1)
Why did Moshe say "va'Yishma Hashem" - which is the Name of Rachamim?
1.
Oznayim la'Torah: He quickly 'jumped' and swore by the Name Hashem, before Elokim - the Name of Midas ha'Din - could place upon them a heavier punishment.
2)
What was the "Kol Divreichem" that Hashem rook note of?
1.
Seforno: It was the 'Bechiyah shel Chinam' (the baseless weeping) of which they were guilty on that fateful Tish'ah be'Av night. 1
2.
Oznayim la'Torah: "Kol represents the Lashon ha'Ra which they spoke about Eretz Yisrael, 2 and on account of which Hashem issued the decree that they would die in the desert.