Abstract: A method of estimating a number of lung function indices of an individual. The method includes: transmitting an ultrasound signal toward a chest of the individual from a speaker of a smartphone while the individual is holding the smartphone in a hand of the individual; receiving in a microphone of the smartphone a reflected signal reflected from the chest of the individual in response to the ultrasound signal; extracting a number of features from the reflected signal; and providing the number of features to a neural network regression model, wherein the neural network regression model estimates the number of lung function indices based on the number of features and based on a non-linear correlation between chest wall motion and human lung function.