactions to pure tones of varying frequencies and intensities in healthy individuals.
• To determine if these sound-evoked plethysmographic reactions are persistent under audiometric conditions.

Main Methods:

• Thirty-seven subjects with normal hearing and cardiovascular function participated.
• Subjects were exposed to pure sounds at 1024, 2048, and 4096 Hz frequencies.
• Sound intensities ranged from 0 to 80 dB above the determined hearing threshold.
• Plethysmographic recordings were used to measure vasomotor reactions subjectively.

Main Results:

• All subjects exhibited plethysmographic reactions in response to pure sounds.
• These sound-induced vasomotor reactions remained consistent and did not extinguish during the audiometric investigation.
• Responses were observed across all tested frequencies and intensities.

Conclusions:

• Pure auditory stimuli reliably elicit measurable vasomotor (plethysmographic) reactions in individuals with normal physiological parameters.
• The autonomic nervous system's response to sound, as reflected by vasomotor activity, is robust and not easily habituated during hearing assessments.