Reducing the number of separate measurements of an audio file is called?

Reducing the number of separate measurements of an audio file is called "data compression." This process involves encoding the audio data in a way that maintains its quality while requiring less storage space. Compression can be either lossless, preserving all original data, or lossy, where some data is discarded to achieve smaller file sizes. Techniques like MP3 or AAC encoding are common examples of lossy audio compression.