Understanding the acoustic signals produced by every heartbeat
Every heartbeat produces mechanical movements inside the heart. As valves open and close, they generate vibrations that propagate through the surrounding tissues of the chest.
These vibrations can be detected as sound. When doctors listen to the heart using a stethoscope, they are observing these acoustic signals.
These sounds contain valuable information about the rhythm and mechanical activity of the heart.
With modern smartphones, it is now possible to capture these signals digitally and analyze them as physiological data.
The two main heart sounds
During each cardiac cycle, two main sounds are typically produced. These are traditionally known as S1 and S2.
The first sound, S1, occurs when the valves between the atria and ventricles close. This marks the beginning of the phase where the ventricles contract and pump blood into the arteries.
The second sound, S2, occurs when the valves of the aorta and pulmonary artery close, marking the end of that contraction phase.
Together, these sounds form the familiar rhythm often described as “lub-dub”.
From heart sounds to rhythm analysis
Although heart sounds have traditionally been observed through a stethoscope, digital signal processing allows these acoustic events to be analyzed in new ways.
By recording the signal and detecting the timing of each heartbeat, it becomes possible to derive rhythm measurements such as:
- heart rate
- RR intervals
- rhythm variability
This transforms heart sounds from a purely auditory observation into a measurable physiological signal.
The phonocardiogram
When heart sounds are recorded and displayed as a signal over time, the result is called a phonocardiogram.
This graphical representation shows the acoustic structure of each heartbeat and allows timing relationships between beats to be studied.
Phonocardiography has been used in physiological research for decades, but modern mobile devices now make similar observations accessible outside specialized laboratories.
Listening with technology
Cardiomic applies this principle by using the smartphone microphone to capture heart sounds when the device is placed near the chest.
The recorded signal can then be processed to detect the timing of each heartbeat and reveal rhythm patterns that are not easily perceived by ear alone.
By transforming these acoustic vibrations into digital data, it becomes possible to explore the dynamics of heart rhythm through everyday technology.