The practical version
How to actually listen at home
Most of the gap between hearing something and hearing static has nothing to do with which app you installed. It is the room, the headphones and where the phone sits. Here is the whole setup, in the order that matters.
Hear what a real recording sounds like before you spend an evening trying.
Firstsong is not a medical device, it is not a doppler and it does not use ultrasound. It cannot tell you that your baby is well. If you notice fewer movements than usual, or any change in your baby's usual pattern, call your midwife or maternity unit now. Do not wait to try an app first.
Get the room right before you blame the app
A phone microphone was built to pick up a voice across a cafe. You are asking it for the quietest thing in the building, through several centimetres of you. Most people who say it never worked have never tried it under the conditions below.
- Kill every noise you control. Television off, fan off, extractor off, window shut. A washing machine two rooms away is much louder inside your abdomen than it is in your ears.
- Lie down and stay still. Sitting up tightens the abdominal wall and puts more between the microphone and the sound. Lying back, tilted slightly to one side, gives the flattest and quietest surface you have.
- Wait until you are calm. Straight after stairs your own pulse is fast and loud, which is the worst possible background for this.
- Go when you have felt movement. The last kick you felt is the best clue you have about where the baby is, and it expires quickly.
Wired headphones, and never the speaker
The phone microphone and the phone speaker are inches apart. Playing amplified belly sound out loud sends it straight back into the microphone, and what you hear is the room howling. Wired earbuds cost a few pounds and are the single biggest upgrade available to you. Bluetooth works but adds a delay, so what you hear lags what is happening under the phone.
Set your expectations while you are at it. The useful band is roughly 20 to 200 Hz, below almost everything you normally listen to, so a real recording sounds muffled, low and far away. Anything crisp and cinematic out of an app in this category is a filter making it pretty.
Where to put the phone
- Start low. In the third trimester the head is usually down and the heart sits low, so try below your navel and a little to one side, not up near your ribs.
- Follow the back. Sound carries best through the baby's back. If you know which side it is on, start there. If you do not, the side that feels like a broad firm surface is a fair guess, and kicks usually come from the other one.
- Skin, flat and gentle. Nothing between the phone and you, not even a thin shirt. Lay it flat rather than pressing hard, because pressure makes noise of its own.
- Know where the microphone is. On an iPhone it is on the bottom edge next to the charging port. That end is what needs contact with you.
- Move in small steps. Two centimetres at a time, and hold each position. Sweeping the phone around gives the engine nothing to lock onto.
How long to wait in each spot
Thirty seconds, then move. That is the shape of the engine: Firstsong will not print a heart rate until independent windows of the recording have agreed with each other for at least that long. Until they do you get a signal clarity meter instead of a number. Patience is genuinely the skill here, and it is the word that separates the five star reviews of this category from the one star ones.
The noise threshold comes from running the engine over the Shiraz University Fetal Heart Sounds Database with noise added until it broke. The thirty second rule is ours rather than a published finding. The ten control cases run before every deploy.
Hear what you are aiming for
Three real recordings from open research databases, analysed in your browser. One is a baby, one is a mother, and one has nothing in it. The first one tells you what to expect better than any description.
No account, no upload, no cookie.
Telling your own pulse apart
This is the thing that catches almost everybody. In the 1,995 reviews we read across 18 apps in this category, 171 describe hearing a heartbeat and having no idea whose it was, and my own heartbeat shows up as a phrase 103 times.
The reason it is so convincing is arithmetic. The largest app in this category puts it in its own FAQ: a baby runs at around twice the speed of yours. Double a resting adult pulse and you land squarely in the range people expect, so a slow strong rhythm can be reported back to you as a fast one and it will look exactly right.
- Take your own pulse while you listen. Fingers on your wrist, counting against what you hear. If they move together, that is you.
- Try the arm test. Put the phone on your forearm, or on a cushion, and see whether the app still finds a baby. Plenty of them do, and the reviews of this category are full of people discovering that their bed, their sofa and their hoodie all have a heartbeat. The full write up is here.
- Let the app do it. Firstsong reads your real pulse from your Apple Watch or your camera, refuses anything that matches it, and says so in words instead of leaving you guessing. The long version is here.
When nothing comes, which is often
Silence on any given evening is normal and it is not information about your baby. An anterior placenta sits between the microphone and the heart and muffles everything, which we wrote about here. Position changes hour to hour, and a noisy street does the rest.
So give it twenty minutes and then stop. Trying for two hours does not make a phone work better, it turns a nice idea into a bad night. And if what is worrying you is movement rather than sound, close the app and call. What silence actually means is here.
One email, the day it opens
Firstsong is not on the App Store yet. Leave an address and you get exactly one message when it is, with the price on the first line. No newsletter, no drip, no partner offers. You can reply to that email and a person reads it.
Stored on our own server, never sold, never shared. Your IP is hashed, not kept. Nothing about your pregnancy is asked for or stored.
Common questions
Do I really need to take my shirt off?
Yes. Even a thin cotton layer moves against the phone and against you, and that rustling is louder in the useful band than the heart you are chasing. Bare skin, phone flat, and hold still.
Does gel or oil help, like it does with a doppler?
No. Gel exists to couple an ultrasound beam into your body, and there is no beam here because nothing is transmitted. Oil around a charging port and a microphone is a bad idea for reasons that have nothing to do with your baby.
How long should the whole session take?
Twenty minutes is plenty and a good place to stop. Thirty seconds in each position, a few positions, and either it comes or it does not. The people who get results in this category talk about a quiet room and patience, and the ones who do not are usually sweeping the phone around for an hour.
Can I record it and keep it?
Yes, and it stays on your phone and in your own private iCloud. There is no account and nothing is uploaded, which is the only way we can honestly promise never to lose it.
I heard something but the app printed nothing. Why?
Because hearing something and proving it are different bars. The engine needs independent windows to agree before it shows a number, and a rhythm that comes and goes does not clear that bar. You can still keep the recording, and the honest label on it is that nobody knows what it was.
Keep reading
- Is it my heartbeat or the baby. the mistake almost everyone makes, and the arithmetic behind it
- Anterior placenta. why your belly sounds further away than everyone else's
- When you can hear it. what the public data shows, and where it runs out
- What a baby heartbeat app is. the category taken apart, from the microphone to the decision
Last checked 2026-08-23