It’s not necessary to convert MP3 audio to the better MP4 format for PowerPoint but, if you want to, there are various ways to do it.
MPEG-4 audio (.mp4 .m4a ) is recommended by Microsoft for PowerPoint 2016 (Windows and Mac), PowerPoint 2013 and Powerpoint for mobile devices. MP4 audio gives you better sound and, usually, more compact file sizes than MP3.
We regularly convert MP3 audio to MP4 for our portable music collection, see below for more info.
Online Converters
For occasional or one-off conversions there are various online services available. Upload your MP3, it’ll be converted for you and download an equivalent MP4.
http://www.zamzar.com/convert/mp3-to-mp4/
https://mp3toolbox.net/mp3_to_mp4
http://online-audio-converter.com/
iTunes
If you have iTunes on your computer, it has a good converter to MP4 included.
iTunes is free from Apple. Unless you do a lot of conversions, having iTunes might not be worth the trouble. It’s a 250MB download and fairly intrusive with links into other software, sluggish performance, regular updates and prompts to buy other Apple services.
Installing iTunes just to convert audio files is like installing a full-featured kitchen to occasionally boil water.
Advanced users could install iTunes (for occasional use) on a virtual machine (Hyper/V or VMware) to keep it contained from your standard software setup.
iTunes convert to MP4 M4A
To convert, first check the conversion settings. This tells iTunes the type and quality of file to make. Preferences | General | Import Settings. The settings might seem to only apply to importing audio but they’re also used for conversions.
Import Using: AAC Encoder is MP4 by another name
Setting: iTunes Plus is usually enough, but you can go to ‘High Quality’ or Custom.
Change the standard Songs view to show the Kind and Size columns.
To do the conversion, select the songs to convert then go to File | Convert | Create AAC version. Earlier iTunes had this option on the right-click menu.
Then wait a short time while iTunes does its thing. Both versions of the song should appear together in your list and you can compare file sizes.
Note: converting to MP4 does not always give a smaller file size. If the original MP3 has lower quality audio, the converted MP4 version can be larger or about the same.
To check the audio quality of any file, right-click then choose Get Info and the File tab.
You can delete the old MP3 version (keep a backup!) then move the new M4A version to wherever you need it for your PowerPoint presentation.
There are other MP4 converters available to download. Do a Google/Bing search and you’ll find many offerings.
Why else convert audio to MP4
For a long time we’ve used MP4 audio on portable devices like smartphones and tablets.
As you can see in the example above, the MP4/AAC version can about 15% smaller with roughly the same audio quality.
Across our entire portable music collection, conversion from MP3 to MP4 saves about 2GB of disk space. 2GB isn’t much on a normal Windows computer but it’s a noticeable part of a 32GB or 64GB smartphone.
Our strategy has two music collections:
The main Music collection of high-quality audio (MP3 @320kbs or lossless) with all the music. It’s the archival or complete collection.
A Portable Music collection. A selection from the main collection converted to MP4 for portable devices. These folders are kept on the main computer and automatically synchronized with portable devices using Resilio Sync.
Free ways to convert WAV and other formats to MP3 audio for PowerPoint
Grabbing audio only from online sources like YouTube
