The idea
PCM WAV stores individual audio samples without lossy compression. Sample rate is the number of samples per second per channel, while bit depth controls the quantization of each sample. This tool exports 16-bit PCM, a common interchange format for audio editors.
Try it
A 10-second stereo file at 44,100 Hz and 16 bits needs 10 × 44,100 × 2 × 2 bytes, plus a 44-byte header: 1,764,044 bytes. Mono needs about half as much. Generate a metronome file and compare its duration and size with that formula.
What to watch for
The browser decodes uploaded audio at its AudioContext sample rate, often 44.1 or 48 kHz. A resampled WAV can differ from the original sample rate; the result page reports the actual output rate. More bytes do not guarantee more detail, and 16-bit export is not lossless relative to every possible source.
Next step
Check the downloaded file in an audio editor: duration, channels, sample rate and PCM format should match the result. Preserve the original if you need its original codec or metadata.