I have this clip of a heartbeat being played and I am trying to manipulate the sound so when the volume is increased the beats don’t sound as if they are being heard through a stethoscope. I want the sounds to instead sound as they would if you were to put your ear to someone’s chest. Can anyone advise me on how I should manipulate the track to achieve this goal of eliminating the metallic sound?
Many Thanks!
I don’t get any metalic sound. It sounds like a perfectly normal heartbeat to me.
What are you listening on? I have a killer sound system and all of the sound is coming from my sub-woofer and bass speakers. If you’re on a computer sound system, you’re overloading it and listening to the speakers beat themselves to death. This is serious special effects work. Normal sound systems need not apply.
I did the analysis and most if not all of the sound is below 100Hz. That’s like earthquake territory that only dogs can hear.
If you look at the blue waves in Audacity, some of the peaks go all the way up to 1 and that’s as loud as they get without distortion, crunch, and clanking sounds
Koz
Don’t confuse that with theatrical heartbeat. When movies and television do heartbeats, we push the pitch of the sound up much higher so TV set speakers can deal with it. Don’t confuse that with reality.
You have an actual, real heartbeat. You may be able to pitch shift it up higher so it “sounds” real.
Koz
Okay, so the metallic sound arises because I’m running it through my low quality computer output with mediocre headphones. I have access to better equipment and I will certainly give it a shot there. My purpose for the heartbeat is in a production I’m working on and I was hoping to provide the designer and director a feel for what the effect clip will sound like. When I did so originally they made the comment that there is a metallic sound to it and I realized this only occurs after I increase the gain (which I did so they could hear the clip well.)
I will play with the clip on a better system to see if that on its own deals with the problem. Otherwise, you mention a pitch shift on the clip, can you explain or link me to more information on that and how I would apply it in this instance? I mean, pitch shift is a pretty self explanatory concept but I’m not ignorant to the fact that I don’t possess a vast amount of knowledge on differences in Hz, pitches, etc.
Load the clip and Effect > Change Pitch. A panel opens that lets you change pitch in whatever form you like. Percentage, Hz, or keys on the piano. One octave is half or double frequency.
Experiment with it. You need to be seriously higher than what you have to be theatrically useful. Most of the sound of theatrical heartbeat is in the rhythm, not the pitch.
Forgive me, I’m giving away all the movie secrets.
Koz
One option to increase the high frequency content (to make the heartbeat more audible) is to use the vocoder to mix your heartbeat with noise, e.g. attached. The result is like wooshy Doppler ultrasound …
Depending on the type of noise used you can add as much high frequencies as you like.
I’d suggest using brown noise, (no not that brown noise 
), rather than white noise which has way too much high frequency content for this purpose.
In Audacity 1.3 the noise generator is in “Generate” menu and the vocoder is near the bottom of the “Effect” menu, (scroll down to bottom of list).
So to bottom line this, you will be converting what you have, which appears to be the beat of a perfectly healthy human, into Something Else that’s more theatrically useful.
Those are two valid tools so far.
Koz
I really appreciate the help guys. I’ll most certainly keep playing around with it and see what I can come up with!
I had a minute to mess with this. This is the whole track just moved up one octave. Seven white piano keys.
That pitch shifted heartbeat sound has an interesting tense quality but it’s very synthetic: it’s like a robot with a low battery .
This (free) harmonic generator plugin for Audacity adds more high frequencies but still sounds natural, e.g. attached …
Nobody ever accused our pitch shifter of doing predictable, graceful things. That and it’s also pretty common knowledge that nothing good ever happens by pitch shifting more than two or three piano notes. I went seven. You might try combining two or more different pitch shifts and jockey the relative amounts of each one for theatrical effect.
By the way, this is very similar to Hollywood Earthquakes. You can’t film an earthquake, so theatrical earthquakes are always very different from real life. Or, I should say Hollywood earthquakes are a very tiny subset of real ones. You can’t film the rumble and the room moving, but you can film the wine glass tipping over. That’s only one of the three shocks.
Ever wonder why theatrical hospital rooms always have that beeping machine instead of a real pulse. That’s not accidental.
Koz