Sonifying a human pulse to aid mindfulness meditation.
The goal of this project was to imagine a way in which biofeedback could be used to help with mindfulness meditation.
Master Digital Design
Pulse Sings is a biofeedback design that uses sound to convey information about your heart beat. Listening to your heart beat is more conducive to closed-eye, mindfulness meditation.
I was inspired to start this personal project after reading "The Sonification Handbook" by Thomas Hermann which discusses practical implementations of using sound to convey information. Also, I had recently purchased some biofeedback devices for my Arduino including a pulse sensor that I was eager to experiment with. After a quick brainstorm session, I came up with an idea of how I might drive sounds using a heart rate sensor as my input device.
I began researching in Google Scholar and PubMed to find out which heart rate parameters are used as health indicators. The heart beat information which I decided to use in Pulse Sings is called "heart rate variability" (HRV). HRV is the variance in time between consecutive heart beats. Below are some of my research discoveries regarding HRV and HRV therapy:
- HRV is often used as an indicator of psychological stress. Typically, lower HRV indicates higher stress levels and higher HRV indicates physical and mental well-being.
- HRV monitoring has been experimented with to aid mindfulness meditation
- HRV biofeedback training has been known to help regulate the stress of athletes during competitions
- Some studies have explored using HRV training as a way to treat anxiety and depression
HRV training typically uses something called a Poincare plot. A Poincare plot is a scatterplot that graphs the time intervals of your heart beat (RR intervals). The more spread out the points on the plot, the higher your HRV is.
"The Sonification Handbook" defines sonification as conveying information by using non-speech sounds. Sonifications are often used to supplement visual information displays in order to improve user experience. A practical example of a sonification is the increasing beeping sound that is used by most modern vehicles while reversing. The closer together the beeps get, the closer you are to an object behind you. The camera feed on your dashboard also conveys a lot of useful information, but the warning beeps ensure that you won't bump into something even if you aren't paying much attention.
The biggest drawback with Poincare plots is that they are not conducive to close-eye meditation. Staring at a bright screen for five or more minutes during a biofeedback session may also lead to increased anxiety, defeating the purpose of the training altogether.
- How might I reliably convey heart rate variability information off-screen using sound?
- How well will users interpret sonifications of HRV information compared to Poincare plot information or other visual indicators?
Ideation & validation
The biggest challenge during this project was choosing which sound parameters to represent HRV and ongoing changes in HRV. My initial plan was to user test different sound parameters, but due to the Covid-19 lockdown my access to users was limited. Trusting my gut instinct, I began experimenting with sounds in Max MSP while trying my best to strike a balance between pleasant sounds and sounds which were able to convey changing information.
I had a lot of fun testing the design with my eyes closed to see whether I could relax enough to influence the sounds. My partner also tested the design and is apparently much better at meditating than I am.
I decided to create a proof of concept video of the design to share with others to elicit their reactions. For the final prototype, I used a tremolo effect (modulating amplitude) to represent the distance in time between heart beats and changing pitch/timbre to signify whether overall HRV was moving up or down. I created a on-screen visualizer as this was necessary to best demonstrate the proof of concept.
I used the below technologies to create a working prototype for the Pulse Sings project:
- Cycling 74's Max
- Arduino Uno
- DF Robot's Gravity heart rate sensor
My future goals for the Pulse Sings design include:
- Implementing a wireless pulse sensor to enable users to more easily lie down while meditating
- Prototyping a mobile device version to allow for more freedom of movement
- Visualizing user progress over time