At this level, the carotid bifurcates and gives rise to its internal branch. If one hears a bruit only in the base of the neck or equally along the course of the vessel, it is referred to as diffuse. Such a bruit is less specific for carotid disease. Duration of the bruit is another traditional component of the description. A bruit of longer duration is associated with more severe stenosis especially if it extends into diastole.
Venous hums can masquerade as continuous bruits.
Intensity of the bruit has in one study been shown to correlate with degree of stenosis. In practice, the intensity of the bruit is related to the sixth power of the velocity of the blood flow and is the major determinant of intensity. One important clinical aspect of the Philips equation is that intensity is loudest with the bell distal to the site of the obstruction and directly facing the vessel. Orbital auscultation is a useful adjunct to the method described above. This technique involves gently placing the bell of the stethoscope on the orbit, lid closed, while the other eye remains open to reduce blinking sounds.