An 'indoor voice' is speaking not too quietly or not too loudly, so that people close to us can hear us comfortably.
Usually we don't need to speak loudly when we are indoors. We can use our normal talking voice. This means that the people we are speaking to can hear us but other people are not disturbed. If it is really quiet in the room we usually need to talk a little quieter too.
Talking too loudly or shouting indoors can make other people upset. Adults may get cross with us if we talk too loudly.
It is usually OK to talk loudly or shout when outside on the playground. It is usually not OK to talk loudly or shout when indoors.
My Indoor Voice
My indoor voice is the voice I use for speaking when I am inside.
When I am indoors it is important that I try not to speak too loudly. Talking too loudly can distract and annoy other people. If I talk too loudly I may make adults cross with me.
When I am indoors I can use a normal talking voice. This is not too loud and not too quiet. The right volume for my indoor voice can change depending on where I am, who I am with and what other sounds can be heard.
I can try and use my indoor voice when ever I am inside. This is my normal voice for speaking. It is not too loud and not too quiet. It is just right for the place and time when I want to talk.