The source of the "Kraa. Kraandl" sound heard near the end of the Sirens overture is identified several sentences from the chapter's end: "Tram kran kran kran. Good oppor. Coming. Krandlkrankran." Bloom sees, and hears, a tram moving up the northern quays in the direction of Phoenix Park, and he spots a good opportunity to release some intestinal gas without being noticed.

John Hunt 2023

1907 photograph of a tram moving downriver on Bridge Street, across the river and several blocks upstream of Bloom's position on the northern quays just past the end of the large Four Courts building. Source: