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This clip demonstrates the modality sound. Again, we focus on the cardiovascular system: first, we listen to heart sounds and then measure blood pressure in the traditional (and precise) way by listening to the Korotkov sounds. However, we can also send sound into the body and measure its reflection to measure, for example, blood flow as demonstrated with the vascular Doppler.

This diagram shows the relation between the ECG, the pressure in the heart, the opening/closing of the valves and the resulting sounds S1/S2.

For heart diagnosis and other organs ultrasound is rapidly replacing the stethoscope because it gives you directly a realtime image of the heart. Check out the video clips on this excellent youTube channel about ultrasound.

Circuit diagram of the electronic stethoscope

The stethoscope uses an inverting amplifier which feeds into the USBDUX-sigma and into a mixing desk via a balanced XLR connection. The transformer is a standard mains print transformer which provides the balanced output and has excellent low frequency behaviour. The microphone is a standard electret condensor microphone from MAPLIN which was pushed over the tube from the stethoscope.

The oscilloscope trace of the audio signal was highpass filtered at 20Hz so that the trace roughly shows what can actually be heard but otherwise is left as it is with all artefacts. The ECG trace is Einthoven II and had only the 50Hz noise removed.

The headphone was plugged into the mixing desk so that Vasso could listen to both her own voice and to the sounds. Recordings were done on separate tracks, one for the bio-sounds and one for Vasso's voice.

The Doppler ultrasound was also fed into the mixing desk via a DI box.

We thank Peter Macfarlane for the constructive feedback on the script.

nonelec/sound.txt · Last modified: 2014/06/09 09:33 by berndporr