Reference for Taanit 27:12

תנאי היא דתניא על אלו מתריעין בשבת על עיר שהקיפוה גייס או נהר ועל ספינה המטורפת בים ר' יוסי אמר לעזרה אבל לא לצעקה

Now at Jericho the shofar [was used to give the alarm]. This would be a refutation of him who said: By 'anenu [only]! Hence [we must conclude] that all are agreed that the sounding of the shofar constitutes the sounding of an alarm, and that they differ only with regard to [the recital of] the 'anenu; one takes the view that it constitutes the sounding of an alarm, and the other that it does not.

Jastrow