The hunt was on. Thog shouted and waved at the charging woolly mammoth while Grok ran up from behind and lunged onto the behemoth's rump. He grasped its fur, climbed up its torso, and began to swing his flint blade high into the air. Just then, the animal reared up and threw Grok violently to the ground. Thog ran to Grok's motionless body.

Ever since caveman Thog put his ear to the chest of Grok to see if he was still alive, humans have harnessed the power of sound for medicine. Thog listened for sounds, such as a heartbeat or breath. Today, descendants of Thog are listening to and sending sound into the body for diagnosis, treatment, and healing.

Besides the humble but still useful stethoscope, ultrasound was one of the earliest methods of using sound to explore the body. Developed in the 1940s, it has progressed from a crude bistable representation (two electrical values, like on or off) to live moving images.

Biomedical acoustics, or the practice of directing acoustic waves into the body for measurement, is sometimes the best way to detect problems. Electrocardiograms (ECG) can't always detect all forms of cardiovascular disease, but analyzing acoustic waves can detect heart valve abnormalities.

One method of detecting cardiovascular disease is by attaching accelerometers and gyroscopes to the chest while filtering out other body noises, such as respiration and other residual sounds. Seismocardiograms (SCG) and gyrocardiograms (GCG) measure cardiovascular vibrations. Comparing the patient's cardiac vibrations to normal measurements, doctors can detect heart failure, circulation problems, coronary artery disease, and many other scary sounding diseases. These new methods are quickly replacing and complimenting traditional non-acoustical procedures.

Acoustical measurements of different parts of the body are helping respiratory patients. By narrowing and extracting sounds and vibrations from the areas of the chest, back, neck, and lips, doctors can detect constrictions and other issues. Asthma, sleep apnea, pneumonia, and COPD diagnoses are also benifiting from this advancing technology.

Biomedical acoustics can aid in monitoring and diagnosing gastrointestinal problems, nervous disorders like Parkinson's disease and multiple sclerosis, dysphagia, vocal disorders, osteoarthritis and chondromalacia.

We've explored listening to sounds bounced around inside the body, now let's actually manipulate the body using sound. Ultrasonography is the therapeutic use of ultrasound to control pain, sprains, muscle spasms, tissue injury, osteoarthritis, and other musculoskeletal issues. These devices use unfocused ultrasound waves (1 MHz to 8 MHz) to heat the affected area.

High intensity focused ultrasound has successfully been used to treat benign tumors,  cardiac ablation, and glaucoma. Low intensity ultrasonic devices (below 80 Hz) are used to break up and remove the eye lens during cataract surgery. Other surgical uses are to rapidly coagulate blood vessels, and to perform liposuction.

Medical researchers at Standford have been using sound for heart research. The experiments use Faraday waves (the ripples you might see in a beverage on a turbulent flight, train, or bus ride) to coral cells and mimic tightly-packed heart tissue. Scientists can then use these cardiac tissue samples in studies. They are inching closer to generating tissue patches that can replace damaged heart wall tissue.

Perhaps the most interesting recent medical advancement using sound is to treat liver cancer. HistoSonics has developed a system that uses fast, focused pulses of ultrasound to create a bubble in a tumor. The sound waves then liquify and destroy the tumor without harming the surrounding tissue. The technology is new and in trial, but they've successfully treated a patient with kidney cancer as well.

We've listened inside the body, we've zapped pain and tumors. Now let's heal not only other parts of the body, but the mind. Many people with sleep disorders, unconventional work shifts, noisy environments, and tinitus, rely on white noise to aid sleep. Something as simple as a fan, noise machine, or music can create a relaxed state and lead to sleep. One podcast, "Bore You To Sleep", offers uninteresting stories read in a flat tone with little to no personality. If you fall asleep listening, it's done its job.

Healing the body by controlling brain waves is a new science that is showing promising results. Our brains' electrical activity can be measured with an  electroencephalogram (EEG). Beta, Alpha, Theta, and Delta brain waves are present during different levels of activity, Beta being the most active and Delta the least. Brain waves, by their nature, are rhythmic frequencies. Theories currently revolve around the idea that brain waves can be changed to a healthier state through sound vibrations.

This isn't a new concept. For more than 40,000 years, Australia's aboriginal tribes have used the didgeridoo for healing. Tibetans use singing bowls in spiritual ceremonies. A "sound bath" is a popular full body relaxation technique using singing bowls, bells, and tuning forks.

And finally, we come full circle back to the stethoscope. But this one is a "brain stethoscope," as neurologist Josef Parvizi, MD, PhD likes to call it. He has harnessed brain waves to play music...sort of. His device, which looks like a headband, listens to brain waves and then produces tones from a speaker embedded in the headband. What he and his team have discovered is that there is a distinct difference in tones between normal brain activity and a seizure. Many seizures are obvious and manifest as convulsions. But non-convulsive subclinical seizures can be detected as well. Parvizi's vision is to have devices available to patients and parents who can then detect these small, but damaging episodes outside of the doctor's office. That's music to my ears.