While it is primarily designed for real-time communication, you can also use it to process pre-recorded audio files.
Audacity: Audacity is a free, open-source audio editing software that offers a range of features for manipulating audio recordings. It includes tools for noise reduction and amplifying specific sections of a recording. It is available for Windows, Mac, and Linux.
Adobe Audition: Adobe Audition is a professional-grade audio editing software that provides advanced noise reduction and voice enhancement capabilities. It offers precise control over audio editing and can be used to clean up background noise and enhance voice recordings. However, it is a paid software.
RX by iZotope: RX is a powerful audio repair and restoration software that includes a range of features for noise reduction, voice isolation, and audio enhancement. It is widely used in professional audio production and post-production workflows.
These are just a few examples of apps that can help reduce background noise and amplify voices in voice recordings. Depending on your specific needs and platform (mobile or desktop), you can explore these options or search for alternatives that suit your requirements.