On Erev Yom Kippur it is said that "we will be as pure as the angels and cleansed of our sins." There is one actual way we manifest that, and I think you will appreciate it.
No one among us is unfamiliar with the Shema and its refrain Barukh shem kevod malkhuto leolam vaed, "Praised be His glorious sovereignty throughout time." All year the prayer leader and the congregation read these auspicious words silently.
Yom Kippur is the only day of the year the refrain is recited aloud during the Shema. There are a litany of reasons for this. The emphasis given Barukh Shem... is a means of reliving and recalling the atonement rites conducted in the Temple. Also, at Jacob's deathbed his children affirmed their loyalty to God by proclaiming the Shema (Israel in this context refers to Jacob). And, Jacob responded Barukh Shem...
Interestingly, our Sages taught in the Talmud Pesachim 56a and Deuteronomy Rabbah 2:36 that we should say these words as Jacob did. But, since they are not found in the Torah, we should say them silently. How do we get from "silent" to "aloud" at Yom Kippur? Tradition has it that Moses heard it recited by the angels, and he taught it to Israel. All year we recite it silently since we are sinful and unworthy of using an angelic formula, but on Yom Kippur, when we are cleansed of our sins and are "as pure as angels," we recite as the angels did-aloud.
G'mar Hatimah Tovah (May we all be sealed in the Book of Life)! [i]
Rabbi Jeffrey Abraham
[i] This blessing arises from the concept that on Rosh Hashanah God judges individuals, but that judgment is not finalized or "sealed" until Yom Kippur, and is consequently only recited during the Ten Days of Repentance.