Frequency Shifting

I have a voice recording and I want to shift the frequency above 20,000Hz, so I can no longer hear it. Is there an app that can do that for me or do I have to create my own?


A voice recording is going to take up most if not all the frequencies between 20 and 20,000 although you could absolutely reduce the range to telephone frequencies 300-3000 if you didn’t care about the quality.

In the wide band version, you would create a “sound” channel with 20,000 to 40,000 covered with the new sound. In the case of the telephone sound you would map 300 to 20,000 so the high point would be 22700.

I wonder if you couldn’t do that with the Effect > Change Pitch tool. That’s trivial compared to the other problems you’ll have. You can’t use 44100 for a sample frequency. That only handles sounds perfectly up to about 17000.

You can’t analyze the result because the spectrum analyzer only goes up to 20,000. Etc.

What’s the job?


I am trying to create a subliminal audio message to help with my random dreams. They are random like the movie “The Ring”. For example, I’m not into sports and my dream was about practicing the high jump then was in a quest type game.

I see software on-line for subliminal messages but I also read that they are a scam. I understand the concept and the theory. I would like to do it myself so I can save the money. I know that it is possible, I just don’t know how. I have tried many audio software that said you can change the frequency, just not above the human ear.

Thanks for the reply,

An mp3 player / computer soundcard probably couldn’t produce ultrasound, and even if it could you couldn’t hear it whether you were awake or asleep.

Here is a plug-in for Audacity which produces audible sounds which allegedly alter ones metal state…

According to published research, listening to these beat frequencies can cause the main brainwave frequency to “align” with the beat frequencies through a phenomenon called entrainment. The beat frequencies might result in different states of awareness, including increased relaxation or alertness, > lucid dreaming > or many other states. The four most familiar brainwave frequencies are:

  • Beta (14-21 Hz and higher)
  • Alpha (7-14 Hz)
  • Theta (4-7 Hz)
  • Delta (0-4 Hz).

Research suggests there are many variations on these bands as well as additional brainwave frequencies, and that different states may be associated each.
By downloading, installing, using this plug-in and/or listening to the audio it generates, you explicitly accept full responsibility for any and all effects of its use, whether ‘positive’, ‘negative’, intentional, unintentional, or otherwise. This plug-in is meant for your own personal use and experimentation. No guarantee is offered that the user will experience any particular kind of effect from its use.

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Audacity can create files with frequencies up to 100 kHz, however, neither sound cards, CD players, audio amplifiers, loudspeakers headphones or other audio equipment are capable of reproducing such high frequencies. It would be possible (but probably very expensive) to build a device capable of playing ultrasonic audio files (using customised D/A converts, a specially designed amplifier and ultrasonic transducers), but the result would be inaudible. Just to add stress to Trebor’s comment, it’s not just that you can’t hear it consciously, it a limitation of the human physiology that ultrasonic frequencies cannot be heard at all (consciously or sub-consciously).

There are more plausible methods for creating subliminal messages, such as mixing a recoding of softly spoken words with broadband noise (such as wind or wave noise) so that the voice is on the threshold of being audible.

Thank you for all of your input. I will give the soft voice a try.

Thank you all again.

Okay, so subliminal don’t work while you are a sleep. Oh well.

Interesting Topic Subliminal Messaging - I have worked and played with numorous mp3’s for the likes of Sleep Learning, Gaining Confidence,Self Motivation etc I must confess was a skeptic but the sleep learning worked (took a while but and had to use the mp3 on my Ipod whilst I slept to get the best benefit - ear phones kept slipping out but I perseveared.
Self Motivation is a great Mp3 - if used over a 30 dat period it works fantasitic - I recommend - you can try for FREE.

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The effectiveness of your how-to-learn-spelling-while-you-sleep course is evident: it’s “fantasitic ”, I’m glad that you “perseveared.” with it.

Can you point me in the right direction to do what you attached in your response. About the phenomenon called entrainment.