Visualizing heart sounds as a signal over time
A phonocardiogram is a graphical representation of the acoustic signals produced by the heart.
Each heartbeat generates mechanical vibrations when heart valves open and close. These vibrations propagate through the chest and can be detected as sound.
When these sounds are captured with a sensor and plotted as a signal over time, the resulting waveform is known as a phonocardiogram.
This representation allows the structure of heart sounds to be observed and analyzed using signal processing techniques.
From stethoscope to signal
Traditionally, heart sounds are examined using a stethoscope. Physicians listen to the acoustic events produced by the heart to evaluate aspects of cardiovascular function.
Phonocardiography extends this concept by recording these sounds and converting them into a visual signal.
Instead of relying only on hearing, researchers and clinicians can analyze the structure of heart sounds in a more systematic way.
This makes it possible to study timing relationships, amplitude patterns, and rhythmic structures within the cardiac cycle.
The structure of heart sounds
A typical phonocardiogram contains distinct acoustic events associated with each heartbeat.
The most prominent sounds are usually labeled S1 and S2.
S1 occurs when the valves between the atria and ventricles close, marking the start of ventricular contraction.
S2 occurs when the valves of the aorta and pulmonary artery close, marking the end of the contraction phase.
When plotted over time, these sounds create a repeating waveform that reflects the mechanical activity of the heart.
Observing heart rhythm through sound
Because each heartbeat produces identifiable acoustic events, phonocardiograms can also be used to determine the timing between beats.
By detecting these events in the signal, it becomes possible to estimate heart rate, RR intervals, and rhythm variability.
This transforms heart sounds into a measurable physiological signal that can be studied using computational methods.
Phonocardiography with smartphones
Modern smartphones contain sensitive microphones capable of capturing subtle acoustic signals.
When placed close to the chest, these microphones can record the vibrations produced by heartbeats.
Applications such as Cardiomic use these recordings to generate phonocardiogram-like signals and analyze the timing of heartbeats.
This allows everyday devices to function as digital instruments for observing cardiac rhythm patterns.