If you have either iOS 11 or later, or even an iPadOS, you can create a screen recording and thus, capture sound on your iPhone, iPad, or iPod touch. Here is a guide on how to do so.
Recording the screen on your iPhone, iPad, or iPod touch
If you have iOS 14 or later, go to Settings > Control Center and tap on More Controls, and then on the Add button, which looks like . It can be found next to Screen Recording. If you have an iOS 13 or earlier, tap on Customize Controls instead of More Controls.
Open Control Center on your device.
Touch and hold on to the grey Record button , and then tap on Microphone.
Tap on the Start Recording option, and then wait for the countdown of three second.
Open Control Center on your device, after which you have to tap the red Record button. This button will look like this . Another option is to tap on the red status bar at the top of your screen and press Stop.
However, you might also want to record some audio along with the video, for which you will have to turn the in-built microphone on.
Prior to starting the recording, press and hold on to the screen record button. Tap on the microphone button on the pop-up screen to turn on the microphone. Following this, tap on the “Start Recording” option. The countdown will start in this window. Touch any place on the screen to exit the screen, and then press the next screen to close the Control Center.
You should keep in mind that after you turn the microphone on, it will stay on the next time you record your screen by default unless you manually go back in and turn it off.
The video will automatically be stored with the rest of your photos and videos in your Photos mobile application.