After developing and experimenting with the phonetic typewriter, which is a noise-gated stream of user-supplied speech-like sound, I noticed that at times, it seemed like there was a mix of the expected audio and something else. This gave me reason to believe that there could be voices directly from the noise itself.

Direct voice, as it were, corresponds to extracting the voices from the noise with no extra audio added in. This method is indeed the original method of spirit communication / listening from ITC/EVP pioneers Jurgenson and Raudive. Purists believe it is only the method, feeling that having user-supplied speech is a form of "cheating." However, as we learned earlier, as long as we know what the supplied audio was, we can determine if changes were made, or if certain phonemes were emphasized/amplified.

Traditionally, direct voice can be a slow, arduous method. Start a tape recorder, ask a few questions, and wait for an answer of a few words to show up on the tape medium. Do this enough and collect samples of occasionally legible spoken words.

My colleague, Keith Clark and others, have realized that there may be a lot more, almost continuous stream of anomalous speech in the noise if one utilizes post-processing denoising techniques on a hardware noise source (e.g., radio static). In fact, these processing techniques, through the form of various combinations of audio plugins, can be applied in real-time to the noise produce speech-like sounds.

Where my research evolved in the direct voice arena was a systematic exploration of four software techniques for extracting a weak voice signal from an otherwise dominant noise source. I looked at spectral subtraction, musical vocoder, formant detection/synthesis and machine learning.

In future articles, I will explain each method in more detail.