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Posted By Peter Bentley

My iStethoscope iphone application (which links to The Undercover Scientist book) continues to do extremely well in iTunes. It was the 11th most popular utility today out of over 700, with over 30,000 downloads in the last week. To celebrate I've created a second version which introduces a new listening mode: heartbeat pure. This uses different filtering to enable much clearer deep sounds, while removing all hiss and crackle. Although it may sound a little quieter that's because it's playing only the lower frequency sounds. I've found that it enables the 3G iphone to hear heartbeats much more reliably and count the heartrate much better than before. Using a good pair of headphones instead of the white earphones, you can also use the iphone like a real stethoscope and place it on your chest. (Remember the microphone is on the bottom, so that's the part that needs to be pressed to your chest.)

As before, for those interested, I'll explain how it works here. There are several minor updates in v1.1: The gain control at the bottom now automatically sets itself to the optimal level to help you listen without harming your ears. The first time the little undercover scientist appears, he gives instructions. I've adjusted the filter settings for "clear sound" to improve sensitivity. The link on the first screen to my book now works when you tap the name. But the main change is the new "heartbeat pure" mode. This uses an improved low- pass filter and no high pass filter at all. The result is that only very low frequency sounds remain audible and the resulting sound is much more pure and clean without any hiss. The 3G iphone suffered from hiss quite a lot, which prevented people from finding their heartbeats so easily and confused the heartrate monitor. Using this new mode, the heartrate monitor is much better, and it's much less fussy about accuracy with the microphone - you can still hear a heartbeat even if you are not so good at finding your pulse or artery. The downside to this change is that more processing is needed, so I had to increase the slight delay between the sound and playback fractionally compared to the last version. Users should also take care using the new "heartbeat pure" mode with volume and gain on maximum - if you brush against the microphone you may find the result very loud, and it might make the sound glitch a little. (You should restart the program if the sound continues to glitch.)

Hopefully everyone will enjoy the application, and remember that learning to find your pulse is a valuable skill. If you found the app interesting do please check out the popular science book that accompanies the program: The Undercover Scientist.

You can find more details about how the app works in the original blog entry.

Please leave a comment if you need help and I'll reply as soon as I can.

2 Comment(s):
Jimmy dereck said...
March 22, 2009 09:35:37
Peter Bentley said...
I have moved all old comments to the new support page. Please don't leave a comment here as I'm no longer checking old entries. If you'd like to leave a comment please go to the new support page:
February 8, 2009 17:18:50
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