In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 53, No. 1_Supplement ( 1973-01-01), p. 291-292
Abstract:
Investigators have suggested several internal noises that affect absolute thresholds (e.g., heart sounds, circulatory pulsations, muscle tremors). Furthermore, it has been suggested that blood flow may modulate aural noise in the external canal. Since mental blood vessels cannot expand outward due to bone encasing the canal, an inward expansion is suggested which induces an increase in aural noise by decreasing mental volume under the earphone. In short, the meatal pulsation hypothesis (MPH) suggests a modulation of aural noise as a function of blood flow through the ear canal. This study examines the MPH under three conditions (tight and normal fitting supraaural cushions and an insert earmold) as a function of the cardiac cycle. Three dependent measures were obtained, viz., EKG, blood flow at the earlobe, and pressure changes within the ear canal (positive pressure indicating, according to the MPH, an inward expansion of the blood vessels). The EKG R-wave keyed a signal averaging computer which in turn averaged the data over 32 separate heartbeats. Results indicate: (1) a maximum positive pressure approximately 225–250 msec after the R-wave with rapid decreases prior to and immediately after the maximum (tight fitting earphones); (2) no systematic pressure change with normally fitting earphones; (3) an inverse relationship between blood flow at the earlobe and pressure change within the meatus. The maximum negative pressure occurring near 225–250 msec after the R-wave.
Type of Medium:
Online Resource
ISSN:
0001-4966
,
1520-8524
Language:
English
Publisher:
Acoustical Society of America (ASA)
Publication Date:
1973
detail.hit.zdb_id:
1461063-2
