Listening to classical music increases heart rate variability, a measure of cardiac autonomic balance (in which increased levels reflect less stress and greater resilience), whereas listening to noise or rock music decreases heart rate variability (reflecting greater stress). true or false?

True

Explanation:

The heart rate is under the control of the autonomous nervous system. The sympathetic division of the autonomous nervous system serves to exhibit the flight or fight response by increasing the heart rate during stress conditions. The parasympathetic division of the autonomous nervous system has an antagonistic effect and serves to lower down the heart rate to restore the resting stage of the body.

Heart rate variability reflects the balance of effect of these two divisions of the autonomous nervous system on the heart rate. Constant intervals between the successive heartbeats reflect lower heart rate variability. It is a measure of higher stress and reduced ability of the body to withstand the stress conditions (the resilience).

External factors affect heart rate variability. For example, listening to the calm and peaceful classical music reduces the activity of sympathetic division and thereby increases the heart rate variability and resilience by allowing the person to stay calm in the stress conditions.

On the other hand, noise and rock music increases the control of sympathetic division on the heart rate and thereby decreases the heart rate variability.  

sorry, but you do not have posted the diagram.