Why did the Prophet, peace and blessings be upon him, not object to women raising their voices in his presence before Umar's seeking permission?

The women who were with the Prophet, peace and blessings be upon him, were the Mothers of the Believers and perhaps others. Umar advised them out of respect for the Prophet, peace and blessings be upon him. Some scholars have mentioned that their raising of voices was not prohibited, but rather due to overlapping voices or excessive talking and requesting expenses. This might have been before the prohibition of raising one's voice above that of the Prophet, peace and blessings be upon him. There is no evidence in the hadith (definition) that their raising of voices was above the Prophet's voice; rather, they would raise their voices contrary to their usual custom, relying on his good character.