Hello, everyone. My name is Fusang zhang from Institute of Software, Chinese Academy of Sciences.
I would like to share our recent work on behalf of all authors.
The title of our paper is “Your Smart Speaker Can “Hear” Your Heartbeat!”.
This is the outline of this talk.
It consists of three parts.
Let’ s begin with background and motivation.
Vital sign monitoring is a common practice amongst medical professionals and plays a critical role in assisting clinical diagnosis, assessing the overall health of a patient.
Traditionally, dedicated equipment operated by professionals is used to monitor the vital signs.
For example, respiration is usually monitored by impedance photoplethysmography (PPG)
and heartbeat is monitored by electrocardiogram(ECG).
While the achieved accuracy is high,
these devices are usually expensive and need to be operated by professionals.
Smart speakers such as Amazon Echo and Google Home are becoming more and more popular in home environment.
Samsung and Huawei are also following this trend to launch their smart speaker products.
It was estimated that more than 200 million smart speakers have been sold
until the end of 2019 and this number continues to increase every year.
Wireless sensing becomes a hot research area
and a lot of wireless sensing-based vital sign monitoring systems are proposed.
So we have a question:
Can smart speaker become an platform to host this home health monitoring application?
The answer is yes，let see how to use acoustic signal to monitor heartbeat
Our system mainly consists of two main modules:
FMCW signal processing and heartbeat extraction.
The speaker transmits FMCW chirp signals.
These signals hit the target,
get reflected back and received by the microphone.
The first module FMCW signal processing:
there is a random time delay from the signal is triggered to be sent until the signal is actually sent out.
The second module is Heartbeat extraction:
the heartbeat information and the respiration information,
as well as the noise are mixed together.
We need to separate these signals.
There exists a system delay
when transmitting an audio signal using the smart speaker.
This is because the audio signal is put into a buffer first
and then transmitted out by the speaker.
This random delay can cause the reflection path to appear in front of
the direct path after the signal mixing and filtering operations.
So we carefully design a “virtual” transmission signal
and mix it with the received signal to cancel out the system delay.
If the heartbeat-induced chest displacement is 0.5 mm,
the phase change can be calculated as following Equation.
The phase change is around 16 degree.
However, one big challenge is that the phase change of the signal
caused by heartbeats is submerged by respiration-induced phase change.
Respiration produces 10 times larger chest displacement
than that produced by the heartbeat.
We observe that the heartbeat, respiration, and
even small body movement can induce phase variation of a signal.
We categorize different displacements of body movements
and their frequencies in the Table.
We employ a signal time-frequency analysis technique
that can decompose the signal into a superposition of independent frequency components.
To obtain heartbeat intervals,
we then employ a dynamic heartbeat segmentation scheme
by applying the EM algorithm.
As shown in Figure, we plot the segmentation results obtained.
It can be observed that
the segmented heartbeat intervals are consistent with the ground-truth ECG signals
with only a small 0.05 second average error.
Finally, we demonstrate our sensing system
To summary our work:
We enable smart speaker to monitor subtle human heartbeats
in a contact-free manner for the first time.
We believe the contact-free sensing
to achieve long-range through-wall human sensing.
realize more useful applications in our everyday lives.
Thank you for your attention.