Will the other party know when listening to imessage's voice?

The other party will know and will show that it has been read.

Make sure it's an Apple phone, and then open iMessage. If the SMS read receipt is opened, the read status will be displayed. ?

IMessage is an instant messaging software launched by Apple, which can send short messages, videos and so on. It has high security. IMessage is different from SMS/MMS service of operators. Users only need the data support of WiFi or 3G network to complete communication. IMessage uses the new message reminder system of iOS and Mac os, which can directly push information to the other party's screen, regardless of whether the other party is in the game or locked. If both parties are using iMessage, you can even see the state of each other's speech.