"Hollers out" is an idiom that refers to shouting or speaking out loudly. The antonyms for this phrase can be expressed in various ways, such as speaking softly, whispering, mumbling, muttering, or murmuring. When someone speaks softly, they are using a low volume of voice, and there is a gentle quality to the sound. Whispering has an additional element of secrecy or confidentiality, while mumbling or muttering can imply a lack of clarity or conviction in the speaker's words. Lastly, murmuring has a calming and soothing effect and is often used to convey comfort or reassurance. Overall, there are many ways to communicate without hollering out, and each has its own unique connotations and contexts.