In the Messages app on your iPhone, there are two different microphone icons, and each serves a distinct purpose.

The first and second images show the Audio Message microphone icon remaining active in the Messages app even after an audio message has been successfully sent.
This is expected behaviour and does not mean that the iPhone is still recording your voice. The Messages app may retain the Audio Message interface based on your recent activity.
As illustrated in the images, deleting the sent audio message will not necessarily make the microphone icon disappear immediately. The icon may continue to appear even if you close the Messages app and reopen the conversation.
However, when you begin composing a regular text message (not an audio message), the interface changes. As shown in the third and fourth images, the Audio Message microphone icon is replaced by the Dictation microphone icon, which is associated with the text-entry field.
This demonstrates the distinction between the two microphone controls:
- Audio Message microphone: Used to record and send voice messages. Its appearance may persist after sending an audio message.
- Dictation microphone: Used to convert your speech into text while composing a regular text message.
Therefore, the persistent Audio Message icon should not be interpreted as an indication of an ongoing recording. It is simply part of the Messages app's current interface state. The microphone control changes according to the type of message you are composing.
Important: The Dictation microphone and the Audio Message microphone are two entirely different features. Dictation converts speech into text, whereas Audio Message records and sends your voice as an audio clip. Their appearance and behaviour should not be confused with each other.