Rosh Hashana 3:2

All shofars are fit for fulling the mitzvah on Rosh Hashana except for that of a cow, which is called a “horn” (rather than a shofar). Rabbi Yosi pointed out that all shofars are called horns, as we see from Joshua 6:5, which refers to “a long blast from the ram’s horn.”

Rosh Hashana 3:3

The shofar used (in the Temple) on Rosh Hashana comes from an ibex and is straight. Its mouth is coated in gold and there are two trumpets, one on either side. The shofar blasts are long and the trumpet blasts are short because the mitzvah of the day is performed with a shofar.