Steganography and “Silent Subliminals”

Steganography” from the Greek steganós (concealed) and graphia (writing), is the practice of hiding information within another message or physical object. It could be described as a form of “hiding in plain sight”.

There are several different stenanogrphic techniques relating to audio. This article, and the associated plug-in uses one specific technique called Amplitude Modulation (AM) encoding. This is the same process as is used by AM radio, except that rather than using radio waves to carry the audio, very high frequency audio is used instead.

AM Encoding is the most popular technique for creating “Silent Subliminal” recordings, which advocates claim can bring about positive shifts in one’s mindset. The technique was largely based on the 1989 US Patent US5159703A by Oliver M. Lowery for a “Silent subliminal presentation system”.

O. M. Lowery’s invention was based on the belief that speech messages that are AM encoded with a high audio frequency carrier, may be “decoded” by the listener’s subconscious mind, while remaining inaudible and indecipherable to the conscious mind. Despite the lack of empirical evidence to support his claims, the technique has become very popular in New-Age Wellness circles.


The author of this article and associate plug-in makes no claims whatsoever regarding the effectiveness or safety of “Silent Subliminals”.

The purpose of this article and the associated plug-in is to provide some background information about the steganographic technique of high frequency audio encoding of speech messages, and to provide an Audacity plug-in that allows experimentation with the technique.

How it works:

The idea is to hide a recorded speech message via AM encoding with a very high audio frequency carrier wave. This shifts the frequency range above 16 kHz which is largely inaudible to most adults. (People with very good high frequency hearing may still be able to detect a pulsating high frequency whistle, though it will be incomprehensible).

Sound Quality Limitations:

The format for audio CDs uses a sample rate of 44.1 kHz, which has an audio bandwidth up to approximately 20 kHz. This was considered to be the minimum requirement for very high quality audio. In order for the encoded message to be essentially silent, frequencies below about 16 kHz are unusable for our purposes. Also, given that audio equipment is usually designed for frequencies below about 20 kHz, our available bandwidth is limited to a 4 kHz range between 16 to 20 kHz. Due to practical / technical issues, the usable range becomes limited further to a usable range of around 3 kHz.

The effect of a 3 kHz bandwidth is that the sound quality is limited to be about the same as an old-school landline telephone.


This plug-in is entirely free for personal use in any manner, including commercial use, but is subject to the terms and conditions of GPL version 2 (or later).

If you wish to share this plug-in with others, please link to this post. This will ensure that everyone has access to the latest version.

Please DO NOT hotlink directly to the plug-in, as doing so is effectively stealing my (paid for) Internet bandwidth.

If you must share a downloaded versions of this plug-in, ensure that you include this copyright notice in full:

The plug-in:

Installation Instructions:

This plug-in may be used in Audacity version 2.3 or later.

Install into Audacity in the same way as any other Nyquist Plug-in. Instructions for the current version of Audacity can be found HERE.

Usage Instructions:

  • The speech to be encoded may be on a mono or stereo track.
  • The track sample rate MUST be 44100 Hz or higher.
  • The speech recording should be clear and not distorted. Ideally it should have a peak level around -3 dB.


  1. Select the audio to be encoded.
  2. Open the “Subliminal” effect from the Effect menu.
  3. Ensure that Encode is selected.
  4. Apply.


  1. Select the audio to be decoded.
  2. Open the “Subliminal” effect from the Effect menu.
  3. Ensure that Decode is selected.
  4. Apply.

14 thoughts on “Steganography and “Silent Subliminals””

  1. I am having an issue that every time I import something, the project rate is 24000. When I change it to 44100, it does not work. How do I fix this issue for all future projects?

    1. To prevent spam, comments do not appear until I approve them. I’ve been away for a few days for the funeral of a relative, so I’ve not been available to approve comments until now. I do try to respond to genuine comments as quickly as possible 😉

  2. Hi Steve,

    Got a couple questions on these plugins:

    1) How does this differ to the subliminal.ny file that edgar-rft posted on the audacity forum back in 2011?

    2) If i play a subliminal audio at say 16,500Hz i can very faintly notice the high pitch frequency , but if i play it at 17,500hz i notice nothing. I’ve been reading that as we age our ears deteriorate and at my age (28) the ear stops picking up frequencies at the 17,500 range on average. Therefore, does this mean my subconscious is not receiving the audio and i should therefore choose a frequency that i can only just hear faintly? I.e. 16,500hz instead? There is very little info on this out there and no good scientific studies i could find.

    Much appreciated

    1. > 1) How does this differ to the subliminal.ny file that edgar-rft posted on the audacity forum back in 2011?

      The code is a bit different, but basically it is the same effect.
      The main difference is that this plug-in also includes a decoder so that the “message” can be converted back to an audible signal.

      > and no good scientific studies i could find.
      I’ll leave it up to you to draw your own conclusions from that. It is certainly not for a lack of trying because many people have been trying for years to produce verifiable evidence, just as many people have been trying for years to prove the existence of the Loch Ness Monster and Bigfoot.

  3. Thanks for this. Do you think uploading to Spotify or YouTube removes the subliminal characteristics at all?

    1. I generally write the term “subliminal” in quote because it refers to a belief that certain kinds of inaudible sound have causative influence on the subconscious mind.
      Considering that advocates of homoeopathy believe that “homoeopathic remedies” are causative of medical benefits even when the solution is diluted to the point that none of the final product is chemically indistinguishable from the diluent, then advocates of “silent subliminals” may believe that they still work even if they are encoded in such a way that the “message” is no longer physically present.
      Regarding the physical encoded message, it is likely that the encoding process when uploading to YouTube or Spotify, will remove, or at least substantially reduce the encoded message, but I don’t think it’s my place to tell people what to believe or not believe.
      You can test if an uploaded “silent subliminal” still contains the “message” by downloading (or recording) from YouTube / Spotify and running it through the plug-in with the “decoder” option. I would expect the decoded message to be very weak or totally absent, but please do try it for yourself.

  4. When listening to a subliminal for more than 30 minutes produced with this plug-in, I feel discomfort in my ears, it is as if the audio is hurting my ears, I believe it is because of the frequency at 16000 hz. Is there any way to resolve this?

    1. I’d suggest that you either listen at a lower volume, or don’t listen at all.

      I’m not an audiologist, but I’d advise against listening to anything at very high volume levels.

    2. I managed to solve it, the problem was on my PC. I used a lite version of windows 10, and this ”lite” version was without the correct drivers, this absence of drivers can distort the subliminal, hurting the ear. I formatted windows, now I installed the full version of windows, imported the WAV audio to audacity, ran the plug-in, and now it doesn’t hurt my ears anymore. Thanks!

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