measure (heart) beats per minute

Hello board,

I’m new to the forum and to Audacity. I have searched for an answer to the following question in the archives but have not found a response. Any help is greatly appreciated.

I have a consumer-level fetal heart monitor (doppler) that hooks into my mic jack on laptop. Audacity records nicely and each heart beat comes through clearly. I need to keep track of the baby’s heart beat (beats per minute). I can do this manually by counting peaks withing say a 15 sec time period then multiplying by 4, but I was wondering if there is an automated way for Audacity to identify and count peaks within a set time period.


That is the most accurate method (actually the most accurate method is to count for the full 60 seconds, but you get the idea.
I don’t think that anyone has bothered to write an automatic method as the manual method is so simple and reliable.

Thanks for the response, Steve. Good to know I didn’t miss something obvious in the program.

It does seem like it would be rather simple – for someone that has the know-how (not me) – to write a method that can keep count of the number of spikes beyond a defined threshold within a defined amount of time. Any college students out there need a class project? …

It’s worse than you think. Real-world events rarely lend themselves to neat, orderly digitizing. There is a tool in Audacity 1.3 called “Silent Finder.” What could be simpler, right? Sense when the blue waves go below a certain value and ring a metaphorical bell.

Most people mess around with the tool for months and then finally give up and cut the music or production by hand. Another option is let it the tool work and go back in later and clean up the damage – taking almost as long as doing it by hand in the first place.

You need the opposite of that tool.

There is a Music Finder, you might want to mess around with that. It still won’t give you the count, but it may clean up the work so another program can grab it.


If you do get the Music Finder to work and create a healthy square wave on the timeline, you can then use the spectrum analysis tool to find out the average frequency of the wave. The time or period is 1/frequency.

Aren’t you glad you asked?


Try this plug-in: