Have you ever noticed how most kids have a voice pitch of "loud" and "louder?" Why is it that kids, especially toddlers, seem to equate loudness with getting heard? Do they have some sort of misguided belief that if they speak in a normal tone then nobody will listen? A quick listen in any setting that involves kids (some grownups never seem to learn this volume control either), will send your poor, sensitive ears in overdrive. Kids often shriek, stomp, and well, "talk" is screechy tones that border on shouts ... and sometimes do so from the moment they rise until they fall fast asleep. No wonder we adults become tone-deaf!
If your kids fall victim to "loud, louder, loudest" talking, it's time to turn down the volume and actually teach the art of what is often aptly named "the inside voice." Make it a game, it that type of approach works best with your child's age and development. Or practice the tried-and-true advice child experts also recommend when administering discipline: when trying to calm or "ssshhh" your child, speak calmly, quietly, and with a soft demeanor. If a kid isn't quiet and attentive, he will be unable to hear what you say. If your child is escalating with noise or seems to be spiraling out of control, calm him down by being calm and quiet yourself.
Frequently repeat that you are using your inside voice (assuming you are indoors), and that this is the appropriate speech volume and tone to use at any time when you are in a house, building of any kind, or any facility. You can also tell kids that they can use their "outside voices" (within reason) when they're outdoors, on the playground, or other "hoot and holler" appropriate times.
To help reinforce differences, praise kids for their appropriate indoor voices, offer incentives like taking them to the local library when they have achieved voice control, and then surprise them with a visit to a park or outdoor walk and be the first to let out some playful "hoots" of your own!