# Ultrasound heartbeat in utero: actual sound or simulated? **URL:** \ **Category:** Factual Questions\ **Created:** [February 23, 2011, 8:37pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377 "2011-02-23T20:37:27Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![ShortBus](https://avatars.discourse-cdn.com/v4/letter/s/2bfe46/32.png) [@ShortBus](https://boards.straightdope.com/u/ShortBus)\ **Post date:** [February 23, 2011, 8:37pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/1 "2011-02-23T20:37:27Z")
My wife is pregnant for the first time and recently had an ultrasound where they played some audio that was supposedly the fetus’ heartbeat. My instinct tells me that an ultrasonic transducer would be incapable of doing this. A more likely explanation is that the machine generates an audio sample of a pseudo-heartbeat based on the measured contractions of the fetus’ heart. Can anyone clear this up? ---
**Author:** ![malkavia](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/malkavia/32/5621_2.png) [@malkavia](https://boards.straightdope.com/u/malkavia)\ **Post date:** [February 23, 2011, 8:47pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/2 "2011-02-23T20:47:42Z")
I have no answer for this, but this thread makes the “one tiny trick to lose belly fat” ad’s animated image of the lady whose belly keeps changing size quite adorable. Also, congrats! ---
**Author:** ![Omar\_Little](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/omar_little/32/269_2.png) [@Omar\_Little](https://boards.straightdope.com/u/Omar_Little)\ **Post date:** [February 23, 2011, 8:54pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/3 "2011-02-23T20:54:31Z")
I believe it is a simulated sound as you suggest. ---
**Author:** ![Shmendrik](https://avatars.discourse-cdn.com/v4/letter/s/ee7513/32.png) [@Shmendrik](https://boards.straightdope.com/u/Shmendrik)\ **Post date:** [February 23, 2011, 8:58pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/4 "2011-02-23T20:58:13Z")
I don’t think it’s simulated, because the Doppler makes all kinds of other sounds depending on what it’s pointed at. For some reason the placenta is a kind of windy whistling noise. ---
**Author:** ![thelabdude](https://avatars.discourse-cdn.com/v4/letter/t/dc4da7/32.png) [@thelabdude](https://boards.straightdope.com/u/thelabdude)\ **Post date:** [February 23, 2011, 9:42pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/5 "2011-02-23T21:42:12Z")
I think the doctors have long been able to hear the heartbeat with a stethoscope. The same microphone that picks up the ultrasound should be able to pick up the heartbeat. ---
**Author:** ![Giles](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/giles/32/60_2.png) [@Giles](https://boards.straightdope.com/u/Giles)\ **Post date:** [February 23, 2011, 9:55pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/6 "2011-02-23T21:55:08Z")
Back when I first heard one of my babies’ heartbeats, I got the impression that it was using a very sensitive microphone, because it made various extraneous noises as the nurse put it into position on my wife’s abdomen. That was more than 30 years ago – so the babies are no longer babies – but I don’t see why similar technology would not be used still. ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [February 23, 2011, 10:05pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/7 "2011-02-23T22:05:59Z")
I’m voting on semi-simulated. From this [Wikipedia](http://en.wikipedia.org/wiki/Doppler_fetal_monitor) page, it describes how a Fetal Doppler monitor works. My wife’s OB used one occasionally to check on the baby’s heartbeat, rather than do a full ultrasound. It does not make heartbeat noises based on an audio sample, but the circuitry generates sound based on what the doppler microphone picks up. When the heart beats, the ultrasonic sounds are reflected differently, and the speaker relays those differences in audio. ---
**Author:** ![Ca3799](https://avatars.discourse-cdn.com/v4/letter/c/9f8e36/32.png) [@Ca3799](https://boards.straightdope.com/u/Ca3799)\ **Post date:** [February 23, 2011, 11:56pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/8 "2011-02-23T23:56:00Z")
> [@Shmendrik](#): > > For some reason the placenta is a kind of windy whistling noise. That sound is called the ‘placental soufflé’. ---
**Author:** ![Ca3799](https://avatars.discourse-cdn.com/v4/letter/c/9f8e36/32.png) [@Ca3799](https://boards.straightdope.com/u/Ca3799)\ **Post date:** [February 23, 2011, 11:57pm UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/9 "2011-02-23T23:57:40Z")
Oh, and congratulations, Shortbus! ---
**Author:** ![MandaJo](https://avatars.discourse-cdn.com/v4/letter/m/ac91a4/32.png) [@MandaJo](https://boards.straightdope.com/u/MandaJo)\ **Post date:** [February 24, 2011, 12:53am UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/10 "2011-02-24T00:53:19Z")
How far along is your wife? I assume you are talking about an ultrasound, as you mentioned, not a doppler, as others are discussing. If you mean a 7-8 week, make-sure-the-baby-is-in-the-uterus ultrasound, then I am pretty sure that that is simulated, as you said. If you are talking about a doppler monitor, post 10 weeks, then I think that’s real, for a given value of “translated into electronic signals and then back to audio” real. Congrats! I am a little over six weeks pregnant myself, and a nervous wreck. Our first ultrasound (post conception–lots and lots before that!) is in a week. ---
**Author:** ![jfoote5](https://avatars.discourse-cdn.com/v4/letter/j/9fc348/32.png) [@jfoote5](https://boards.straightdope.com/u/jfoote5)\ **Post date:** [April 25, 2012, 12:48am UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/11 "2012-04-25T00:48:44Z")
Don’t know if any of you still care, but I found a more definitive answer to this. > **[What is a Doppler Fetal Monitor? (with pictures)](https://www.thehealthboard.com/what-is-a-doppler-fetal-monitor.htm)** > > A Doppler fetal monitor is a type of device that is commonly used in prenatal examinations to translate the sounds of a baby's... Essentially yes, it’s a simulation based on the Doppler effect. ---
**Author:** ![grude](https://avatars.discourse-cdn.com/v4/letter/g/e47774/32.png) [@grude](https://boards.straightdope.com/u/grude)\ **Post date:** [April 25, 2012, 1:16am UTC](https://boards.straightdope.com/t/ultrasound-heartbeat-in-utero-actual-sound-or-simulated/572377/12 "2012-04-25T01:16:46Z")
They may not be sold openly in the USA but my wife bought a cheap fetal doppler machine on ebay, once we found my son’s heartbeat it sounded exactly like at the OB. That is the real heartbeat the machine only amplifies the sound, we could also listen to the blood supply to the placenta or even bowel sounds and our own heart beats. If you are asking whether the sound is really that loud, well no of course not the machine is amplifying it.