What about cats purring. "A cat’s purr vibrates within the range of 20-140 Hz, which can have many therapeutic benefits including lowering stress levels. That vibration can decrease the symptoms of dyspnea, also known as difficult or labored breathing. You can also reduce your cat’s dyspnea by stroking it — a win win situation!" https://www.hellahealth.com/blog/wellness/healing-power-purring-cat/#:~:text=A%20cat's%20purr%20vibrates%20within,it%20%E2%80%94%20a%20win%20win%20situation!