This is not a whistle, so there’s no high to mid-pitch sound.  But it makes sounds like the airflow in a tube, such as when you purse your lip and blow out air from your mouth. The sound is soothing and relaxing and we recommend you to do this exercise where you feel comfortable.  The narrow tube promotes expansion of the lung while you blow in the necklace, allowing more oxygen to transfer to the lungs.  Unless other people are close within one arm's distance, it’s not a loud sound that can be heard from away.