Sunday is Father's Day, and if there's anyone who needs a practical Father's day gift, it's new dads. That's why we reviewed the Android app Baby Sleep Instant, a free app (in-app purchases) that could help new dads with crying infants get some peace and quiet.

Baby Sleep Instant is an elegant, uncomplicated app that turns your smartphone or tablet into a low-frequency monotonous sound machine -- basically a white noise machine tuned to soothe babies who cry more than they get the rest they need.

The app comes with about a dozen sounds ranging from shower to fan to sea and stream to heartbeats, along with an option to record your own lullaby or sound if those built-in options don't do the trick. But judging from user testimonials, Baby Sleep Instant does the trick.

The concept isn't new. Neonatal units in hospitals have used low-frequency white noise to lull babies to sleep for a long time, and the concept has made it to the mainstream consumer market for new parents. In fact, a quick Google search of "baby sleep sound machines" produces dozens of different bedside sleep machines all intended to help new parents, and their infants, find some rest and relaxation.

But most of those machines range from $15 to $50, while Baby Sleep Instant is free on the Google Play store, with only in-app purchases that are probably unnecessary for most situations, anyway. Apple users can find similar equivalents available on iOS. 

As far as the app itself goes, there are a few things that stand out about Baby Sleep Instant.

First off, it's made by the Urbandroid Team, the same developers who created the critically acclaimed Sleep as Android app. That app (also freemium) uses the built-in accelerometer to turn any Android smartphone into a sleep-tracking device -- without the need for buying an accessory and slapping it to your wrist, though it can integrate with many smartwatches along with Philips HUE smartlights. It's also an alarm clock, sleep sound generator, and snore detector and recorder.

Suffice it to say, Urbandroid knows sleep tech. And they also know how to make an elegant app. Baby Sleep Instant has a simple, easy-to-understand interface that's fully and beautifully composed using Material Design principles, with the volume slider, play/stop buttons, and off-timer clearly visible on the main screen of any playback sound.

On the technical side, Baby Sleep Instant comes with a couple of very important minor features that help make sure your device is well-suited to the task. At the top, you'll see mute and airplane icons, which respectively turn off notifications and alarms, and make sure no disturbing interruptions can come from outside if you're using a smartphone.

One very important note about Baby Sleep Instant (and all uses of low-frequency monotonous sound machines or apps):

1.     Do not put any noise producing machines close to the baby, and especially not inside the crib -- inside the same room should be sufficient.

2.     Do not turn the volume up beyond 50 decibels. Keeping a soft volume is key for safety, but if you want to be scientific about it, use a decibel meter app.

3.     Do not leave the baby sleep sound going for extended periods of time.

That's because pediatric studies have found that baby sleep machines set louder than 50-decibels and/or situated too close to the infant can be dangerous for its hearing.

Baby Sleep Instant actually gives the same warning at startup, and it's good advice to follow to protect your infant's long-term hearing. While the most recent study tested only sleep machines and not apps, it's obvious the same rules apply.

But, in favor of Baby Sleep Instant and other apps, that study found that most standalone sleep machines' output volumes reached as much as 85 dB, much louder than even the loudest smartphones' speaker output.

Also in favor of Baby Sleep Instant (and for not paying any for premium features), is the fact that the sleep timer for the free version maxes out at 30 minutes -- and you should probably not leave a noise machine going for longer than that anyway. Check the Pediatrics sleep sound study here for all the details.

The one criticism of Baby Sleep Instant is that it only warns users about this important factor when it could have built some protections (similar to the airplane mode and notifications mute buttons) right into the app. How about a decibel meter built into the sound slider? Or maybe simply limiting the app's volume output to the level recommended by pediatricians?

Tap That App

With those important warnings (which apply to all noise machines and not just this app) and criticisms out of the way, we give Baby Sleep Instant a Tap That App recommendation.

It's free, it's easy, and it might give new dads (and moms) the gift of peace and quiet this Father's Day.