This app allows you to convert an image to audio file, and Decode, Play a audio file via spectrogram.
You can make a sound image that is viewable on a spectrogram. With this app you can convert your images to audio and secretly send them to others. In order to convert an image, you just need to select an image from your computer, Google Drive, Webcam, and Clipboard.

This app provides a standard spectrogram audio player. You can also play multiple audio/video file (mp3, m4a, mp4...) with a spectrogram. 
Supported formats: jpg, jpeg, png, gif, bmp, webp, mp3, m4a, ogg, mp4, webm...

A spectrogram is a visual representation of the spectrum of frequencies of sound or other signal as they vary with time. Spectrograms are sometimes called sonographs, voiceprints, or voicegrams.