"Yes. It is difficult to miss somebody and know they are where may be best," he agreed. Not that he'd experienced that too much. Usually it came down to him being where was best and safest, and missing his parents and home. But that was him leaving, not them.
He was confused by her own confusion, till she explained that she'd thought it was a piece of equipment. His head ducked in embarrassment, but at her request he slowly looked up.
"Er, yes, of course," he said, releasing his tentative attempt to control the noise. It was a relief, in all honesty, and he could feel himself relaxing thoroughly which helped with his shyness, even if it did make the low rumble more audible. "I'm uncertain as to it's purpose or meaning. It started when I smelled your anxiety, however, so I assume it is sympathetic. Which would quite match my feelings and intentions. It sounds slightly different than when I am happy, although due to my hearing it may not be different to humans."
He carefully took her hand and placed it on his chest, just to the side of his heart. "I believe this is the origin of the noise, though I've not been able to determine it's cause. It is loudest here, however."