# Recording with inaudible sounds

**URL:** <https://boards.straightdope.com/t/recording-with-inaudible-sounds/582983>\
**Category:** Factual Questions\
**Created:** [May 24, 2011, 5:00am UTC](https://boards.straightdope.com/t/recording-with-inaudible-sounds/582983 "2011-05-24T05:00:33Z")\
**Posts on this page:** 4\
**Page:** 2

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**Author:** ![casdave](https://avatars.discourse-cdn.com/v4/letter/c/c6cbf5/32.png) [@casdave](https://boards.straightdope.com/u/casdave)\
**Post date:** [May 28, 2011, 1:55pm UTC](https://boards.straightdope.com/t/recording-with-inaudible-sounds/582983/21 "2011-05-28T13:55:55Z")

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You could always record on tape at higher speed setting, and just playback at a lower speed

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**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\
**Post date:** [May 28, 2011, 2:05pm UTC](https://boards.straightdope.com/t/recording-with-inaudible-sounds/582983/22 "2011-05-28T14:05:24Z")

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> [@casdave](#):
>
> You could always record on tape at higher speed setting, and just playback at a lower speed

Won’t work. If a standard mic doesn’t pick up \<20hz, nothing will be on the tape, and tape recorders are not designed to record that range. And if the sound is already on the tape at \<20hz, playing it back slower will reduce the pitch farther below human hearing, making the inaudible even more inaudible.

What you probably meant to say was “record slow, play back fast.” That will only work if you can pick the sounds up and transfer to the tape in the first place.

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**Author:** ![ZenBeam](https://avatars.discourse-cdn.com/v4/letter/z/3ab097/32.png) [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)\
**Post date:** [May 28, 2011, 4:50pm UTC](https://boards.straightdope.com/t/recording-with-inaudible-sounds/582983/23 "2011-05-28T16:50:06Z")

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No, **casdave** has it right.

The OP wants to end up with sounds in the 12 to 17 Hz range. He can achieve this by recording sounds at 24 to 34 Hz, and playing them back at half speed. This helps with the microphone requirement, leaving only the playback requirement.

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**Author:** ![Musicat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/musicat/32/20189_2.png) [@Musicat](https://boards.straightdope.com/u/Musicat)\
**Post date:** [May 28, 2011, 4:55pm UTC](https://boards.straightdope.com/t/recording-with-inaudible-sounds/582983/24 "2011-05-28T16:55:04Z")

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> [@ZenBeam](#):
>
> No, **casdave** has it right.
> 
> The OP wants to end up with sounds in the 12 to 17 Hz range. He can achieve this by recording sounds at 24 to 34 Hz, and playing them back at half speed. This helps with the microphone requirement, leaving only the playback requirement.

Apparently, reading the OP’s subsequent posts, he doesn’t want to necessarily _record_ sub-20hz sounds, he just wants to _reproduce_ them. That’s different. Most HiFi amplifying equipment cuts off below 20hz, so that’s unlikely to work, either, unless he uses specialty sub-woofer devices.

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