Unraveling the fluid mechanical mechanisms of sound production in pulsatile tinnitus using high-fidelity CFD.

Venous pulsatile tinnitus (PT) is sound associated with abnormal blood flow near auditory structures in the head, which can impact mental health and may be associated with intracranial hypertension. High-frequency flow instabilities, vortical flow, and regions of high time-averaged wall shear stress (TAWSS) have previously been associated with the sounds of PT, but do not identify potential mechanisms for sound production. In this study, the spectral power index of the wall pressure ( SPI P ) was used to determine the locations where sound could be transmitted through the walls of cerebral venous sinuses. These locations were then analyzed using maximum dissipation maps, streamlines, spectrograms, and swirling strength to understand the underlying flow phenomena that induce sound production. The results show that regions of high SPI P do not correspond with high TAWSS, vortical flow, or regions of highest dissipation. Rather, they appear to occur beyond regions of high dissipation where part of the post-stenotic flow splits off and interacts with obstructions, forming larger structures that beat against the wall, in addition to smaller flow structures. It is proposed that these structures are capable of producing the intermittency in pressure required to create sound that may be able to transmit to the ear.