What do you need to record heartbeat audio?
Many people are asking me about the audio setup I use to record the heartbeats of my models. After some personal experiments and the help of a professional audio editor (rhythmia.net) i can say that the audio we are recording now is of an exceptional good quality.
It all starts of course with the setup.
Below you can see some essential components for a good auscultation setup.
What do you need to record the heartbeat?
- Recording device: Zoom H5 or alternative
- Mic: Sennheiser MKE2 Lavalier or alternative
- Littmann stethoscope or alternative
As you can see, the head of the mic is a perfect fit for the stethoscope tube.
If you want to record audio + video together, my advice is to also use the line – out which you can find at the left side of the Zoom audio device (see picture below) and connect this with the audio input on the camera.
Using Line-out to connect with the camera
Using the line out gives you three advantages :
- The second audio signal is stored in the camera / DSLR. This gives you a secondary audio backup source.
- The second audio signal, coming from the line out and recorded in parallel with the video signal, can be synchronized later during post processing with the audio (stored) on the audio recorder (Zoom). This guarantees a perfect synchronization between audio and video.
- Some parts of the camera audio signal (which we got via the Line out) can be used later for mixing with the camera audio. This gives extra depth and richness to the heartbeat sounds.
Lastly, don’t forget to use the headset output too. This to avoid potential distortions. Stick to -12dB while recording.
Of course, removal of unwanted noises and other specific optimizations are done during the post editing phase. But starting with a clear and non-distorted audio signal at the start gives perfect audio at the end.
Length of the tube
We discovered that the tube length is important when recording loud hearts. We still need to do some further testing but it seems that a longer tube length (20-30cm) gives better results than a short one (3-5cm). The reason might be that louder hearts increase the pressure significantly at the side of the mic (where air cannot escape because the mic seals the tube). A constant inflow, due to the pressure of the heartbeats, might result in more distortion in the case there is not much tube available.