There are times when we are recording an audio or video file, we think that a portion of that recorded clip is not necessary. That is the time where the editing app enters. We cannot deny the fact that editing is essential now, especially when we want to make our recorded audio or video more appealing.
To cut audio on an iPhone, what you need is iMovie app. Here are the detailed steps.
Step 1. Open the iMovie app and click the Create Project that you want to edit then click the Movie on the options that will appear.

Step 2: After you added a file, click the clip to enable it. After that it will show the editing features.

Step 3: After the editing features showed on the lower part of the screen, press the Scissor icon then tap the Detach and a blue colored clip will appear, click the delete key then click the Done to make the changes permanent.

How to trim audio in iMovie on Mac?
Step 1. Upload your audio file on iMovie's timeline. After that, put the play head on the exact region of the frame that you want to trim.

Step 2: Once you have moved the play head on the region of frame that you want to cut, right click your mouse then click the Trim to Playhead on the options that will appear.

Step 3: After following the steps above, click the Save icon on the right upper part of the tool's main interface.
For more detailed guide, please refer to https://www.vidmore.com/edit-audio/cut-audio-in-imovie/.

If you are do not like using iMovie to trim your audio file, you can also try its alternative Vidmore Video Converter (https://www.vidmore.com/video-converter/), it can be used on both Windows and Mac computer.